zshexpn - zsh expansion and substitution
The following types of expansions are performed in the indicated order in five
steps:
- History Expansion
- This is performed only in interactive shells.
- Alias Expansion
- Aliases are expanded immediately before the command line is parsed as
explained under Aliasing in zshmisc(1).
- Process Substitution
- Parameter Expansion
- Command Substitution
- Arithmetic Expansion
- Brace Expansion
- These five are performed in left-to-right fashion. On each argument, any
of the five steps that are needed are performed one after the other.
Hence, for example, all the parts of parameter expansion are completed
before command substitution is started. After these expansions, all
unquoted occurrences of the characters ` \',`'' and
`"' are removed.
- Filename Expansion
- If the SH_FILE_EXPANSION option is set, the order of expansion is
modified for compatibility with sh and ksh. In that case
filename expansion is performed immediately after alias
expansion, preceding the set of five expansions mentioned above.
- Filename Generation
- This expansion, commonly referred to as globbing, is always done
last.
The following sections explain the types of expansion in detail.
History expansion allows you to use words from previous command lines in the
command line you are typing. This simplifies spelling corrections and the
repetition of complicated commands or arguments.
Immediately before execution, each command is saved in the history list, the
size of which is controlled by the
HISTSIZE parameter. The one most
recent command is always retained in any case. Each saved command in the
history list is called a history
event and is assigned a number,
beginning with 1 (one) when the shell starts up. The history number that you
may see in your prompt (see EXPANSION OF PROMPT SEQUENCES in
zshmisc(1)) is the number that is to be assigned to the
next
command.
A history expansion begins with the first character of the
histchars
parameter, which is `
!' by default, and may occur anywhere on the
command line, including inside double quotes (but not inside single quotes
'...' or C-style quotes
$'...' nor when escaped with a
backslash).
The first character is followed by an optional event designator (see the section
`Event Designators') and then an optional word designator (the section `Word
Designators'); if neither of these designators is present, no history
expansion occurs.
Input lines containing history expansions are echoed after being expanded, but
before any other expansions take place and before the command is executed. It
is this expanded form that is recorded as the history event for later
references.
History expansions do not nest.
By default, a history reference with no event designator refers to the same
event as any preceding history reference on that command line; if it is the
only history reference in a command, it refers to the previous command.
However, if the option
CSH_JUNKIE_HISTORY is set, then every history
reference with no event specification
always refers to the previous
command.
For example, `
!' is the event designator for the previous command, so `
!!:1' always refers to the first word of the previous command, and `
!!$' always refers to the last word of the previous command. With
CSH_JUNKIE_HISTORY set, then `
!:1' and `
!$' function in
the same manner as `
!!:1' and `
!!$', respectively. Conversely,
if
CSH_JUNKIE_HISTORY is unset, then `
!:1' and `
!$' refer
to the first and last words, respectively, of the same event referenced by the
nearest other history reference preceding them on the current command line, or
to the previous command if there is no preceding reference.
The character sequence `
^foo^bar' (where `
^'
is actually the second character of the
histchars parameter) repeats
the last command, replacing the string
foo with
bar. More
precisely, the sequence `
^foo^bar^' is
synonymous with `
!!:s^foo^bar^',
hence other modifiers (see the section `Modifiers') may follow the final `
^'. In particular, `
^foo^bar^:G'
performs a global substitution.
If the shell encounters the character sequence `
!"' in the input,
the history mechanism is temporarily disabled until the current list (see
zshmisc(1)) is fully parsed. The `
!"' is removed from the
input, and any subsequent `
!' characters have no special significance.
A less convenient but more comprehensible form of command history support is
provided by the
fc builtin.
An event designator is a reference to a command-line entry in the history list.
In the list below, remember that the initial
`!' in each item may be
changed to another character by setting the
histchars parameter.
- !
- Start a history expansion, except when followed by a blank, newline, `
=' or ` ('. If followed immediately by a word designator
(see the section `Word Designators'), this forms a history reference with
no event designator (see the section `Overview').
- !!
- Refer to the previous command. By itself, this expansion repeats the
previous command.
- !n
- Refer to command-line n.
- !-n
- Refer to the current command-line minus n.
- !str
- Refer to the most recent command starting with str.
- !?str[?]
- Refer to the most recent command containing str. The trailing `
?' is necessary if this reference is to be followed by a modifier
or followed by any text that is not to be considered part of
str.
- !#
- Refer to the current command line typed in so far. The line is treated as
if it were complete up to and including the word before the one with the `
!#' reference.
- !{...}
- Insulate a history reference from adjacent characters (if necessary).
A word designator indicates which word or words of a given command line are to
be included in a history reference. A `
:' usually separates the event
specification from the word designator. It may be omitted only if the word
designator begins with a `
^', `
$', `
*', `
-' or
`
%'. Word designators include:
- 0
- The first input word (command).
- n
- The nth argument.
- ^
- The first argument. That is, 1.
- $
- The last argument.
- %
- The word matched by (the most recent) ?str search.
- x-y
- A range of words; x defaults to 0.
- *
- All the arguments, or a null value if there are none.
- x*
- Abbreviates `x-$'.
- x-
- Like `x*' but omitting word $.
Note that a `
%' word designator works only when used in one of `
!%', `
!:%' or `
!?str?:%', and only when
used after a
!? expansion (possibly in an earlier command). Anything
else results in an error, although the error may not be the most obvious one.
After the optional word designator, you can add a sequence of one or more of the
following modifiers, each preceded by a `
:'. These modifiers also work
on the result of
filename generation and
parameter expansion,
except where noted.
- a
- Turn a file name into an absolute path: prepends the current directory, if
necessary; remove ` .' path segments; and remove `..' path
segments and the segments that immediately precede them.
This transformation is agnostic about what is in the filesystem, i.e. is on the
logical, not the physical directory. It takes place in the same manner as when
changing directories when neither of the options
CHASE_DOTS or
CHASE_LINKS is set. For example, `
/before/here/../after' is
always transformed to `
/before/after', regardless of whether
`
/before/here' exists or what kind of object (dir, file, symlink, etc.)
it is.
- A
- Turn a file name into an absolute path as the `a' modifier does,
and then pass the result through the realpath(3) library
function to resolve symbolic links.
Note: on systems that do not have a
realpath(3) library function,
symbolic links are not resolved, so on those systems `
a' and `
A' are equivalent.
Note:
foo:A and
realpath(foo) are different on some inputs. For
realpath(foo) semantics, see the `
P` modifier.
- c
- Resolve a command name into an absolute path by searching the command path
given by the PATH variable. This does not work for commands
containing directory parts. Note also that this does not usually work as a
glob qualifier unless a file of the same name is found in the current
directory.
- e
- Remove all but the part of the filename extension following the
`.'; see the definition of the filename extension in the
description of the r modifier below. Note that according to that
definition the result will be empty if the string ends with a `
.'.
- h
- Remove a trailing pathname component, leaving the head. This works like `
dirname'.
- l
- Convert the words to all lowercase.
- p
- Print the new command but do not execute it. Only works with history
expansion.
- P
- Turn a file name into an absolute path, like realpath(3). The
resulting path will be absolute, have neither ` .' nor `..'
components, and refer to the same directory entry as the input
filename.
Unlike
realpath(3), non-existent trailing components are permitted and
preserved.
- q
- Quote the substituted words, escaping further substitutions. Works with
history expansion and parameter expansion, though for parameters it is
only useful if the resulting text is to be re-evaluated such as by
eval.
- Q
- Remove one level of quotes from the substituted words.
- r
- Remove a filename extension leaving the root name. Strings with no
filename extension are not altered. A filename extension is a ` .'
followed by any number of characters (including zero) that are neither `
.' nor `/' and that continue to the end of the string. For
example, the extension of ` foo.orig.c' is `.c', and
`dir.c/foo' has no extension.
- s/l/r[/]
- Substitute r for l as described below. The substitution is
done only for the first string that matches l. For arrays and for
filename generation, this applies to each word of the expanded text. See
below for further notes on substitutions.
The forms `
gs/l/r' and
`
s/l/r/:G' perform global substitution,
i.e. substitute every occurrence of
r for
l. Note that the
g or
:G must appear in exactly the position shown.
See further notes on this form of substitution below.
- &
- Repeat the previous s substitution. Like s, may be preceded
immediately by a g. In parameter expansion the & must
appear inside braces, and in filename generation it must be quoted with a
backslash.
- t
- Remove all leading pathname components, leaving the tail. This works like
` basename'.
- u
- Convert the words to all uppercase.
- x
- Like q, but break into words at whitespace. Does not work with
parameter expansion.
The
s/l/r/ substitution works as follows. By
default the left-hand side of substitutions are not patterns, but character
strings. Any character can be used as the delimiter in place of `
/'. A
backslash quotes the delimiter character. The character `
&', in
the right-hand-side
r, is replaced by the text from the left-hand-side
l. The `
&' can be quoted with a backslash. A null
l
uses the previous string either from the previous
l or from the
contextual scan string
s from `
!?s'. You can omit the
rightmost delimiter if a newline immediately follows
r; the rightmost `
?' in a context scan can similarly be omitted. Note the same record of
the last
l and
r is maintained across all forms of expansion.
Note that if a `
&' is used within glob qualifiers an extra backslash
is needed as a
& is a special character in this case.
Also note that the order of expansions affects the interpretation of
l
and
r. When used in a history expansion, which occurs before any other
expansions,
l and
r are treated as literal strings (except as
explained for
HIST_SUBST_PATTERN below). When used in parameter
expansion, the replacement of
r into the parameter's value is done
first, and then any additional process, parameter, command, arithmetic, or
brace references are applied, which may evaluate those substitutions and
expansions more than once if
l appears more than once in the starting
value. When used in a glob qualifier, any substitutions or expansions are
performed once at the time the qualifier is parsed, even before the `
:s' expression itself is divided into
l and
r sides.
If the option
HIST_SUBST_PATTERN is set,
l is treated as a pattern
of the usual form described in the section FILENAME GENERATION below. This can
be used in all the places where modifiers are available; note, however, that
in globbing qualifiers parameter substitution has already taken place, so
parameters in the replacement string should be quoted to ensure they are
replaced at the correct time. Note also that complicated patterns used in
globbing qualifiers may need the extended glob qualifier notation
(#q:s/ .../.../) in order for the shell to
recognize the expression as a glob qualifier. Further, note that bad patterns
in the substitution are not subject to the
NO_BAD_PATTERN option so
will cause an error.
When
HIST_SUBST_PATTERN is set,
l may start with a
# to
indicate that the pattern must match at the start of the string to be
substituted, and a
% may appear at the start or after an
# to
indicate that the pattern must match at the end of the string to be
substituted. The
% or
# may be quoted with two backslashes.
For example, the following piece of filename generation code with the
EXTENDED_GLOB option:
print *.c(#q:s/#%(#b)s(*).c/'S${match[1]}.C'/)
takes the expansion of
*.c and applies the glob qualifiers in the
(#q ...) expression, which consists of a substitution
modifier anchored to the start and end of each word (
#%). This turns
on backreferences (
(#b)), so that the parenthesised subexpression is
available in the replacement string as
${match[1]}. The replacement
string is quoted so that the parameter is not substituted before the start of
filename generation.
The following
f,
F,
w and
W modifiers work only with
parameter expansion and filename generation. They are listed here to provide a
single point of reference for all modifiers.
- f
- Repeats the immediately (without a colon) following modifier until the
resulting word doesn't change any more.
- F:expr:
- Like f, but repeats only n times if the expression
expr evaluates to n. Any character can be used instead of
the ` :'; if `(', `[', or `{' is used as the
opening delimiter, the closing delimiter should be ' )',
`]', or ` }', respectively.
- w
- Makes the immediately following modifier work on each word in the
string.
- W:sep:
- Like w but words are considered to be the parts of the string that
are separated by sep. Any character can be used instead of the `
:'; opening parentheses are handled specially, see above.
Each part of a command argument that takes the form `
<(list)', `
>(list)' or `
=( list)' is subject to process substitution. The
expression may be preceded or followed by other strings except that, to
prevent clashes with commonly occurring strings and patterns, the last form
must occur at the start of a command argument, and the forms are only expanded
when first parsing command or assignment arguments. Process substitutions may
be used following redirection operators; in this case, the substitution must
appear with no trailing string.
Note that `
<<(list)' is not a special syntax; it is
equivalent to `
< <(list)', redirecting standard
input from the result of process substitution. Hence all the following
documentation applies. The second form (with the space) is recommended for
clarity.
In the case of the
< or
> forms, the shell runs the commands
in
list as a subprocess of the job executing the shell command line. If
the system supports the
/dev/fd mechanism, the command argument is the
name of the device file corresponding to a file descriptor; otherwise, if the
system supports named pipes (FIFOs), the command argument will be a named
pipe. If the form with
> is selected then writing on this special
file will provide input for
list. If
< is used, then the file
passed as an argument will be connected to the output of the
list
process. For example,
paste <(cut -f1 file1) <(cut -f3 file2) |
tee >(process1) >(process2) >/dev/null
cuts fields 1 and 3 from the files
file1 and
file2 respectively,
pastes the results together, and sends it to the processes
process1 and
process2.
If
=(...) is used instead of
<(...), then the file passed as an argument will be
the name of a temporary file containing the output of the
list process.
This may be used instead of the
< form for a program that expects to
lseek (see
lseek(2)) on the input file.
There is an optimisation for substitutions of the form
=(<<<arg ), where
arg is a single-word
argument to the here-string redirection
<<<. This form
produces a file name containing the value of
arg after any
substitutions have been performed. This is handled entirely within the current
shell. This is effectively the reverse of the special form
$(<arg ) which treats
arg as a file name and
replaces it with the file's contents.
The
= form is useful as both the
/dev/fd and the named pipe
implementation of
<(...) have drawbacks. In the former
case, some programmes may automatically close the file descriptor in question
before examining the file on the command line, particularly if this is
necessary for security reasons such as when the programme is running setuid.
In the second case, if the programme does not actually open the file, the
subshell attempting to read from or write to the pipe will (in a typical
implementation, different operating systems may have different behaviour)
block for ever and have to be killed explicitly. In both cases, the shell
actually supplies the information using a pipe, so that programmes that expect
to lseek (see
lseek(2)) on the file will not work.
Also note that the previous example can be more compactly and efficiently
written (provided the
MULTIOS option is set) as:
paste <(cut -f1 file1) <(cut -f3 file2) \
> >(process1) > >(process2)
The shell uses pipes instead of FIFOs to implement the latter two process
substitutions in the above example.
There is an additional problem with
>(process); when
this is attached to an external command, the parent shell does not wait for
process to finish and hence an immediately following command cannot
rely on the results being complete. The problem and solution are the same as
described in the section
MULTIOS in
zshmisc(1). Hence in a
simplified version of the example above:
paste <(cut -f1 file1) <(cut -f3 file2) > >(process)
(note that no
MULTIOS are involved),
process will be run
asynchronously as far as the parent shell is concerned. The workaround is:
{ paste <(cut -f1 file1) <(cut -f3 file2) } > >(process)
The extra processes here are spawned from the parent shell which will wait for
their completion.
Another problem arises any time a job with a substitution that requires a
temporary file is disowned by the shell, including the case where `
&!' or `
&|' appears at the end of a command containing
a substitution. In that case the temporary file will not be cleaned up as the
shell no longer has any memory of the job. A workaround is to use a subshell,
for example,
as the forked subshell will wait for the command to finish then remove the
temporary file.
A general workaround to ensure a process substitution endures for an appropriate
length of time is to pass it as a parameter to an anonymous shell function (a
piece of shell code that is run immediately with function scope). For example,
this code:
() {
print File $1:
cat $1
} =(print This be the verse)
outputs something resembling the following
File /tmp/zsh6nU0kS:
This be the verse
The temporary file created by the process substitution will be deleted when the
function exits.
The character `
$' is used to introduce parameter expansions. See
zshparam(1) for a description of parameters, including arrays,
associative arrays, and subscript notation to access individual array
elements.
Note in particular the fact that words of unquoted parameters are not
automatically split on whitespace unless the option
SH_WORD_SPLIT is
set; see references to this option below for more details. This is an
important difference from other shells.
In the expansions discussed below that require a pattern, the form of the
pattern is the same as that used for filename generation; see the section
`Filename Generation'. Note that these patterns, along with the replacement
text of any substitutions, are themselves subject to parameter expansion,
command substitution, and arithmetic expansion. In addition to the following
operations, the colon modifiers described in the section `Modifiers' in the
section `History Expansion' can be applied: for example,
${i:s/foo/bar/} performs string substitution on the expansion of
parameter
$i.
In the following descriptions, `word' refers to a single word substituted on the
command line, not necessarily a space delimited word. With default options,
after the assignments:
array=("first word" "second word")
scalar="only word"
then
$array substitutes two words, `
first word' and `
second
word', and
$scalar substitutes a single word `
only word'.
This may be modified by explicit or implicit word-splitting, however. The full
rules are complicated and are noted at the end.
- ${name}
- The value, if any, of the parameter name is substituted. The braces
are required if the expansion is to be followed by a letter, digit, or
underscore that is not to be interpreted as part of name. In
addition, more complicated forms of substitution usually require the
braces to be present; exceptions, which only apply if the option
KSH_ARRAYS is not set, are a single subscript or any colon
modifiers appearing after the name, or any of the characters ` ^',
` =', `~', `#' or `+' appearing before the
name, all of which work with or without braces.
If
name is an array parameter, and the
KSH_ARRAYS option is not
set, then the value of each element of
name is substituted, one element
per word. Otherwise, the expansion results in one word only; with
KSH_ARRAYS, this is the first element of an array. No field splitting
is done on the result unless the
SH_WORD_SPLIT option is set. See also
the flags
= and
s:string:.
- ${+name}
- If name is the name of a set parameter `1' is substituted,
otherwise ` 0' is substituted.
- ${name-word}
- ${name:-word}
- If name is set, or in the second form is non-null, then substitute
its value; otherwise substitute word. In the second form
name may be omitted, in which case word is always
substituted.
- ${name+word}
- ${name:+word}
- If name is set, or in the second form is non-null, then substitute
word; otherwise substitute nothing.
- ${name=word}
- ${name:=word}
- ${name::=word}
- In the first form, if name is unset then set it to word; in
the second form, if name is unset or null then set it to
word; and in the third form, unconditionally set name to
word. In all forms, the value of the parameter is then
substituted.
- ${name?word}
- ${name:?word}
- In the first form, if name is set, or in the second form if
name is both set and non-null, then substitute its value;
otherwise, print word and exit from the shell. Interactive shells
instead return to the prompt. If word is omitted, then a standard
message is printed.
In any of the above expressions that test a variable and substitute an alternate
word, note that you can use standard shell quoting in the
word
value to selectively override the splitting done by the
SH_WORD_SPLIT
option and the
= flag, but not splitting by the
s:string: flag.
In the following expressions, when
name is an array and the substitution
is not quoted, or if the `
(@)' flag or the
name[@]
syntax is used, matching and replacement is performed on each array element
separately.
- ${name#pattern}
- ${name##pattern}
- If the pattern matches the beginning of the value of name,
then substitute the value of name with the matched portion deleted;
otherwise, just substitute the value of name. In the first form,
the smallest matching pattern is preferred; in the second form, the
largest matching pattern is preferred.
- ${name%pattern}
- ${name%%pattern}
- If the pattern matches the end of the value of name, then
substitute the value of name with the matched portion deleted;
otherwise, just substitute the value of name. In the first form,
the smallest matching pattern is preferred; in the second form, the
largest matching pattern is preferred.
- ${name:#pattern}
- If the pattern matches the value of name, then substitute
the empty string; otherwise, just substitute the value of name. If
name is an array the matching array elements are removed (use the `
(M)' flag to remove the non-matched elements).
- ${name:|arrayname}
- If arrayname is the name (N.B., not contents) of an array variable,
then any elements contained in arrayname are removed from the
substitution of name. If the substitution is scalar, either because
name is a scalar variable or the expression is quoted, the elements
of arrayname are instead tested against the entire expression.
- ${name:*arrayname}
- Similar to the preceding substitution, but in the opposite sense, so that
entries present in both the original substitution and as elements of
arrayname are retained and others removed.
- ${name:^arrayname}
- ${name:^^arrayname}
- Zips two arrays, such that the output array is twice as long as the
shortest (longest for ` :^^') of name and arrayname,
with the elements alternatingly being picked from them. For ` :^',
if one of the input arrays is longer, the output will stop when the end of
the shorter array is reached. Thus,
a=(1 2 3 4); b=(a b); print ${a:^b}
will output `
1 a 2 b'. For `
:^^', then the input is repeated
until all of the longer array has been used up and the above will output `
1 a 2 b 3 a 4 b'.
Either or both inputs may be a scalar, they will be treated as an array of
length 1 with the scalar as the only element. If either array is empty, the
other array is output with no extra elements inserted.
Currently the following code will output `
a b' and `
1' as two
separate elements, which can be unexpected. The second print provides a
workaround which should continue to work if this is changed.
a=(a b); b=(1 2); print -l "${a:^b}"; print -l "${${a:^b}}"
- ${name:offset}
- ${name:offset:length}
- This syntax gives effects similar to parameter subscripting in the form
$name[start,end], but is
compatible with other shells; note that both offset and
length are interpreted differently from the components of a
subscript.
If
offset is non-negative, then if the variable
name is a scalar
substitute the contents starting
offset characters from the first
character of the string, and if
name is an array substitute elements
starting
offset elements from the first element. If
length is
given, substitute that many characters or elements, otherwise the entire rest
of the scalar or array.
A positive
offset is always treated as the offset of a character or
element in
name from the first character or element of the array (this
is different from native zsh subscript notation). Hence 0 refers to the first
character or element regardless of the setting of the option
KSH_ARRAYS.
A negative offset counts backwards from the end of the scalar or array, so that
-1 corresponds to the last character or element, and so on.
When positive,
length counts from the
offset position toward the
end of the scalar or array. When negative,
length counts back from the
end. If this results in a position smaller than
offset, a diagnostic is
printed and nothing is substituted.
The option
MULTIBYTE is obeyed, i.e. the offset and length count
multibyte characters where appropriate.
offset and
length undergo the same set of shell substitutions as
for scalar assignment; in addition, they are then subject to arithmetic
evaluation. Hence, for example
print ${foo:3}
print ${foo: 1 + 2}
print ${foo:$(( 1 + 2))}
print ${foo:$(echo 1 + 2)}
all have the same effect, extracting the string starting at the fourth character
of
$foo if the substitution would otherwise return a scalar, or the
array starting at the fourth element if
$foo would return an array.
Note that with the option
KSH_ARRAYS $foo always returns a
scalar (regardless of the use of the offset syntax) and a form such as
${foo[*]:3} is required to extract elements of an array named
foo.
If
offset is negative, the
- may not appear immediately after the
: as this indicates the
${name:-word} form of substitution.
Instead, a space may be inserted before the
-. Furthermore, neither
offset nor
length may begin with an alphabetic character or
& as these are used to indicate history-style modifiers. To
substitute a value from a variable, the recommended approach is to precede it
with a
$ as this signifies the intention (parameter substitution can
easily be rendered unreadable); however, as arithmetic substitution is
performed, the expression
${var: offs} does work, retrieving the offset
from
$offs.
For further compatibility with other shells there is a special case for array
offset 0. This usually accesses the first element of the array. However, if
the substitution refers to the positional parameter array, e.g.
$@ or
$*, then offset 0 instead refers to
$0, offset 1 refers to
$1, and so on. In other words, the positional parameter array is
effectively extended by prepending
$0. Hence
${*:0:1}
substitutes
$0 and
${*:1:1} substitutes
$1.
- ${name/pattern/repl}
- ${name//pattern/repl}
- ${name:/pattern/repl}
- Replace the longest possible match of pattern in the expansion of
parameter name by string repl. The first form replaces just
the first occurrence, the second form all occurrences, and the third form
replaces only if pattern matches the entire string. Both
pattern and repl are subject to double-quoted substitution,
so that expressions like ${name/$opat/$npat} will work, but obey
the usual rule that pattern characters in $opat are not treated
specially unless either the option GLOB_SUBST is set, or
$opat is instead substituted as ${~opat}.
The
pattern may begin with a `
#', in which case the
pattern
must match at the start of the string, or `
%', in which case it must
match at the end of the string, or `
#%' in which case the
pattern must match the entire string. The
repl may be an empty
string, in which case the final `
/' may also be omitted. To quote the
final `
/' in other cases it should be preceded by a single backslash;
this is not necessary if the `
/' occurs inside a substituted
parameter. Note also that the `
#', `
%' and `
#% are not
active if they occur inside a substituted parameter, even at the start.
If, after quoting rules apply,
${name} expands to an array,
the replacements act on each element individually. Note also the effect of the
I and
S parameter expansion flags below; however, the flags
M,
R,
B,
E and
N are not useful.
For example,
foo="twinkle twinkle little star" sub="t*e" rep="spy"
print ${foo//${~sub}/$rep}
print ${(S)foo//${~sub}/$rep}
Here, the `
~' ensures that the text of
$sub is treated as a
pattern rather than a plain string. In the first case, the longest match for
t*e is substituted and the result is `
spy star', while in the
second case, the shortest matches are taken and the result is `
spy spy
lispy star'.
- ${#spec}
- If spec is one of the above substitutions, substitute the length in
characters of the result instead of the result itself. If spec is
an array expression, substitute the number of elements of the result. This
has the side-effect that joining is skipped even in quoted forms, which
may affect other sub-expressions in spec. Note that ` ^',
`=', and `~', below, must appear to the left of ` #'
when these forms are combined.
If the option
POSIX_IDENTIFIERS is not set, and
spec is a simple
name, then the braces are optional; this is true even for special parameters
so e.g.
$#- and
$#* take the length of the string
$- and
the array
$* respectively. If
POSIX_IDENTIFIERS is set, then
braces are required for the
# to be treated in this fashion.
- ${^spec}
- Turn on the RC_EXPAND_PARAM option for the evaluation of
spec; if the ` ^' is doubled, turn it off. When this option
is set, array expansions of the form
foo${xx}bar, where the parameter
xx is set to (a b c), are substituted with `
fooabar foobbar foocbar' instead of the default ` fooa b
cbar'. Note that an empty array will therefore cause all arguments to
be removed.
Internally, each such expansion is converted into the equivalent list for brace
expansion. E.g.,
${^var} becomes
{$var[1],$var[2],...
},
and is processed as described in the section `Brace Expansion' below: note,
however, the expansion happens immediately, with any explicit brace expansion
happening later. If word splitting is also in effect the
$var[N] may themselves be split into different list
elements.
- ${=spec}
- Perform word splitting using the rules for SH_WORD_SPLIT during the
evaluation of spec, but regardless of whether the parameter appears
in double quotes; if the ` =' is doubled, turn it off. This forces
parameter expansions to be split into separate words before substitution,
using IFS as a delimiter. This is done by default in most other
shells.
Note that splitting is applied to
word in the assignment forms of
spec before the assignment to
name is performed. This
affects the result of array assignments with the
A flag.
- ${~spec}
- Turn on the GLOB_SUBST option for the evaluation of spec; if
the ` ~' is doubled, turn it off. When this option is set, the
string resulting from the expansion will be interpreted as a pattern
anywhere that is possible, such as in filename expansion and filename
generation and pattern-matching contexts like the right hand side of the `
=' and `!=' operators in conditions.
In nested substitutions, note that the effect of the
~ applies to the
result of the current level of substitution. A surrounding pattern operation
on the result may cancel it. Hence, for example, if the parameter
foo
is set to
*,
${~foo//\*/*.c} is substituted by the pattern
*.c, which may be expanded by filename generation, but
${${~foo}//\*/*.c} substitutes to the string
*.c, which will not
be further expanded.
If a
${...
} type parameter expression or a
$(...
)
type command substitution is used in place of
name above, it is
expanded first and the result is used as if it were the value of
name.
Thus it is possible to perform nested operations:
${${foo#head}%tail}
substitutes the value of
$foo with both `
head' and `
tail'
deleted. The form with
$(...
) is often useful in combination
with the flags described next; see the examples below. Each
name or
nested
${...
} in a parameter expansion may also be followed by a
subscript expression as described in
Array Parameters in
zshparam(1).
Note that double quotes may appear around nested expressions, in which case only
the part inside is treated as quoted; for example,
${(f)"$(foo)"} quotes the result of
$(foo), but the
flag `
(f)' (see below) is applied using the rules for unquoted
expansions. Note further that quotes are themselves nested in this context;
for example, in
"${(@f)"$(foo)"}", there are two
sets of quotes, one surrounding the whole expression, the other (redundant)
surrounding the
$(foo) as before.
If the opening brace is directly followed by an opening parenthesis, the string
up to the matching closing parenthesis will be taken as a list of flags. In
cases where repeating a flag is meaningful, the repetitions need not be
consecutive; for example, `(
q%q%q)' means the same thing as the more
readable `(
%%qqq)'. The following flags are supported:
- #
- Evaluate the resulting words as numeric expressions and output the
characters corresponding to the resulting integer. Note that this form is
entirely distinct from use of the # without parentheses.
If the
MULTIBYTE option is set and the number is greater than 127 (i.e.
not an ASCII character) it is treated as a Unicode character.
- %
- Expand all % escapes in the resulting words in the same way as in
prompts (see EXPANSION OF PROMPT SEQUENCES in zshmisc(1)). If this
flag is given twice, full prompt expansion is done on the resulting words,
depending on the setting of the PROMPT_PERCENT, PROMPT_SUBST
and PROMPT_BANG options.
- @
- In double quotes, array elements are put into separate words. E.g., `
"${(@)foo}"' is equivalent to `
"${foo[@]}"' and ` "${(@)foo[1,2]}"' is
the same as ` "$foo[1]" "$foo[2]"'. This is
distinct from field splitting by the f, s or z
flags, which still applies within each array element.
- A
- Convert the substitution into an array expression, even if it otherwise
would be scalar. This has lower precedence than subscripting, so one level
of nested expansion is required in order that subscripts apply to array
elements. Thus ${${(A)name}[1]} yields the
full value of name when name is scalar.
This assigns an array parameter with `
${...
=...
}', `
${...
:=...
}' or `
${...
::=...
}'. If
this flag is repeated (as in `
AA'), assigns an associative array
parameter. Assignment is made before sorting or padding; if field splitting is
active, the
word part is split before assignment. The
name part
may be a subscripted range for ordinary arrays; when assigning an associative
array, the
word part
must be converted to an array, for example
by using `
${(AA)=name=...
}' to activate field
splitting.
Surrounding context such as additional nesting or use of the value in a scalar
assignment may cause the array to be joined back into a single string
again.
- a
- Sort in array index order; when combined with `O' sort in reverse
array index order. Note that ` a' is therefore equivalent to the
default but ` Oa' is useful for obtaining an array's elements in
reverse order.
- b
- Quote with backslashes only characters that are special to pattern
matching. This is useful when the contents of the variable are to be
tested using GLOB_SUBST, including the ${~...}
switch.
Quoting using one of the
q family of flags does not work for this purpose
since quotes are not stripped from non-pattern characters by
GLOB_SUBST. In other words,
pattern=${(q)str}
[[ $str = ${~pattern} ]]
works if
$str is `
a*b' but not if it is `
a b', whereas
pattern=${(b)str}
[[ $str = ${~pattern} ]]
is always true for any possible value of
$str.
- c
- With ${#name}, count the total number of characters
in an array, as if the elements were concatenated with spaces between
them. This is not a true join of the array, so other expressions used with
this flag may have an effect on the elements of the array before it is
counted.
- C
- Capitalize the resulting words. `Words' in this case refers to sequences
of alphanumeric characters separated by non-alphanumerics, not to
words that result from field splitting.
- D
- Assume the string or array elements contain directories and attempt to
substitute the leading part of these by names. The remainder of the path
(the whole of it if the leading part was not substituted) is then quoted
so that the whole string can be used as a shell argument. This is the
reverse of ` ~' substitution: see the section FILENAME EXPANSION
below.
- e
- Perform single word shell expansions, namely parameter expansion,
command substitution and arithmetic expansion, on the
result. Such expansions can be nested but too deep recursion may have
unpredictable effects.
- f
- Split the result of the expansion at newlines. This is a shorthand for `
ps:\n:'.
- F
- Join the words of arrays together using newline as a separator. This is a
shorthand for ` pj:\n:'.
- g:opts:
- Process escape sequences like the echo builtin when no options are given (
g::). With the o option, octal escapes don't take a leading
zero. With the c option, sequences like `^X' are also
processed. With the e option, processes `\M-t' and similar
sequences like the print builtin. With both of the o and e
options, behaves like the print builtin except that in none of these modes
is ` \c' interpreted.
- i
- Sort case-insensitively. May be combined with `n' or
`O'.
- k
- If name refers to an associative array, substitute the keys
(element names) rather than the values of the elements. Used with
subscripts (including ordinary arrays), force indices or keys to be
substituted even if the subscript form refers to values. However, this
flag may not be combined with subscript ranges. With the KSH_ARRAYS
option a subscript ` [*]' or `[@]' is needed to operate on
the whole array, as usual.
- L
- Convert all letters in the result to lower case.
- n
- Sort decimal integers numerically; if the first differing characters of
two test strings are not digits, sorting is lexical. Integers with more
initial zeroes are sorted before those with fewer or none. Hence the array
` foo1 foo02 foo2 foo3 foo20 foo23' is sorted into the order
shown. May be combined with ` i' or `O'.
- o
- Sort the resulting words in ascending order; if this appears on its own
the sorting is lexical and case-sensitive (unless the locale renders it
case-insensitive). Sorting in ascending order is the default for other
forms of sorting, so this is ignored if combined with ` a',
`i' or ` n'.
- O
- Sort the resulting words in descending order; `O' without
`a', ` i' or `n' sorts in reverse lexical order. May
be combined with ` a', `i' or `n' to reverse the
order of sorting.
- P
- This forces the value of the parameter name to be interpreted as a
further parameter name, whose value will be used where appropriate. Note
that flags set with one of the typeset family of commands (in
particular case transformations) are not applied to the value of
name used in this fashion.
If used with a nested parameter or command substitution, the result of that will
be taken as a parameter name in the same way. For example, if you have `
foo=bar' and `
bar=baz', the strings
${(P)foo},
${(P)${foo}}, and
${(P)$(echo bar)} will be expanded to `
baz'.
Likewise, if the reference is itself nested, the expression with the flag is
treated as if it were directly replaced by the parameter name. It is an error
if this nested substitution produces an array with more than one word. For
example, if `
name=assoc' where the parameter
assoc is an
associative array, then `
${${(P)name}[elt]}' refers to the element of
the associative subscripted `
elt'.
- q
- Quote characters that are special to the shell in the resulting words with
backslashes; unprintable or invalid characters are quoted using the
$'\ NNN' form, with separate quotes for each
octet.
If this flag is given twice, the resulting words are quoted in single quotes and
if it is given three times, the words are quoted in double quotes; in these
forms no special handling of unprintable or invalid characters is attempted.
If the flag is given four times, the words are quoted in single quotes
preceded by a
$. Note that in all three of these forms quoting is done
unconditionally, even if this does not change the way the resulting string
would be interpreted by the shell.
If a
q- is given (only a single
q may appear), a minimal form of
single quoting is used that only quotes the string if needed to protect
special characters. Typically this form gives the most readable output.
If a
q+ is given, an extended form of minmal quoting is used that causes
unprintable characters to be rendered using
$'...'. This
quoting is similar to that used by the output of values by the
typeset
family of commands.
- Q
- Remove one level of quotes from the resulting words.
- t
- Use a string describing the type of the parameter where the value of the
parameter would usually appear. This string consists of keywords separated
by hyphens (` -'). The first keyword in the string describes the
main type, it can be one of ` scalar', `array',
`integer', ` float' or `association'. The other
keywords describe the type in more detail:
- local
- for local parameters
- left
- for left justified parameters
- right_blanks
- for right justified parameters with leading blanks
- right_zeros
- for right justified parameters with leading zeros
- lower
- for parameters whose value is converted to all lower case when it is
expanded
- upper
- for parameters whose value is converted to all upper case when it is
expanded
- readonly
- for readonly parameters
- tag
- for tagged parameters
- export
- for exported parameters
- unique
- for arrays which keep only the first occurrence of duplicated values
- hide
- for parameters with the `hide' flag
- hideval
- for parameters with the `hideval' flag
- special
- for special parameters defined by the shell
- u
- Expand only the first occurrence of each unique word.
- U
- Convert all letters in the result to upper case.
- v
- Used with k, substitute (as two consecutive words) both the key and
the value of each associative array element. Used with subscripts, force
values to be substituted even if the subscript form refers to indices or
keys.
- V
- Make any special characters in the resulting words visible.
- w
- With ${#name}, count words in arrays or strings; the
s flag may be used to set a word delimiter.
- W
- Similar to w with the difference that empty words between repeated
delimiters are also counted.
- X
- With this flag, parsing errors occurring with the Q, e and
# flags or the pattern matching forms such as `
${name #pattern}' are reported. Without
the flag, errors are silently ignored.
- z
- Split the result of the expansion into words using shell parsing to find
the words, i.e. taking into account any quoting in the value. Comments are
not treated specially but as ordinary strings, similar to interactive
shells with the INTERACTIVE_COMMENTS option unset (however, see the
Z flag below for related options)
Note that this is done very late, even later than the `
(s)' flag. So to
access single words in the result use nested expansions as in `
${${(z)foo}[2]}'. Likewise, to remove the quotes in the resulting words
use `
${(Q)${(z)foo}}'.
- 0
- Split the result of the expansion on null bytes. This is a shorthand for `
ps:\0:'.
The following flags (except
p) are followed by one or more arguments as
shown. Any character, or the matching pairs `
(...
)', `
{...
}', `
[...
]', or `
<...
>',
may be used in place of a colon as delimiters, but note that when a flag takes
more than one argument, a matched pair of delimiters must surround each
argument.
- p
- Recognize the same escape sequences as the print builtin in string
arguments to any of the flags described below that follow this
argument.
Alternatively, with this option string arguments may be in the form
$var in which case the value of the variable is substituted.
Note this form is strict; the string argument does not undergo general
parameter expansion.
For example,
sep=:
val=a:b:c
print ${(ps.$sep.)val}
splits the variable on a
:.
- ~
- Strings inserted into the expansion by any of the flags below are to be
treated as patterns. This applies to the string arguments of flags that
follow ~ within the same set of parentheses. Compare with ~
outside parentheses, which forces the entire substituted string to be
treated as a pattern. Hence, for example,
[[ "?" = ${(~j.|.)array} ]]
treats `
|' as a pattern and succeeds if and only if
$array
contains the string `
?' as an element. The
~ may be repeated to
toggle the behaviour; its effect only lasts to the end of the parenthesised
group.
- j:string:
- Join the words of arrays together using string as a separator. Note
that this occurs before field splitting by the
s:string: flag or the SH_WORD_SPLIT
option.
- l:expr::string1::string2:
- Pad the resulting words on the left. Each word will be truncated if
required and placed in a field expr characters wide.
The arguments
:string1: and
:string2:
are optional; neither, the first, or both may be given. Note that the same
pairs of delimiters must be used for each of the three arguments. The space to
the left will be filled with
string1 (concatenated as often as needed)
or spaces if
string1 is not given. If both
string1 and
string2 are given,
string2 is inserted once directly to the left
of each word, truncated if necessary, before
string1 is used to produce
any remaining padding.
If either of
string1 or
string2 is present but empty, i.e. there
are two delimiters together at that point, the first character of
$IFS
is used instead.
If the
MULTIBYTE option is in effect, the flag
m may also be
given, in which case widths will be used for the calculation of padding;
otherwise individual multibyte characters are treated as occupying one unit of
width.
If the
MULTIBYTE option is not in effect, each byte in the string is
treated as occupying one unit of width.
Control characters are always assumed to be one unit wide; this allows the
mechanism to be used for generating repetitions of control characters.
- m
- Only useful together with one of the flags l or r or with
the # length operator when the MULTIBYTE option is in
effect. Use the character width reported by the system in calculating how
much of the string it occupies or the overall length of the string. Most
printable characters have a width of one unit, however certain Asian
character sets and certain special effects use wider characters; combining
characters have zero width. Non-printable characters are arbitrarily
counted as zero width; how they would actually be displayed will
vary.
If the
m is repeated, the character either counts zero (if it has zero
width), else one. For printable character strings this has the effect of
counting the number of glyphs (visibly separate characters), except for the
case where combining characters themselves have non-zero width (true in
certain alphabets).
- r:expr::string1::string2:
- As l, but pad the words on the right and insert string2
immediately to the right of the string to be padded.
Left and right padding may be used together. In this case the strategy is to
apply left padding to the first half width of each of the resulting words, and
right padding to the second half. If the string to be padded has odd width the
extra padding is applied on the left.
- s:string:
- Force field splitting at the separator string. Note that a
string of two or more characters means that all of them must match
in sequence; this differs from the treatment of two or more characters in
the IFS parameter. See also the = flag and the
SH_WORD_SPLIT option. An empty string may also be given in which
case every character will be a separate element.
For historical reasons, the usual behaviour that empty array elements are
retained inside double quotes is disabled for arrays generated by splitting;
hence the following:
line="one::three"
print -l "${(s.:.)line}"
produces two lines of output for
one and
three and elides the
empty field. To override this behaviour, supply the `
(@)' flag as
well, i.e.
"${(@s.:.)line}".
- Z:opts:
- As z but takes a combination of option letters between a following
pair of delimiter characters. With no options the effect is identical to
z. (Z+c+) causes comments to be parsed as a string and
retained; any field in the resulting array beginning with an unquoted
comment character is a comment. (Z+C+) causes comments to be parsed
and removed. The rule for comments is standard: anything between a word
starting with the third character of $HISTCHARS, default #,
up to the next newline is a comment. (Z+n+) causes unquoted
newlines to be treated as ordinary whitespace, else they are treated as if
they are shell code delimiters and converted to semicolons. Options are
combined within the same set of delimiters, e.g. (Z+Cn+).
- _:flags:
- The underscore (_) flag is reserved for future use. As of this
revision of zsh, there are no valid flags; anything following an
underscore, other than an empty pair of delimiters, is treated as an
error, and the flag itself has no effect.
The following flags are meaningful with the
${...
#...
} or
${...
%...
} forms. The
S and
I flags may
also be used with the
${...
/...
} forms.
- S
- Search substrings as well as beginnings or ends; with # start from
the beginning and with % start from the end of the string. With
substitution via ${.../...} or
${...//... }, specifies non-greedy matching, i.e.
that the shortest instead of the longest match should be replaced.
- I:expr:
- Search the exprth match (where expr evaluates to a number).
This only applies when searching for substrings, either with the S
flag, or with ${.../...} (only the exprth
match is substituted) or ${...//...} (all matches
from the exprth on are substituted). The default is to take the
first match.
The
exprth match is counted such that there is either one or zero matches
from each starting position in the string, although for global substitution
matches overlapping previous replacements are ignored. With the
${...
%...
} and
${...
%%...
} forms,
the starting position for the match moves backwards from the end as the index
increases, while with the other forms it moves forward from the start.
Hence with the string
which switch is the right switch for Ipswich?
substitutions of the form
${(
SI:N:)
string#w*ch} as
N increases
from 1 will match and remove `
which', `
witch', `
witch'
and `
wich'; the form using `
##' will match and remove `
which
switch is the right switch for Ipswich', `
witch is the right
switch for Ipswich', `
witch for Ipswich' and `
wich'.
The form using `
%' will remove the same matches as for `
#',
but in reverse order, and the form using `
%%' will remove the same
matches as for `
##' in reverse order.
- B
- Include the index of the beginning of the match in the result.
- E
- Include the index one character past the end of the match in the result
(note this is inconsistent with other uses of parameter index).
- M
- Include the matched portion in the result.
- N
- Include the length of the match in the result.
- R
- Include the unmatched portion in the result (the Rest).
Here is a summary of the rules for substitution; this assumes that braces are
present around the substitution, i.e.
${...}. Some
particular examples are given below. Note that the Zsh Development Group
accepts
no responsibility for any brain damage which may occur during
the reading of the following rules.
- 1. Nested substitution
- If multiple nested ${...} forms are present,
substitution is performed from the inside outwards. At each level, the
substitution takes account of whether the current value is a scalar or an
array, whether the whole substitution is in double quotes, and what flags
are supplied to the current level of substitution, just as if the nested
substitution were the outermost. The flags are not propagated up to
enclosing substitutions; the nested substitution will return either a
scalar or an array as determined by the flags, possibly adjusted for
quoting. All the following steps take place where applicable at all levels
of substitution.
Note that, unless the `
(P)' flag is present, the flags and any
subscripts apply directly to the value of the nested substitution; for
example, the expansion
${${foo}} behaves exactly the same as
${foo}. When the `
(P)' flag is present in a nested
substitution, the other substitution rules are applied to the value
before it is interpreted as a name, so
${${(P)foo}} may differ
from
${(P)foo}.
At each nested level of substitution, the substituted words undergo all forms of
single-word substitution (i.e. not filename generation), including command
substitution, arithmetic expansion and filename expansion (i.e. leading
~ and
=). Thus, for example,
${${:-=cat}:h} expands to
the directory where the
cat program resides. (Explanation: the internal
substitution has no parameter but a default value
=cat, which is
expanded by filename expansion to a full path; the outer substitution then
applies the modifier
:h and takes the directory part of the
path.)
- 2. Internal parameter flags
- Any parameter flags set by one of the typeset family of commands,
in particular the -L, -R, -Z, -u and -l
options for padding and capitalization, are applied directly to the
parameter value. Note these flags are options to the command, e.g. `
typeset -Z'; they are not the same as the flags used within
parameter substitutions.
At the outermost level of substitution, the `
(P)' flag (rule
4.)
ignores these transformations and uses the unmodified value of the parameter
as the name to be replaced. This is usually the desired behavior because
padding may make the value syntactically illegal as a parameter name, but if
capitalization changes are desired, use the
${${(P)foo}} form (rule
25.).
- 3. Parameter subscripting
- If the value is a raw parameter reference with a subscript, such as
${ var[3]}, the effect of subscripting is applied
directly to the parameter. Subscripts are evaluated left to right;
subsequent subscripts apply to the scalar or array value yielded by the
previous subscript. Thus if var is an array, ${var[1][2]} is
the second character of the first word, but ${var[2,4][2]} is the
entire third word (the second word of the range of words two through four
of the original array). Any number of subscripts may appear. Flags such as
` (k)' and `(v)' which alter the result of subscripting are
applied.
- 4. Parameter name replacement
- At the outermost level of nesting only, the `(P)' flag is applied.
This treats the value so far as a parameter name (which may include a
subscript expression) and replaces that with the corresponding value. This
replacement occurs later if the ` (P)' flag appears in a nested
substitution.
If the value so far names a parameter that has internal flags (rule
2.),
those internal flags are applied to the new value after replacement.
- 5. Double-quoted joining
- If the value after this process is an array, and the substitution appears
in double quotes, and neither an ` (@)' flag nor a `#'
length operator is present at the current level, then words of the value
are joined with the first character of the parameter $IFS, by
default a space, between each word (single word arrays are not modified).
If the ` (j)' flag is present, that is used for joining instead of
$IFS.
- 6. Nested subscripting
- Any remaining subscripts (i.e. of a nested substitution) are evaluated at
this point, based on whether the value is an array or a scalar. As with
3., multiple subscripts can appear. Note that ${foo[2,4][2]}
is thus equivalent to ${${foo[2,4]}[2]} and also to
"${${(@)foo[2,4]}[2]}" (the nested substitution returns
an array in both cases), but not to "${${foo[2,4]}[2]}"
(the nested substitution returns a scalar because of the quotes).
- 7. Modifiers
- Any modifiers, as specified by a trailing `#', `%',
`/' (possibly doubled) or by a set of modifiers of the form `
:...' (see the section `Modifiers' in the section `History
Expansion'), are applied to the words of the value at this level.
- 8. Character evaluation
- Any `(#)' flag is applied, evaluating the result so far numerically
as a character.
- 9. Length
- Any initial `#' modifier, i.e. in the form
${#var}, is used to evaluate the length of the
expression so far.
- 10. Forced joining
- If the `(j)' flag is present, or no `(j)' flag is present
but the string is to be split as given by rule 11., and joining did
not take place at rule 5., any words in the value are joined
together using the given string or the first character of $IFS if
none. Note that the ` (F)' flag implicitly supplies a string for
joining in this manner.
- 11. Simple word splitting
- If one of the `(s)' or `(f)' flags are present, or the
`=' specifier was present (e.g. ${=var}), the
word is split on occurrences of the specified string, or (for =
with neither of the two flags present) any of the characters in
$IFS.
If no `
(s)', `
(f)' or `
=' was given, but the word is not
quoted and the option
SH_WORD_SPLIT is set, the word is split on
occurrences of any of the characters in
$IFS. Note this step, too,
takes place at all levels of a nested substitution.
- 12. Case modification
- Any case modification from one of the flags `(L)', `(U)' or
` (C)' is applied.
- 13. Escape sequence replacement
- First any replacements from the `(g)' flag are performed, then any
prompt-style formatting from the ` (%)' family of flags is
applied.
- 14. Quote application
- Any quoting or unquoting using `(q)' and `(Q)' and related
flags is applied.
- 15. Directory naming
- Any directory name substitution using `(D)' flag is applied.
- 16. Visibility enhancement
- Any modifications to make characters visible using the `(V)' flag
are applied.
- 17. Lexical word splitting
- If the '(z)' flag or one of the forms of the '(Z)' flag is
present, the word is split as if it were a shell command line, so that
quotation marks and other metacharacters are used to decide what
constitutes a word. Note this form of splitting is entirely distinct from
that described by rule 11.: it does not use $IFS, and does
not cause forced joining.
- 18. Uniqueness
- If the result is an array and the `(u)' flag was present, duplicate
elements are removed from the array.
- 19. Ordering
- If the result is still an array and one of the `(o)' or
`(O)' flags was present, the array is reordered.
- 20. RC_EXPAND_PARAM
- At this point the decision is made whether any resulting array elements
are to be combined element by element with surrounding text, as given by
either the RC_EXPAND_PARAM option or the `^' flag.
- 21. Re-evaluation
- Any `(e)' flag is applied to the value, forcing it to be
re-examined for new parameter substitutions, but also for command and
arithmetic substitutions.
- 22. Padding
- Any padding of the value by the `(l.fill.)' or `
(r. fill.)' flags is applied.
- 23. Semantic joining
- In contexts where expansion semantics requires a single word to result,
all words are rejoined with the first character of IFS between. So
in ` ${(P)${(f)lines}}' the value of ${lines}
is split at newlines, but then must be joined again before the `
(P)' flag can be applied.
If a single word is not required, this rule is skipped.
- 24. Empty argument removal
- If the substitution does not appear in double quotes, any resulting
zero-length argument, whether from a scalar or an element of an array, is
elided from the list of arguments inserted into the command line.
Strictly speaking, the removal happens later as the same happens with other
forms of substitution; the point to note here is simply that it occurs after
any of the above parameter operations.
- 25. Nested parameter name replacement
- If the `(P)' flag is present and rule 4. has not applied,
the value so far is treated as a parameter name (which may include a
subscript expression) and replaced with the corresponding value, with
internal flags (rule 2.) applied to the new value.
The flag
f is useful to split a double-quoted substitution line by line.
For example,
${(f)"$(<file)"} substitutes
the contents of
file divided so that each line is an element of the
resulting array. Compare this with the effect of
$(<file ) alone, which divides the file up by
words, or the same inside double quotes, which makes the entire content of the
file a single string.
The following illustrates the rules for nested parameter expansions. Suppose
that
$foo contains the array
(bar baz):
- "${(@)${foo}[1]}"
- This produces the result b. First, the inner substitution
"${foo}", which has no array ( @) flag, produces a
single word result "bar baz". The outer substitution
"${(@)...[1]}" detects that this is a scalar, so that
(despite the ` (@)' flag) the subscript picks the first
character.
- "${${(@)foo}[1]}"
- This produces the result `bar'. In this case, the inner
substitution "${(@)foo}" produces the array `(bar
baz )'. The outer substitution "${...[1]}"
detects that this is an array and picks the first word. This is similar to
the simple case "${foo[1]}".
As an example of the rules for word splitting and joining, suppose
$foo
contains the array `
(ax1 bx1)'. Then
- ${(s/x/)foo}
- produces the words `a', `1 b' and `1'.
- ${(j/x/s/x/)foo}
- produces `a', `1', `b' and `1'.
- ${(s/x/)foo%%1*}
- produces `a' and ` b' (note the extra space). As
substitution occurs before either joining or splitting, the operation
first generates the modified array (ax bx), which is joined
to give "ax bx", and then split to give `a', `
b' and `'. The final empty string will then be elided, as it is not in
double quotes.
A command enclosed in parentheses preceded by a dollar sign, like `
$(...
)', or quoted with grave accents, like `
`...
`', is replaced with its standard output, with any trailing
newlines deleted. If the substitution is not enclosed in double quotes, the
output is broken into words using the
IFS parameter. The substitution `
$(cat foo)' may be replaced by the equivalent but faster
`
$(<foo)'. In either case, if the option
GLOB_SUBST is set, the output is eligible for filename generation.
A string of the form `
$[exp]' or `
$((exp))' is substituted with the value of the arithmetic
expression
exp.
exp is subjected to
parameter expansion,
command substitution and
arithmetic expansion before it is
evaluated. See the section `Arithmetic Evaluation'.
A string of the form `
foo{xx,yy,zz
}bar' is expanded to the individual words `
fooxxbar',
`
fooyybar' and `
foozzbar'. Left-to-right order is preserved.
This construct may be nested. Commas may be quoted in order to include them
literally in a word.
An expression of the form `
{n1..n2}', where
n1 and
n2 are integers, is expanded to every number between
n1 and
n2 inclusive. If either number begins with a zero, all
the resulting numbers will be padded with leading zeroes to that minimum
width, but for negative numbers the
- character is also included in the
width. If the numbers are in decreasing order the resulting sequence will also
be in decreasing order.
An expression of the form `
{n1..n2..n3 }', where
n1,
n2, and
n3 are integers, is expanded as above, but
only every
n3th number starting from
n1 is output. If
n3
is negative the numbers are output in reverse order, this is slightly
different from simply swapping
n1 and
n2 in the case that the
step
n3 doesn't evenly divide the range. Zero padding can be specified
in any of the three numbers, specifying it in the third can be useful to pad
for example `
{-99..100..01}' which is not possible to specify by
putting a 0 on either of the first two numbers (i.e. pad to two characters).
An expression of the form `
{c1..c2}', where
c1 and
c2 are single characters (which may be multibyte
characters), is expanded to every character in the range from
c1 to
c2 in whatever character sequence is used internally. For characters
with code points below 128 this is US ASCII (this is the only case most users
will need). If any intervening character is not printable, appropriate
quotation is used to render it printable. If the character sequence is
reversed, the output is in reverse order, e.g. `
{d..a}' is substituted
as `
d c b a'.
If a brace expression matches none of the above forms, it is left unchanged,
unless the option
BRACE_CCL (an abbreviation for `brace character
class') is set. In that case, it is expanded to a list of the individual
characters between the braces sorted into the order of the characters in the
ASCII character set (multibyte characters are not currently handled). The
syntax is similar to a
[...
] expression in filename generation:
`
-' is treated specially to denote a range of characters, but
`
^' or `
!' as the first character is treated normally. For
example, `
{abcdef0-9}' expands to 16 words
0 1 2 3 4 5 6 7 8 9 a b
c d e f.
Note that brace expansion is not part of filename generation (globbing); an
expression such as
*/{foo,bar} is split into two separate words
*/foo and
*/bar before filename generation takes place. In
particular, note that this is liable to produce a `no match' error if
either of the two expressions does not match; this is to be contrasted
with
*/(foo|bar), which is treated as a single pattern but otherwise
has similar effects.
To combine brace expansion with array expansion, see the
${^spec} form described in the section Parameter
Expansion above.
Each word is checked to see if it begins with an unquoted `
~'. If it
does, then the word up to a `
/', or the end of the word if there is no
`
/', is checked to see if it can be substituted in one of the ways
described here. If so, then the `
~' and the checked portion are
replaced with the appropriate substitute value.
A `
~' by itself is replaced by the value of
$HOME. A `
~'
followed by a `
+' or a `
-' is replaced by current or previous
working directory, respectively.
A `
~' followed by a number is replaced by the directory at that position
in the directory stack. `
~0' is equivalent to `
~+', and `
~1' is the top of the stack. `
~+' followed by a number is
replaced by the directory at that position in the directory stack. `
~+0' is equivalent to `
~+', and `
~+1' is the top of the
stack. `
~-' followed by a number is replaced by the directory that
many positions from the bottom of the stack. `
~-0' is the bottom of
the stack. The
PUSHD_MINUS option exchanges the effects of `
~+'
and `
~-' where they are followed by a number.
If the function
zsh_directory_name exists, or the shell variable
zsh_directory_name_functions exists and contains an array of function
names, then the functions are used to implement dynamic directory naming. The
functions are tried in order until one returns status zero, so it is important
that functions test whether they can handle the case in question and return an
appropriate status.
A `
~' followed by a string
namstr in unquoted square brackets is
treated specially as a dynamic directory name. Note that the first unquoted
closing square bracket always terminates
namstr. The shell function is
passed two arguments: the string
n (for name) and
namstr. It
should either set the array
reply to a single element which is the
directory corresponding to the name and return status zero (executing an
assignment as the last statement is usually sufficient), or it should return
status non-zero. In the former case the element of reply is used as the
directory; in the latter case the substitution is deemed to have failed. If
all functions fail and the option
NOMATCH is set, an error results.
The functions defined as above are also used to see if a directory can be turned
into a name, for example when printing the directory stack or when expanding
%~ in prompts. In this case each function is passed two arguments: the
string
d (for directory) and the candidate for dynamic naming. The
function should either return non-zero status, if the directory cannot be
named by the function, or it should set the array reply to consist of two
elements: the first is the dynamic name for the directory (as would appear
within `
~[...]'), and the second is the prefix length of
the directory to be replaced. For example, if the trial directory is
/home/myname/src/zsh and the dynamic name for
/home/myname/src
(which has 16 characters) is
s, then the function sets
The directory name so returned is compared with possible static names for parts
of the directory path, as described below; it is used if the prefix length
matched (16 in the example) is longer than that matched by any static name.
It is not a requirement that a function implements both
n and
d
calls; for example, it might be appropriate for certain dynamic forms of
expansion not to be contracted to names. In that case any call with the first
argument
d should cause a non-zero status to be returned.
The completion system calls `
zsh_directory_name c' followed by
equivalent calls to elements of the array
zsh_directory_name_functions,
if it exists, in order to complete dynamic names for directories. The code for
this should be as for any other completion function as described in
zshcompsys(1).
As a working example, here is a function that expands any dynamic names
beginning with the string
p: to directories below
/home/pws/perforce. In this simple case a static name for the directory
would be just as effective.
zsh_directory_name() {
emulate -L zsh
setopt extendedglob
local -a match mbegin mend
if [[ $1 = d ]]; then
# turn the directory into a name
if [[ $2 = (#b)(/home/pws/perforce/)([^/]##)* ]]; then
typeset -ga reply
reply=(p:$match[2] $(( ${#match[1]} + ${#match[2]} )) )
else
return 1
fi
elif [[ $1 = n ]]; then
# turn the name into a directory
[[ $2 != (#b)p:(?*) ]] && return 1
typeset -ga reply
reply=(/home/pws/perforce/$match[1])
elif [[ $1 = c ]]; then
# complete names
local expl
local -a dirs
dirs=(/home/pws/perforce/*(/:t))
dirs=(p:${^dirs})
_wanted dynamic-dirs expl 'dynamic directory' compadd -S\] -a dirs
return
else
return 1
fi
return 0
}
A `
~' followed by anything not already covered consisting of any number
of alphanumeric characters or underscore (`
_'), hyphen (`
-'),
or dot (`
.') is looked up as a named directory, and replaced by the
value of that named directory if found. Named directories are typically home
directories for users on the system. They may also be defined if the text
after the `
~' is the name of a string shell parameter whose value
begins with a `
/'. Note that trailing slashes will be removed from the
path to the directory (though the original parameter is not modified).
It is also possible to define directory names using the
-d option to the
hash builtin.
When the shell prints a path (e.g. when expanding
%~ in prompts or when
printing the directory stack), the path is checked to see if it has a named
directory as its prefix. If so, then the prefix portion is replaced with a `
~' followed by the name of the directory. The shorter of the two ways
of referring to the directory is used, i.e. either the directory name or the
full path; the name is used if they are the same length. The parameters
$PWD and
$OLDPWD are never abbreviated in this fashion.
If a word begins with an unquoted `
=' and the
EQUALS option is
set, the remainder of the word is taken as the name of a command. If a command
exists by that name, the word is replaced by the full pathname of the command.
Filename expansion is performed on the right hand side of a parameter
assignment, including those appearing after commands of the
typeset
family. In this case, the right hand side will be treated as a colon-separated
list in the manner of the
PATH parameter, so that a `
~' or an
`
=' following a `
:' is eligible for expansion. All such
behaviour can be disabled by quoting the `
~', the `
=', or the
whole expression (but not simply the colon); the
EQUALS option is also
respected.
If the option
MAGIC_EQUAL_SUBST is set, any unquoted shell argument in
the form `
identifier=expression' becomes eligible for
file expansion as described in the previous paragraph. Quoting the first `
=' also inhibits this.
If a word contains an unquoted instance of one of the characters `
*',
`
(', `
|', `
<', `
[', or `
?', it is
regarded as a pattern for filename generation, unless the
GLOB option
is unset. If the
EXTENDED_GLOB option is set, the `
^' and
`
#' characters also denote a pattern; otherwise they are not treated
specially by the shell.
The word is replaced with a list of sorted filenames that match the pattern. If
no matching pattern is found, the shell gives an error message, unless the
NULL_GLOB option is set, in which case the word is deleted; or unless
the
NOMATCH option is unset, in which case the word is left unchanged.
In filename generation, the character `
/' must be matched explicitly;
also, a `
.' must be matched explicitly at the beginning of a pattern
or after a `
/', unless the
GLOB_DOTS option is set. No filename
generation pattern matches the files `
.' or `
..'. In other
instances of pattern matching, the `
/' and `
.' are not treated
specially.
- *
- Matches any string, including the null string.
- ?
- Matches any character.
- [...]
- Matches any of the enclosed characters. Ranges of characters can be
specified by separating two characters by a ` -'. A ` -' or
` ]' may be matched by including it as the first character in the
list. There are also several named classes of characters, in the form `
[:name:]' with the following meanings. The first set
use the macros provided by the operating system to test for the given
character combinations, including any modifications due to local language
settings, see ctype(3):
- [:alnum:]
- The character is alphanumeric
- [:alpha:]
- The character is alphabetic
- [:ascii:]
- The character is 7-bit, i.e. is a single-byte character without the top
bit set.
- [:blank:]
- The character is a blank character
- [:cntrl:]
- The character is a control character
- [:digit:]
- The character is a decimal digit
- [:graph:]
- The character is a printable character other than whitespace
- [:lower:]
- The character is a lowercase letter
- [:print:]
- The character is printable
- [:punct:]
- The character is printable but neither alphanumeric nor whitespace
- [:space:]
- The character is whitespace
- [:upper:]
- The character is an uppercase letter
- [:xdigit:]
- The character is a hexadecimal digit
Another set of named classes is handled internally by the shell and is not
sensitive to the locale:
- [:IDENT:]
- The character is allowed to form part of a shell identifier, such as a
parameter name
- [:IFS:]
- The character is used as an input field separator, i.e. is contained in
the IFS parameter
- [:IFSSPACE:]
- The character is an IFS white space character; see the documentation for
IFS in the zshparam(1) manual page.
- [:INCOMPLETE:]
- Matches a byte that starts an incomplete multibyte character. Note that
there may be a sequence of more than one bytes that taken together form
the prefix of a multibyte character. To test for a potentially incomplete
byte sequence, use the pattern ` [[:INCOMPLETE:]]*'. This will
never match a sequence starting with a valid multibyte character.
- [:INVALID:]
- Matches a byte that does not start a valid multibyte character. Note this
may be a continuation byte of an incomplete multibyte character as any
part of a multibyte string consisting of invalid and incomplete multibyte
characters is treated as single bytes.
- [:WORD:]
- The character is treated as part of a word; this test is sensitive to the
value of the WORDCHARS parameter
Note that the square brackets are additional to those enclosing the whole set of
characters, so to test for a single alphanumeric character you need `
[[:alnum:]]'. Named character sets can be used alongside other types,
e.g. `
[[:alpha:]0-9]'.
- [^...]
- [!...]
- Like [...], except that it matches any character which is
not in the given set.
- <[x]-[y]>
- Matches any number in the range x to y, inclusive. Either of
the numbers may be omitted to make the range open-ended; hence `
<->' matches any number. To match individual digits, the
[... ] form is more efficient.
Be careful when using other wildcards adjacent to patterns of this form; for
example,
<0-9>* will actually match any number whatsoever at the
start of the string, since the `
<0-9>' will match the first
digit, and the `
*' will match any others. This is a trap for the
unwary, but is in fact an inevitable consequence of the rule that the longest
possible match always succeeds. Expressions such as `
<0-9>[^[:digit:]]*' can be used instead.
- (...)
- Matches the enclosed pattern. This is used for grouping. If the
KSH_GLOB option is set, then a ` @', `*', `+',
` ?' or `!' immediately preceding the ` (' is treated
specially, as detailed below. The option SH_GLOB prevents bare
parentheses from being used in this way, though the KSH_GLOB option
is still available.
Note that grouping cannot extend over multiple directories: it is an error to
have a `
/' within a group (this only applies for patterns used in
filename generation). There is one exception: a group of the form
(pat /)# appearing as a complete path segment can match a
sequence of directories. For example,
foo/(a*/)#bar matches
foo/bar,
foo/any/bar,
foo/any/anyother/bar, and so
on.
- x|y
- Matches either x or y. This operator has lower precedence
than any other. The ` |' character must be within parentheses, to
avoid interpretation as a pipeline. The alternatives are tried in order
from left to right.
- ^x
- (Requires EXTENDED_GLOB to be set.) Matches anything except the
pattern x. This has a higher precedence than ` /', so
`^foo/bar' will search directories in ` .' except
`./foo' for a file named ` bar'.
- x~y
- (Requires EXTENDED_GLOB to be set.) Match anything that matches the
pattern x but does not match y. This has lower precedence
than any operator except ` |', so ` */*~foo/bar' will search
for all files in all directories in ` .' and then exclude `
foo/bar' if there was such a match. Multiple patterns can be
excluded by ` foo~bar~baz'. In the
exclusion pattern ( y), `/' and `.' are not treated
specially the way they usually are in globbing.
- x#
- (Requires EXTENDED_GLOB to be set.) Matches zero or more
occurrences of the pattern x. This operator has high precedence; `
12#' is equivalent to `1(2#)', rather than ` (12)#'.
It is an error for an unquoted ` #' to follow something which
cannot be repeated; this includes an empty string, a pattern already
followed by ` ##', or parentheses when part of a KSH_GLOB
pattern (for example, ` !(foo)#' is invalid and must
be replaced by ` *(!(foo))').
- x##
- (Requires EXTENDED_GLOB to be set.) Matches one or more occurrences
of the pattern x. This operator has high precedence; ` 12##'
is equivalent to ` 1(2##)', rather than ` (12)##'. No more
than two active ` #' characters may appear together. (Note the
potential clash with glob qualifiers in the form ` 1(2##)' which
should therefore be avoided.)
If the
KSH_GLOB option is set, the effects of parentheses can be modified
by a preceding `
@', `
*', `
+', `
?' or `
!'.
This character need not be unquoted to have special effects, but the `
(' must be.
- @(...)
- Match the pattern in the parentheses. (Like `(...)'.)
- *(...)
- Match any number of occurrences. (Like `(...)#', except that
recursive directory searching is not supported.)
- +(...)
- Match at least one occurrence. (Like `(...)##', except that
recursive directory searching is not supported.)
- ?(...)
- Match zero or one occurrence. (Like `(|...)'.)
- !(...)
- Match anything but the expression in parentheses. (Like `
(^(...))'.)
The precedence of the operators given above is (highest) `
^',
`
/', `
~', `
|' (lowest); the remaining operators are
simply treated from left to right as part of a string, with `
#' and
`
##' applying to the shortest possible preceding unit (i.e. a
character, `
?', `
[...
]', `
<...
>',
or a parenthesised expression). As mentioned above, a `
/' used as a
directory separator may not appear inside parentheses, while a `
|'
must do so; in patterns used in other contexts than filename generation (for
example, in
case statements and tests within `
[[...
]]'),
a `
/' is not special; and `
/' is also not special after a `
~' appearing outside parentheses in a filename pattern.
There are various flags which affect any text to their right up to the end of
the enclosing group or to the end of the pattern; they require the
EXTENDED_GLOB option. All take the form
(#X) where
X may have one of the following forms:
- i
- Case insensitive: upper or lower case characters in the pattern match
upper or lower case characters.
- l
- Lower case characters in the pattern match upper or lower case characters;
upper case characters in the pattern still only match upper case
characters.
- I
- Case sensitive: locally negates the effect of i or l from
that point on.
- b
- Activate backreferences for parenthesised groups in the pattern; this does
not work in filename generation. When a pattern with a set of active
parentheses is matched, the strings matched by the groups are stored in
the array $match, the indices of the beginning of the matched
parentheses in the array $mbegin, and the indices of the end in the
array $mend, with the first element of each array corresponding to
the first parenthesised group, and so on. These arrays are not otherwise
special to the shell. The indices use the same convention as does
parameter substitution, so that elements of $mend and
$mbegin may be used in subscripts; the KSH_ARRAYS option is
respected. Sets of globbing flags are not considered parenthesised groups;
only the first nine active parentheses can be referenced.
For example,
foo="a string with a message"
if [[ $foo = (a|an)' '(#b)(*)' '* ]]; then
print ${foo[$mbegin[1],$mend[1]]}
fi
prints `
string with a'. Note that the first parenthesis is before the
(#b) and does not create a backreference.
Backreferences work with all forms of pattern matching other than filename
generation, but note that when performing matches on an entire array, such as
${array#pattern}, or a global substitution,
such as
${param//pat/repl},
only the data for the last match remains available. In the case of global
replacements this may still be useful. See the example for the
m flag
below.
The numbering of backreferences strictly follows the order of the opening
parentheses from left to right in the pattern string, although sets of
parentheses may be nested. There are special rules for parentheses followed by
`
#' or `
##'. Only the last match of the parenthesis is
remembered: for example, in `
[[ abab = (#b)([ab])# ]]', only the final
`
b' is stored in
match[1]. Thus extra parentheses may be
necessary to match the complete segment: for example, use `
X((ab|cd)#)Y' to match a whole string of either `
ab' or
`
cd' between `
X' and `
Y', using the value of
$match[1] rather than
$match[2].
If the match fails none of the parameters is altered, so in some cases it may be
necessary to initialise them beforehand. If some of the backreferences fail to
match -- which happens if they are in an alternate branch which fails to
match, or if they are followed by
# and matched zero times -- then the
matched string is set to the empty string, and the start and end indices are
set to -1.
Pattern matching with backreferences is slightly slower than without.
- B
- Deactivate backreferences, negating the effect of the b flag from
that point on.
- cN,M
- The flag (#cN,M) can be used anywhere
that the # or ## operators can be used except in the
expressions ` (*/)#' and `(*/)##' in filename generation,
where ` /' has special meaning; it cannot be combined with other
globbing flags and a bad pattern error occurs if it is misplaced. It is
equivalent to the form {N,M} in regular
expressions. The previous character or group is required to match between
N and M times, inclusive. The form
(#cN) requires exactly N matches;
(#c,M) is equivalent to specifying N as 0;
(#c N,) specifies that there is no maximum limit on
the number of matches.
- m
- Set references to the match data for the entire string matched; this is
similar to backreferencing and does not work in filename generation. The
flag must be in effect at the end of the pattern, i.e. not local to a
group. The parameters $MATCH, $MBEGIN and $MEND will
be set to the string matched and to the indices of the beginning and end
of the string, respectively. This is most useful in parameter
substitutions, as otherwise the string matched is obvious.
For example,
arr=(veldt jynx grimps waqf zho buck)
print ${arr//(#m)[aeiou]/${(U)MATCH}}
forces all the matches (i.e. all vowels) into uppercase, printing `
vEldt
jynx grImps wAqf zhO bUck'.
Unlike backreferences, there is no speed penalty for using match references,
other than the extra substitutions required for the replacement strings in
cases such as the example shown.
- M
- Deactivate the m flag, hence no references to match data will be
created.
- anum
- Approximate matching: num errors are allowed in the string matched
by the pattern. The rules for this are described in the next
subsection.
- s, e
- Unlike the other flags, these have only a local effect, and each must
appear on its own: ` (#s)' and `(#e)' are the only valid
forms. The ` (#s)' flag succeeds only at the start of the test
string, and the ` (#e)' flag succeeds only at the end of the test
string; they correspond to ` ^' and `$' in standard regular
expressions. They are useful for matching path segments in patterns other
than those in filename generation (where path segments are in any case
treated separately). For example, ` *((#s)|/)test((#e)|/)*' matches
a path segment ` test' in any of the following strings:
test, test/at/start, at/end/test,
in/test/middle.
Another use is in parameter substitution; for example `
${array/(#s)A*Z(#e)}' will remove only elements of an array which match
the complete pattern `
A*Z'. There are other ways of performing many
operations of this type, however the combination of the substitution
operations `
/' and `
//' with the `
(#s)' and
`
(#e)' flags provides a single simple and memorable method.
Note that assertions of the form `
(^(#s))' also work, i.e. match
anywhere except at the start of the string, although this actually means
`anything except a zero-length portion at the start of the string'; you need
to use `
(""~(#s))' to match a zero-length portion of the
string not at the start.
- q
- A `q' and everything up to the closing parenthesis of the globbing
flags are ignored by the pattern matching code. This is intended to
support the use of glob qualifiers, see below. The result is that the
pattern ` (#b)(*).c(#q.)' can be used both for globbing and for
matching against a string. In the former case, the ` (#q.)' will be
treated as a glob qualifier and the ` (#b)' will not be useful,
while in the latter case the ` (#b)' is useful for backreferences
and the ` (#q.)' will be ignored. Note that colon modifiers in the
glob qualifiers are also not applied in ordinary pattern matching.
- u
- Respect the current locale in determining the presence of multibyte
characters in a pattern, provided the shell was compiled with
MULTIBYTE_SUPPORT. This overrides the MULTIBYTE option; the
default behaviour is taken from the option. Compare U. (Mnemonic:
typically multibyte characters are from Unicode in the UTF-8 encoding,
although any extension of ASCII supported by the system library may be
used.)
- U
- All characters are considered to be a single byte long. The opposite of
u. This overrides the MULTIBYTE option.
For example, the test string
fooxx can be matched by the pattern
(#i )FOOXX, but not by
(#l)FOOXX,
(#i)FOO (#I)XX or
((#i)FOOX)X. The string
(#ia2)readme
specifies case-insensitive matching of
readme with up to two errors.
When using the ksh syntax for grouping both
KSH_GLOB and
EXTENDED_GLOB must be set and the left parenthesis should be preceded
by
@. Note also that the flags do not affect letters inside
[...
] groups, in other words
(#i)[a-z] still
matches only lowercase letters. Finally, note that when examining whole paths
case-insensitively every directory must be searched for all files which match,
so that a pattern of the form
(#i)/foo/bar/... is potentially
slow.
When matching approximately, the shell keeps a count of the errors found, which
cannot exceed the number specified in the
(#anum) flags.
Four types of error are recognised:
- 1.
- Different characters, as in fooxbar and fooybar.
- 2.
- Transposition of characters, as in banana and abnana.
- 3.
- A character missing in the target string, as with the pattern road
and target string rod.
- 4.
- An extra character appearing in the target string, as with stove
and strove.
Thus, the pattern
(#a3)abcd matches
dcba, with the errors
occurring by using the first rule twice and the second once, grouping the
string as
[d][cb][a] and
[a][bc][d].
Non-literal parts of the pattern must match exactly, including characters in
character ranges: hence
(#a1)??? matches strings of length four,
by applying rule 4 to an empty part of the pattern, but not strings of length
two, since all the
? must match. Other characters which must match
exactly are initial dots in filenames (unless the
GLOB_DOTS option is
set), and all slashes in filenames, so that
a/bc is two errors from
ab/c (the slash cannot be transposed with another character).
Similarly, errors are counted separately for non-contiguous strings in the
pattern, so that
(ab|cd)ef is two errors from
aebf.
When using exclusion via the
~ operator, approximate matching is treated
entirely separately for the excluded part and must be activated separately.
Thus,
(#a1)README~READ_ME matches
READ.ME but not
READ_ME, as the trailing
READ_ME is matched without
approximation. However,
(#a1)README~(#a1)READ_ME does not
match any pattern of the form
READ?ME as all such forms
are now excluded.
Apart from exclusions, there is only one overall error count; however, the
maximum errors allowed may be altered locally, and this can be delimited by
grouping. For example,
(#a1)cat((#a0)dog)fox allows one error in
total, which may not occur in the
dog section, and the pattern
(#a1 )cat(#a0)dog(#a1)fox is
equivalent. Note that the point at which an error is first found is the
crucial one for establishing whether to use approximation; for example,
(#a1)abc(#a0)xyz will not match
abcdxyz, because the error
occurs at the `
x', where approximation is turned off.
Entire path segments may be matched approximately, so that `
(#a1)/foo/d/is/available/at/the/bar' allows one error in any path
segment. This is much less efficient than without the
(#a1), however,
since every directory in the path must be scanned for a possible approximate
match. It is best to place the
(#a1) after any path segments which are
known to be correct.
A pathname component of the form `
(foo/)#' matches a path
consisting of zero or more directories matching the pattern
foo.
As a shorthand, `
**/' is equivalent to `
(*/)#'; note that this
therefore matches files in the current directory as well as subdirectories.
Thus:
or
does a recursive directory search for files named `
bar' (potentially
including the file `
bar' in the current directory). This form does not
follow symbolic links; the alternative form `
***/' does, but is
otherwise identical. Neither of these can be combined with other forms of
globbing within the same path segment; in that case, the `
*' operators
revert to their usual effect.
Even shorter forms are available when the option
GLOB_STAR_SHORT is set.
In that case if no
/ immediately follows a
** or
*** they
are treated as if both a
/ plus a further
* are present. Hence:
setopt GLOBSTARSHORT
ls **.c
is equivalent to
Patterns used for filename generation may end in a list of qualifiers enclosed
in parentheses. The qualifiers specify which filenames that otherwise match
the given pattern will be inserted in the argument list.
If the option
BARE_GLOB_QUAL is set, then a trailing set of parentheses
containing no `
|' or `
(' characters (or `
~' if it is
special) is taken as a set of glob qualifiers. A glob subexpression that would
normally be taken as glob qualifiers, for example `
(^x)', can be
forced to be treated as part of the glob pattern by doubling the parentheses,
in this case producing `
((^x))'.
If the option
EXTENDED_GLOB is set, a different syntax for glob
qualifiers is available, namely `
(#qx)' where
x
is any of the same glob qualifiers used in the other format. The qualifiers
must still appear at the end of the pattern. However, with this syntax
multiple glob qualifiers may be chained together. They are treated as a
logical AND of the individual sets of flags. Also, as the syntax is
unambiguous, the expression will be treated as glob qualifiers just as long
any parentheses contained within it are balanced; appearance of `
|',
`
(' or `
~' does not negate the effect. Note that qualifiers
will be recognised in this form even if a bare glob qualifier exists at the
end of the pattern, for example `
*(#q*)(.)' will recognise executable
regular files if both options are set; however, mixed syntax should probably
be avoided for the sake of clarity. Note that within conditions using the `
[[' form the presence of a parenthesised expression
(#q... ) at the end of a string indicates that globbing
should be performed; the expression may include glob qualifiers, but it is
also valid if it is simply
(#q). This does not apply to the right hand
side of pattern match operators as the syntax already has special
significance.
A qualifier may be any one of the following:
- /
- directories
- F
- `full' (i.e. non-empty) directories. Note that the opposite sense
(^F ) expands to empty directories and all non-directories.
Use (/^F) for empty directories.
- .
- plain files
- @
- symbolic links
- =
- sockets
- p
- named pipes (FIFOs)
- *
- executable plain files (0100 or 0010 or 0001)
- %
- device files (character or block special)
- %b
- block special files
- %c
- character special files
- r
- owner-readable files (0400)
- w
- owner-writable files (0200)
- x
- owner-executable files (0100)
- A
- group-readable files (0040)
- I
- group-writable files (0020)
- E
- group-executable files (0010)
- R
- world-readable files (0004)
- W
- world-writable files (0002)
- X
- world-executable files (0001)
- s
- setuid files (04000)
- S
- setgid files (02000)
- t
- files with the sticky bit (01000)
- fspec
- files with access rights matching spec. This spec may be a
octal number optionally preceded by a ` =', a `+', or a `
-'. If none of these characters is given, the behavior is the same
as for ` ='. The octal number describes the mode bits to be
expected, if combined with a ` =', the value given must match the
file-modes exactly, with a ` +', at least the bits in the given
number must be set in the file-modes, and with a ` -', the bits in
the number must not be set. Giving a ` ?' instead of a octal digit
anywhere in the number ensures that the corresponding bits in the
file-modes are not checked, this is only useful in combination with `
='.
If the qualifier `
f' is followed by any other character anything up to
the next matching character (`
[', `
{', and `
<' match
`
]', `
}', and `
>' respectively, any other character
matches itself) is taken as a list of comma-separated
sub-specs. Each
sub-spec may be either an octal number as described above or a list of
any of the characters `
u', `
g', `
o', and `
a',
followed by a `
=', a `
+', or a `
-', followed by a list
of any of the characters `
r', `
w', `
x', `
s', and
`
t', or an octal digit. The first list of characters specify which
access rights are to be checked. If a `
u' is given, those for the
owner of the file are used, if a `
g' is given, those of the group are
checked, a `
o' means to test those of other users, and the `
a'
says to test all three groups. The `
=', `
+', and `
-'
again says how the modes are to be checked and have the same meaning as
described for the first form above. The second list of characters finally says
which access rights are to be expected: `
r' for read access,
`
w' for write access, `
x' for the right to execute the file (or
to search a directory), `
s' for the setuid and setgid bits, and
`
t' for the sticky bit.
Thus, `
*(f70?)' gives the files for which the owner has read, write, and
execute permission, and for which other group members have no rights,
independent of the permissions for other users. The pattern `
*(f-100)'
gives all files for which the owner does not have execute permission, and `
*(f:gu+w,o-rx:)' gives the files for which the owner and the other
members of the group have at least write permission, and for which other users
don't have read or execute permission.
- estring
- +cmd
- The string will be executed as shell code. The filename will be
included in the list if and only if the code returns a zero status
(usually the status of the last command).
In the first form, the first character after the `
e' will be used as a
separator and anything up to the next matching separator will be taken as the
string; `
[', `
{', and `
<' match `
]',
`
}', and `
>', respectively, while any other character matches
itself. Note that expansions must be quoted in the
string to prevent
them from being expanded before globbing is done.
string is then
executed as shell code. The string
globqual is appended to the array
zsh_eval_context the duration of execution.
During the execution of
string the filename currently being tested is
available in the parameter
REPLY; the parameter may be altered to a
string to be inserted into the list instead of the original filename. In
addition, the parameter
reply may be set to an array or a string, which
overrides the value of
REPLY. If set to an array, the latter is
inserted into the command line word by word.
For example, suppose a directory contains a single file `
lonely'. Then
the expression `
*(e:'reply=(${REPLY}{1,2})':)' will cause the words `
lonely1' and `
lonely2' to be inserted into the command line.
Note the quoting of
string.
The form
+cmd has the same effect, but no delimiters appear around
cmd. Instead,
cmd is taken as the longest sequence of characters
following the
+ that are alphanumeric or underscore. Typically
cmd will be the name of a shell function that contains the appropriate
test. For example,
nt() { [[ $REPLY -nt $NTREF ]] }
NTREF=reffile
ls -l *(+nt)
lists all files in the directory that have been modified more recently than
reffile.
- ddev
- files on the device dev
- l[-|+]ct
- files having a link count less than ct (-), greater than
ct ( +), or equal to ct
- U
- files owned by the effective user ID
- G
- files owned by the effective group ID
- uid
- files owned by user ID id if that is a number. Otherwise, id
specifies a user name: the character after the ` u' will be taken
as a separator and the string between it and the next matching separator
will be taken as a user name. The starting separators ` [',
`{', and ` <' match the final separators ` ]',
`}', and `>', respectively; any other character matches
itself. The selected files are those owned by this user. For example, `
u:foo:' or `u[foo]' selects files owned by user `
foo'.
- gid
- like uid but with group IDs or names
- a[Mwhms][-|+]n
- files accessed exactly n days ago. Files accessed within the last
n days are selected using a negative value for n
(-n). Files accessed more than n days ago are
selected by a positive n value ( +n). Optional unit
specifiers ` M', `w', ` h', `m' or `s'
(e.g. ` ah5') cause the check to be performed with months (of 30
days), weeks, hours, minutes or seconds instead of days, respectively. An
explicit ` d' for days is also allowed.
Any fractional part of the difference between the access time and the current
part in the appropriate units is ignored in the comparison. For instance, `
echo *(ah-5)' would echo files accessed within the last five hours,
while `
echo *(ah+5)' would echo files accessed at least six hours ago,
as times strictly between five and six hours are treated as five hours.
- m[Mwhms][-|+]n
- like the file access qualifier, except that it uses the file modification
time.
- c[Mwhms][-|+]n
- like the file access qualifier, except that it uses the file inode change
time.
- L[+|-]n
- files less than n bytes (-), more than n bytes
(+), or exactly n bytes in length.
If this flag is directly followed by a
size specifier `
k'
(`
K'), `
m' (`
M'), or `
p' (`
P') (e.g.
`
Lk-50') the check is performed with kilobytes, megabytes, or blocks
(of 512 bytes) instead. (On some systems additional specifiers are available
for gigabytes, `
g' or `
G', and terabytes, `
t' or
`
T'.) If a size specifier is used a file is regarded as
"exactly" the size if the file size rounded up to the next unit is
equal to the test size. Hence `
*(Lm1)' matches files from 1 byte up to
1 Megabyte inclusive. Note also that the set of files "less than"
the test size only includes files that would not match the equality test;
hence `
*(Lm-1)' only matches files of zero size.
- ^
- negates all qualifiers following it
- -
- toggles between making the qualifiers work on symbolic links (the default)
and the files they point to
- M
- sets the MARK_DIRS option for the current pattern
- T
- appends a trailing qualifier mark to the filenames, analogous to the
LIST_TYPES option, for the current pattern (overrides
M)
- N
- sets the NULL_GLOB option for the current pattern
- D
- sets the GLOB_DOTS option for the current pattern
- n
- sets the NUMERIC_GLOB_SORT option for the current pattern
- Yn
- enables short-circuit mode: the pattern will expand to at most n
filenames. If more than n matches exist, only the first n
matches in directory traversal order will be considered.
Implies
oN when no
oc qualifier is used.
- oc
- specifies how the names of the files should be sorted. If c is
n they are sorted by name; if it is L they are sorted
depending on the size (length) of the files; if l they are sorted
by the number of links; if a, m, or c they are sorted
by the time of the last access, modification, or inode change
respectively; if d, files in subdirectories appear before those in
the current directory at each level of the search -- this is best combined
with other criteria, for example ` odon' to sort on names for files
within the same directory; if N, no sorting is performed. Note that
a, m, and c compare the age against the current time,
hence the first name in the list is the youngest file. Also note that the
modifiers ^ and - are used, so ` *(^-oL)' gives a
list of all files sorted by file size in descending order, following any
symbolic links. Unless oN is used, multiple order specifiers may
occur to resolve ties.
The default sorting is
n (by name) unless the
Y glob qualifier is
used, in which case it is
N (unsorted).
oe and
o+ are special cases; they are each followed by shell code,
delimited as for the
e glob qualifier and the
+ glob qualifier
respectively (see above). The code is executed for each matched file with the
parameter
REPLY set to the name of the file on entry and
globsort appended to
zsh_eval_context. The code should modify
the parameter
REPLY in some fashion. On return, the value of the
parameter is used instead of the file name as the string on which to sort.
Unlike other sort operators,
oe and
o+ may be repeated, but note
that the maximum number of sort operators of any kind that may appear in any
glob expression is 12.
- Oc
- like `o', but sorts in descending order; i.e. `*(^oc)' is
the same as ` *(Oc)' and `*(^Oc)' is the same as
`*(oc)'; ` Od' puts files in the current directory before
those in subdirectories at each level of the search.
- [beg[,end]]
- specifies which of the matched filenames should be included in the
returned list. The syntax is the same as for array subscripts. beg
and the optional end may be mathematical expressions. As in
parameter subscripting they may be negative to make them count from the
last match backward. E.g.: ` *(-OL[1,3])' gives a list of the names
of the three largest files.
- Pstring
- The string will be prepended to each glob match as a separate word.
string is delimited in the same way as arguments to the e
glob qualifier described above. The qualifier can be repeated; the words
are prepended separately so that the resulting command line contains the
words in the same order they were given in the list of glob
qualifiers.
A typical use for this is to prepend an option before all occurrences of a file
name; for example, the pattern `
*(P:-f:)' produces the command line
arguments `
-f file1 -f file2 ...'
If the modifier
^ is active, then
string will be appended instead
of prepended. Prepending and appending is done independently so both can be
used on the same glob expression; for example by writing `
*(P:foo:^P:bar:^P:baz:)' which produces the command line arguments `
foo baz file1 bar ...'
More than one of these lists can be combined, separated by commas. The whole
list matches if at least one of the sublists matches (they are `or'ed, the
qualifiers in the sublists are `and'ed). Some qualifiers, however, affect all
matches generated, independent of the sublist in which they are given. These
are the qualifiers `
M', `
T', `
N', `
D',
`
n', `
o', `
O' and the subscripts given in brackets (`
[...]').
If a `
:' appears in a qualifier list, the remainder of the expression in
parenthesis is interpreted as a modifier (see the section `Modifiers' in the
section `History Expansion'). Each modifier must be introduced by a separate `
:'. Note also that the result after modification does not have to be an
existing file. The name of any existing file can be followed by a modifier of
the form `
(:...)' even if no actual filename generation
is performed, although note that the presence of the parentheses causes the
entire expression to be subjected to any global pattern matching options such
as
NULL_GLOB. Thus:
lists all directories and symbolic links that point to directories, and
lists all broken symbolic links, and
lists all world-writable device files in the current directory, and
lists all files in the current directory that are world-writable or
world-executable, and
outputs the basename of all root-owned files beginning with the string `
foo' in
/tmp, ignoring symlinks, and
ls *.*~(lex|parse).[ch](^D^l1)
lists all files having a link count of one whose names contain a dot (but not
those starting with a dot, since
GLOB_DOTS is explicitly switched off)
except for
lex.c,
lex.h,
parse.c and
parse.h.
print b*.pro(#q:s/pro/shmo/)(#q.:s/builtin/shmiltin/)
demonstrates how colon modifiers and other qualifiers may be chained together.
The ordinary qualifier `
.' is applied first, then the colon modifiers
in order from left to right. So if
EXTENDED_GLOB is set and the base
pattern matches the regular file
builtin.pro, the shell will print `
shmiltin.shmo'.