sort or merge records (lines) of text and binary
utility sorts text and binary files
by lines. A line is a record separated from the subsequent record by a newline
(default) or NUL ´\0´ character (-z option). A record can
contain any printable or unprintable characters. Comparisons are based on one
or more sort keys extracted from each line of input, and are performed
lexicographically, according to the current locale's collating rules and the
specified command-line options that can tune the actual sorting behavior. By
default, if keys are not given,
entire lines for comparison.
The command line options are as follows:
- Check that the single input file is sorted. If the file is not sorted,
sort produces the appropriate error
messages and exits with code 1, otherwise returns 0. If
-check=silent is specified,
sort produces no output. This is a
"silent" version of
- Merge only. The input files are assumed to be pre-sorted. If they are not
sorted the output order is undefined.
- Print the output to the output file
instead of the standard output.
- Use size for the maximum size of the
memory buffer. Size modifiers %,b,K,M,G,T,P,E,Z,Y can be used. If a memory
limit is not explicitly specified,
takes up to about 90% of available memory. If the file size is too big to
fit into the memory buffer, the temporary disk files are used to perform
- Store temporary files in the directory
dir. The default path is the value of the
TMPDIR is not defined.
- Unique keys. Suppress all lines that have a key that is equal to an
already processed one. This option, similarly to
-s, implies a stable sort. If used with
sort also checks that there are no
lines with duplicate keys.
- Stable sort. This option maintains the original record order of records
that have an equal key. This is a non-standard feature, but it is widely
accepted and used.
- Print the version and silently exits.
- Print the help text and silently exits.
The following options override the default ordering rules. When ordering options
appear independently of key field specifications, they apply globally to all
sort keys. When attached to a specific key (see
), the ordering options override all
global ordering options for the key they are attached to.
- Ignore leading blank characters when comparing lines.
- Consider only blank spaces and alphanumeric characters in
- Convert all lowercase characters to their uppercase equivalent before
comparison, that is, perform case-independent sorting.
- Sort by general numerical value. As opposed to
-n, this option handles general
floating points. It has a more permissive format than that allowed by
-n but it has a significant performance
- Sort by numerical value, but take into account the SI suffix, if present.
Sort first by numeric sign (negative, zero, or positive); then by SI
suffix (either empty, or `k' or `K', or one of `MGTPEZY', in that order);
and finally by numeric value. The SI suffix must immediately follow the
number. For example, '12345K' sorts before '1M', because M is
"larger" than K. This sort option is useful for sorting the
output of a single invocation of 'df' command with
-H options (human-readable).
- Ignore all non-printable characters.
- Sort by month abbreviations. Unknown strings are considered smaller than
the month names.
- Sort fields numerically by arithmetic value. Fields are supposed to have
optional blanks in the beginning, an optional minus sign, zero or more
digits (including decimal point and possible thousand separators).
- Sort by a random order. This is a random permutation of the inputs except
that the equal keys sort together. It is implemented by hashing the input
keys and sorting the hash values. The hash function is chosen randomly.
The hash function is randomized by
/dev/random content, or by file content
if it is specified by
Even if multiple sort fields are specified, the same random hash function
is used for all of them.
- Sort in reverse order.
- Sort version numbers. The input lines are treated as file names in form
PREFIX VERSION SUFFIX, where SUFFIX matches the regular expression
"(.([A-Za-z~][A-Za-z0-9~]*)?)*". The files are compared by their
prefixes and versions (leading zeros are ignored in version numbers, see
example below). If an input string does not match the pattern, then it is
compared using the byte compare function. All string comparisons are
performed in C locale, the locale environment setting is ignored.
- $ ls sort* | sort -V
The treatment of field separators can be altered using these options:
- Ignore leading blank space when determining the start and end of a
restricted sort key (see
-b is specified before the first
-k option, it applies globally to all
key specifications. Otherwise,
be attached independently to each field
argument of the key specifications.
- Define a restricted sort key that has the starting position
field1, and optional ending position
field2 of a key field. The
-k option may be specified multiple
times, in which case subsequent keys are compared when earlier keys
compare equal. The
-k option replaces
the obsolete options
but the old notation is also supported.
- Use char as a field separator character.
The initial char is not considered to be
part of a field when determining key offsets. Each occurrence of
char is significant (for example,
“charchar” delimits an
empty field). If
-t is not specified,
the default field separator is a sequence of blank space characters, and
consecutive blank spaces do not delimit an
empty field, however, the initial blank space
is considered part of a field when
determining key offsets. To use NUL as field separator, use
- Use NUL as record separator. By default, records in the files are supposed
to be separated by the newline characters. With this option, NUL
(´\0´) is used as a record separator character.
- Specify maximum number of files that can be opened by
sort at once. This option affects
behavior when having many input files or using temporary files. The
default value is 16.
- Use PROGRAM to compress temporary files. PROGRAM must compress standard
input to standard output, when called without arguments. When called with
-d it must decompress standard
input to standard output. If PROGRAM fails,
sort must exit with error. An example
of PROGRAM that can be used here is bzip2.
- In random sort, the file content is used as the source of the 'seed' data
for the hash function choice. Two invocations of random sort with the same
seed data will use the same hash function and will produce the same result
if the input is also identical. By default, file
/dev/random is used.
- Print some extra information about the sorting process to the standard
- Take the input file list from the file
filename. The file names must be
separated by NUL (like the output produced by the command "find ...
- Try to use radix sort, if the sort specifications allow. The radix sort
can only be used for trivial locales (C and POSIX), and it cannot be used
for numeric or month sort. Radix sort is very fast and stable.
- Use mergesort. This is a universal algorithm that can always be used, but
it is not always the fastest.
- Try to use quick sort, if the sort specifications allow. This sort
algorithm cannot be used with
- Try to use heap sort, if the sort specifications allow. This sort
algorithm cannot be used with
- Try to use file memory mapping system call. It may increase speed in some
The following operands are available:
- The pathname of a file to be sorted, merged, or checked. If no
file operands are specified, or if a
file operand is
-, the standard input is used.
A field is defined as a maximal sequence of characters other than the field
separator and record separator (newline by default). Initial blank spaces are
included in the field unless
specified; the first blank space of a sequence of blank spaces acts as the
field separator and is included in the field (unless
is specified). For example, all blank
spaces at the beginning of a line are considered to be part of the first
Fields are specified by the
command-line option. If field2
the end of the key defaults to the end of the line.
The arguments field1
have the form
m.n (m,n > 0)
can be followed by one or more of the modifiers
which correspond to the options discussed above. When
is specified it applies only to
where it is specified while the rest
of the modifiers apply to the whole key field regardless if they are specified
only with field1
or both. A
position specified by
is interpreted as the
th character from the beginning of the
th field. A missing
’, indicating the first
character of the m
th field; if the
option is in effect,
is counted from the first non-blank character
in the m
.1b refers to the first non-blank character in
refers to the
th character from the beginning of the line; if
is greater than the length of the line, the
field is taken to be empty.
th positions are always counted from the field
beginning, even if the field is shorter than the number of specified
positions. Thus, the key can really start from a position in a subsequent
position specified by
is interpreted as the
th character (including separators) from the
beginning of the m
th field. A missing
indicates the last character of the
th field; m
designates the end of a line. Thus the option
is synonymous with the obsolete option
is synonymous with
option is still supported, except for
which has no
- Locale settings to be used to determine the collation for sorting
- Locale settings to be used to case conversion and classification of
characters, that is, which characters are considered whitespaces,
- Locale settings that determine the language of output messages that
sort prints out.
- Locale settings that determine the number format used in numeric
- Locale settings that determine the month format used in month sort.
- Locale settings that override all of the above locale settings. This
environment variable can be used to set all these settings to the same
value at once.
- Used as a last resort to determine different kinds of locale-specific
behavior if neither the respective environment variable, nor
LC_ALL are set.
- Path to NLS catalogs.
- Path to the directory in which temporary files will be stored. Note that
TMPDIR may be overridden by the
- If defined
-t will not override the
locale numeric symbols, that is, thousand separators and decimal
separators. By default, if we specify
-t with the same symbol as the thousand
separator or decimal point, the symbol will be treated as the field
separator. Older behavior was less definite; the symbol was treated as
both field separator and numeric separator, simultaneously. This
environment variable enables the old behavior.
- Temporary files.
- Default seed file for the random sort.
utility shall exit with one of the
- Successfully sorted the input files or if used with
-C, the input file already met the
- On disorder (or non-uniqueness) with the
- An error occurred.
utility is compliant with the
IEEE Std 1003.1-2008
The flags [
are extensions to the POSIX specification.
All long options are extensions to the specification, some of them are provided
for compatibility with GNU versions and some of them are own extensions.
The old key notations
from older versions of
and are still
supported but their use is highly discouraged.
command first appeared in
Version 3 AT&T UNIX
This implementation of
has no limits on
input line length (other than imposed by available memory) or any restrictions
on bytes allowed within lines.
The performance depends highly on locale settings, efficient choice of sort keys
and key complexity. The fastest sort is with locale C, on whole lines, with
. In general, locale C is the
fastest, then single-byte locales follow and multi-byte locales as the slowest
but the correct collation order is always respected. As for the key
specification, the simpler to process the lines the faster the search will be.
When sorting by arithmetic value, using
results in much better performance than
so its use is encouraged whenever possible.