NAME

awka - AWK language to ANSI C translator and library

SYNOPSIS

awka [-c fn] [-X] [-x] [-t] [-o filename] [-a args] [-w args] [-I include-dir] [-i include-file] [-L lib-dir] [-l lib-file] [-f progname] [-d] [program] [--] [exe-args]
awka [-version] [-help]

DESCRIPTION

Awka is two products - a translator of AWK language programs to ANSI-C, and a library of essential functions against which the translated code must be linked.

The AWK language is useful for maniplation of datafiles, text retrieval and processing, and for prototyping and experimenting with algorithms. Usually AWK is implemented as an interpretive language - there are several good free interpreters available, notably gawk, mawk and 'The One True Awk' maintained by Brian Kernighan.

This manpage does not explain how AWK works - refer to the SEE ALSO section at the end of this page for references.

Awka is a new awk meaning it implements the AWK language as defined in Aho, Kernighan and Weinberger, The AWK Programming Language, Addison-Wesley Publishing 1988. Awka includes features from the Posix 1003.2 (draft 11.3) definition of the AWK language, but does not necessarily conform in entirety to Posix standards. Awka also provides a number of extensions not found in other implementations of AWK.

AWKA OPTIONS

-c fn

Instead of producing a 'main' function, awka will instead generate 'fn' as a controlling function. This is useful where the compiled C code is to be linked in with a larger application. The -c argument is not compatible with the -X and -x arguments. See the section USING awka -c below for more details on how to use this option.

-X

awka will generate C code, which will then be compiled into an executable, using the C compiler and intallation paths defined when Awka was installed. The C code will be stored in 'awka_out.c' and the executable in 'awka.out' or 'awka_out.exe'.

-x

The same as -X, except that the compiled program will also be executed using arguments following the '--' option on the command-line.

-t

To be used in conjunction with -x. The C file and the executable will be removed following execution of the program.

-o filename

To be used in conjunction with -x and -X. The generated executable will be called 'filename' rather than the default 'awka.out'.

-a args

This embeds executable command-line arguments within the translated code itself. For example, awka -X -a "-We" file.awk will create an awka.out that will already have -We in its command-line when it is run. To see what arguments have been embedded in an executable, use -showarg at runtime.

-w args

Prints various warnings to stderr, useful in debugging large, complex AWK programs. None of these are errors - all are acceptable uses of the AWK language. Depending on your programming style, however, they could be useful in narrowing down where problems may be occuring. args can contain the following characters:-

a - prints a list of all global variables.

b - warns about variables set to a value but not referenced.

c - warns about variables referenced but not set to a value.

d - reports use of global vars within a function.

e - reports use of global vars within just one function.

f - requires declaration of global variables.

g - warns about assignments used as truth expressions.

NOTE: As at version 0.5.8 only a, b and c are implemented.

-I include-dir

Specifies a directory in which include files required by awka, or defined by the user, reside. You may use as many -I options as you like.

-i include-file

Specifies an include filename to be inserted in the translated code.

-L lib-dir

Specifies a directory containing libraries that may be required by awka, or defined for linking by the user. See the awka-elm manpage for more details.

-l lib-file

Specifies a library file to be linked to the translated code generated by awka at compile time (this only really makes sense if using awka -x). The lib-file is specified in the same way as C compilers, that is, the library libmystuff.a would be referred to as "-l mystuff".

Again, see the awka-elm manpage for details on awka extension libraries. Like the three previous options, you can use this as often as you like on a commandline.

-f progname

Specifies the name of an AWK language program to be translated to C. Multiple -f arguments may be specified.

program

An AWK language program on the command-line, usually surrounded by single quotes (').

--

All arguments following this will be passed to the compiled executable when it is executed. This argument only makes sense when -x has been specified.

exe-args

Arguments to be passed directly to the executable when it is run.

-h

Prints a short summary of command-line options.

-v

Prints version information then quits.

EXECUTABLE OPTIONS

An executable formed by compiling Awka-generated code against libawka.a will also understand several command-line arguments.

-help

Prints a short summary of executable command-line options, then exits.

-We

Following command-line arguments will be stored in the ARGV array, and not parsed as options.

-Wi

Sets unbuffered writes to stdout and line buffered reads from stdin.

-v var=value

Sets variable 'var' to 'value'. 'var' must be a defined scalar variable within the original AWK program else an error message will be generated.

-F value

Sets FS to value.

-showarg

Displays any embedded command-line arguments, then exits.

-awkaversion

Shows which version of awka generated the .c code for the executable.

ADDITIONAL FEATURES

awka contains a number of builtin functions may or may not presently be found in standard AWK implementations. The functions have been added to extend functionality, or to provide a faster method of performing tasks that AWK could otherwise undertake in an inefficient way.

The new functions are:-

totitle(s)

converts a string to Title or Proper case, with the first letter of each word uppercased, the remainder lowercased.

abort()

Exits the AWK program immediately without running the END section. Originally from TAWK, Gawk now supports abort() as well.

alength(a)

returns the number of elements stored in array variable a.

asort(src [,dest])

The function introduced in Gawk 3.1.0. From Gawk's manpage, this "returns the number of elements in the source array src. The contents of src are sorted using awka's normal rules for comparing values, and the indexes of the sorted values of src are replaced with sequential integers starting with 1. If the optional destination array dest is specified, then src is first duplicated into dest, and then dest is sorted, leaving the indexes of the source array src unchanged."

ascii(s,n)

Returns the ascii value of character n in string s. If n is omitted, the value of the first character will be returned. If n is longer than the string, the last character will be returned. A Null string will result in a return value of zero.

char(n)

Returns the character associated with the ascii value of n. In effect, this is the complement of the ascii function above.

left(s,n)

Returns the leftmost n characters of string s. This is more efficient than a call to substr.

right(s,n)

Returns the rightmost n characters of string s.

ltrim(s, c)

Returns a string with the preceding characters in c removed from the left of s. For instance, ltrim(" hello", "h ") will return "ello". If c is not specified, whitespace will be trimmed.

rtrim(s, c)

Returns a string with the preceding characters in c removed from the right of s. For instance, ltrim(" hello", "ol") will return " he". If c is not specified, whitespace will be trimmed.

trim(s, c)

Returns a string with the preceding characters in c removed from each end of s. For instance, trim(" hello", "oh ") will return "ell". If c is not specified, whitespace will be trimmed. The three trim functions are considerably more efficient than calls to sub or gsub.

min(x1,x2,...,xn)

Returns the lowest number in the series x1 to xn. A minimum of two and a maximum of 255 numbers may be passed as arguments to Min.

max(x1,x2,...,xn)

Returns the highest number in the series x1 to xn. A minimum of two and a maximum of 255 numbers may be passed as arguments to Max.

time(year,mon,day,hour,sec) time()

returns a number representing the date & time in seconds since the Epoch, 00:00:00GMT 1 Jan 1970. The arguments allow specification of a date/time, while no arguments will return the current time.

systime()

returns a number representing the current date & time in seconds since the Epoch, 00:00:00 GMT 1 Jan 1970. This function was included to increase compatibility with Gawk.

strftime(format, n)

returns a string containing the time indicated by n formatted according to format. See strftime(3) for more details on format specification. This function was included to increase compatibility with Gawk.

gmtime(n) gmtime()

returns a string containing Greenwich Mean Time, in the form:-

Fri Jan 8 01:23:56 1999

n is a number specifying seconds since 1 Jan 1970, while a call with no arguments will return a string containing the current time.

localtime(n) localtime()

returns a string containing the date & time adjusted for the local timezone, including daylight savings. Output format & arguments are the same as gmtime.

mktime(str)

The same as mktime() introduced in Gawk 3.1.0. See Gawk's manpage for a detailed description of what this function does.

and(y,x)

Returns the output of 'y & x'.

or(y,x)

Returns the output of 'y | x'.

xor(y,x)

Returns the output of 'y ^ x'.

compl(y)

Returns the output of '~y'.

lshift(y,x)

Returns the output of 'y << x'.

rshift(y,x)

Returns the output of 'y >> x'.

argcount()

When called from within a function, returns the number of arguments that were passed to that function.

argval(n[, arg, arg...])

When called from within a function, returns the value of variable n in the argument list. The optional arg parameters are index elements used if variable n is an array. You may not specify values for n that are larger than argcount().

getawkvar(name[, arg, arg...])

Returns the value of global variable "name". The optional arg parameters work in the same as for argval. The variable specified by name must actually exist.

gensub(r,s,f[,v])

Implementation of Gawk's gensub function. It should perform exactly the same as it does in Gawk. See Gawk's documentation for details on how to use gensub.

The SORTTYPE variable controls if and how arrays are sorted when accessed using 'for (i in j)'. The value of this variable is a bitmask, which may be set to a combination of the following values:-

  0  No Sorting
1  Alphabetical Sorting
2  Numeric Sorting
4  Reverse Order

A value for SORTTYPE of 5, therefore, indicates that the array is to be sorted Alphabetically, in Reverse order.

Awka also supports the FIELDWIDTHS variable, which works exactly as it does in Gawk.

If the FIELDWIDTHS variable is set to a space separated list of positive numbers, each field is expected to have fixed width, and awka will split up the record using the widths specified in FIELDWIDTHS. The value of FS is ignored. Assigning a value to FS overrides the use of FIELDWIDTHS, and restores the default behaviour.

Awka also introduces the SAVEWIDTHS variable. This applies when FIELDWIDTHS is in use, and $0 is being rebuilt following a change to a $1..$n field variable.

If the SAVEWIDTHS variable is set to a space separated list of positive numbers, each output field will be given a fixed width to match these numbers. $n values shorter than their specified width will be padded with spaces; if they are longer than their specified width they will be truncated. Additional values to those specified in SAVEWIDTHS will be separated using OFS.

Awka 0.7.5 supports the inet/coprocessing features introduced in Gawk 3.1.0. See the documentation accompanying the Gawk source, or visit http://home.vr-web.de/Juergen.Kahrs/gawk/gawkinet.html for details on how these work.

EXAMPLES

The command-line arguments above provide a range of ways in which awka may be used, from output of C code to stdout, through to an automatic translation compile and execution of the AWK program.

(a) Producing C code:-

  1. awka -f myprog.awk >myprog.c
2. awka -c main_one -f myprog.awk -f other.awk >myprog.c

(b) Producing C code and an executable:-

  awka -X -f myprog.awk -f other.awk

(c) Producing the C and Executable, run the executable:-

  awka -x -f myprog.awk -f other.awk -- input.txt

Afterwards, you could run the executable directly, as in:-

  awka.out input.txt

Running the same program using an interpreter such as mawk would be done as follows:-

  mawk -f myprog.awk -f other.awk input.txt

The following will run the program, passing it -v on the command-line without it being interpreted as an 'option':-

  awka.out -We -v input.txt, OR
awka -x -f myprog.awk -- -We -v input.txt

(d) Producing and running the executable, ensuring it
and the C program file are automatically removed:-

  awka -x -t -f myprog.awk -f other.awk -- input.txt

(e) A simplistic example of how awka might be used in a Makefile:-

  myprog:  myprog.o


       gcc myprog.o -lawka -lm -o myprog
myprog.o:  myprog.c
myprog.c:  myprog.awk


       awka -f myprog.awk >myprog.c

LINKING AWKA-GENERATED CODE

The C programs produced by awka call many functions in libawka.a. This library needs to be linked with your program for a workable executable to be produced.

Note that when using the -x and -X arguments this is automatically taken care of for you, so linking is only an issue when you use Awka to produce C code, which you then compile yourself. Many people many only wish to use Awka in this way, and never use awka-generated code as part of larger applications. If this is you, you needn't worry too much about this section.

As well as linking to libawka.a, your program will also need to be linked to your system's math library, typically libm.a or libm.so.

Typical compiler commands to link an awka executable might be as follows:-

gcc myprog.c -L/usr/local/lib -I/usr/local/include -lawka -lm -o myprog

OR

awka -c my_main -f myprog.awk >myprog.c
gcc -c myprog.c -I/usr/local/include -o myprog.o
gcc -c other.c -o other.o
gcc myprog.o other.o -L/usr/local/lib -lawka -lm -o myapp

If you are not sure of how your compiler works you should consult the manpage for the compiler. In release 0.7.5 Awka introduced Gawk-3.1.0's inet and coprocess features. On some platforms this may require you to link to the socket and nsl libraries (-lsocket -lnsl). To check this, look at config.h after running the configure script. The #define awka_SOCKET_LIBS indicate what, if any, extra libraries are required on your system.

USING awka -c

The -c option, as described previously, replaces the main() function with a function name of your choosing. You may then link this code to other C or C++ code, and thus add AWK functionality to a larger application.

The command line "awka -c matrix 'BEGIN { print "what is the matrix?" }'" will produce in its output the function "int matrix(int argc, char *argv[])". Obviously, this replaces the main() function, and the argc and argv variables are used the same way - they handle what awka thinks are command-line arguments. Hence argv is an array of pointers to char *'s, and argc is the number of elements in this array. argv[0], from the command-line, holds the name of the running program. You can populate as many argv[] elements as you like to pass as input to your AWK program. Just remember this array is managed by your calling function, not by awka.

That's just about it. You should be able to call your awka function (eg matrix()) as many times as you like. It will grab a little bit of memory for itself, but you should see no growing memory use with each call, as I've taken quite some time to eliminate any potential memory leaks from awka code.

Oh, one more thing, exit and abort statements in your AWK program code will still exit your program altogether, so be careful of where & how you use them.

GOING FURTHER

Awka also allows you to create your own C functions and have them accessible in your AWK programs as if they were built-in to the AWK language. See the awka-elm and awka-elmref manpages for details on how this is done.

FILES

libawka.a, libawka.so, awka, libawka.h, libdfa.a, dfa.h

SEE ALSO

awk(1), mawk(1), gawk(1), awka-elm(5) awka-elmref(5), cc(1), gcc(1)

Aho, Kernighan and Weinberger, The AWK Programming Language, Addison-Wesley Publishing, 1988, (the AWK book), defines the language, opening with a tutorial and advancing to many interesting programs that delve into issues of software design and analysis relevant to programming in any language.

The GAWK Manual, The Free Software Foundation, 1991, is a tutorial and language reference that does not attempt the depth of the AWK book and assumes the reader may be a novice programmer. The section on AWK arrays is excellent. It also discusses Posix requirements for AWK.

Like you, I should probably buy & read these books some day.

MISSING FEATURES

awka does not implement gawk's internal variable IGNORECASE. Gawk's /dev/pid functions are also absent.

Nextfile and next may not be used within functions. This will never be supported, unlike the previous features, which may be added to awka over time. Well, so I thought. As of release 0.7.3 you _can_ use these from within functions.

AUTHOR

Andrew Sumner (andrewsumner@yahoo.com)

The awka homepage is at http://awka.sourceforge.net. The latest version of awka, along with development 'snapshot' releases, are available from this page. All major releases will be announced in comp.lang.awk. If you would like to be notified of new releases, please send me an email to that effect. Make sure you preface any email messages with the word "awka" in the title so I know its not spam.