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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.
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-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.
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-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.
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-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.
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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.
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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
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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
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(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.
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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
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(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
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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.
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