After years of using AWK for programming I've found that despite of
its simplicity and limitations AWK is good enough for scripting a wide
range of different tasks. AWK is not as poweful as their bigger
counterparts like Perl, Ruby, TCL and others but it has their own
advantages like compactness, simplicity and availability on almost all
UNIX-like systems. I personally also like its data-driven nature and
token orientation, very useful technique for simple text processing
utilities.
But! Unfortunately awk interpreters lacks some important features and
sometimes work not as good as it whould be.
Problems I see (some of them, of course)
AWK lacks support for modules. Even if I create small programs, I
often want to use the functions created earlier and already used in
other scripts. That is, it whould great to orginise functions into
so called libraries (modules).
In order to pass arguments to #!/usr/bin/awk -f script (not to awk
interpreter), it is necessary to prepand a list of
arguments with -- (two minus signes). In my view, this looks badly.
Example:
awk_program:
#!/usr/bin/awk -f
BEGIN {
for (i=1; i < ARGC; ++i){
printf "ARGV [%d]=%s\n", i, ARGV [i]
}
}
When #!/usr/bin/awk -f script handles arguments (options) and wants
to read from stdin, it is necessary to add
/dev/stdin (or `-') as a last argument explicitly.
Example:
awk_program:
#!/usr/bin/awk -f
BEGIN {
if (ARGV [1] == "--flag"){
flag = 1
ARGV [1] = "" # to not read file named "--flag"
}
}
{
print "flag=" flag " $0=" $0
}
Shell session:
% echo test | awk_program -- --flag
% echo test | awk_program -- --flag /dev/stdin
flag=1 $0=test
%
Ideally awk_program should work like this
% echo test | awk_program --flag
flag=1 $0=test
%
runawk was created to solve all these problems
OPTIONS
-h|--help
Display help information.
-V|--version
Display version information.
-d|--debug
Turn on a debugging mode in which runawk prints argument list
with which real awk interpreter will be run.
-i|--with-stdin
Always add stdin file name to a list of awk arguments
-I|--without-stdin
Do not add stdin file name to a list of awk arguments
-e|--executeprogram
Specify program. If -e is not specified program is read from
program_file.
DETAILS/INTERNALS
Standalone script
Under UNIX-like OS-es you can use runawk
by beginning your script with
#!/usr/local/bin/runawk
line or something like this instead of
#!/usr/bin/awk -f
or similar.
AWK modules
In order to activate modules you should add them into awk script like this
#use "module1.awk"
#use "module2.awk"
that is the line that specifies module name is treated as a comment line
by normal AWK interpreter but is processed by runawk especially.
Note that #use should begin with column 0,
no spaces are allowed before it and no spaces are allowed between
# and use.
Also note that AWK modules can also "use" another modules and so forth.
All them are collected in a depth-first order
and each one is added to the list of
awk interpreter arguments prepanded with -f option.
That is #use directive is *NOT* similar to #include in
C programming language,
runawk's module code is not inserted into the place of #use.
Runawk's modules are closer to Perl's "use" command.
In case some module is mentioned more than once, only one -f
will be added for it, i.e duplications are removed automatically.
Position of #use directive in a source file does matter, i.e.
the earlier module is mentioned, the earlier -f will be generated for it.
Modules are first searched in a directory where main
program (or module in which #use directive is specified) is placed.
If it is not found there, then
AWKPATH environment variable is
checked. AWKPATH keeps a colon separated
list of search directories.
Finally, module is searched in system runawk modules directory,
by default PREFIX/share/runawk but this can be changed at build time.
An absolute path of the module can also be specified.
AWK interpreter and its arguments
In order to pass arguments to AWK script correctly, runawk
treats their arguments beginning with `-' sign (minus) especially.
The following command
runawk prog2 -x -f=file -o=output file1 file2
or
/path/to/prog2 -x -f=file -o=output file1 file2
will actually run
awk -f prog2 -- -x -f=file -o=output file1 file2
therefore -s, -f, -o options will be passed to ARGV/ARGC awk's variables
together with file1 and file2. If all arguments begin with `-' (minus),
runawk will add stdin filename to the end of argument list,
(unless -I option is specified) i.e. running
runawk prog3 --value=value
or
/path/to/prog3 --value=value
will actually run the following
awk -f prog3 -- --value=value /dev/stdin
Program as an argument
Like some other interpreters
runawk can obtain the script from a command line like this
For some reason you may prefer one AWK interpreter or another with a help of
#interp command like this
file prog:
#!/usr/local/bin/runawk
#use "A.awk"
#use "B.awk"
#interp "/usr/pkg/bin/nbawk"
# your code here
...
The reason may be efficiency for a particular task, useful but
not standard extensions or enything else.
Note that #interp directive should also begin with column 0,
no spaces are allowed before it and between # and interp.
Setting environment
In some cases you may want to run AWK interpreter with a
specific environment. For example, your script may be oriented to
process ASCII text only. In this case you can run AWK with LC_CTYPE=C
environment and use regexp ranges.
runawk provides #env directive for this. Strings inside double quotes
is passed to putenv(3) libc function.
Example:
file prog:
#!/usr/local/bin/runawk
#env "LC_ALL=C"
$1 ~ /^[A-Z]+$/ { # A-Z is valid if LC_CTYPE=C
print $1
}
EXIT STATUS
If AWK interpreter exits normally, runawk exits with its exit
status. If AWK interpreter was killed by signal, runawk
exits with exit status 128+signal.
ENVIRONMENT
AWKPATH
Colon separated list of directories where awk modules are searched.
RUNAWK_AWKPROG
Sets the path to the AWK interpreter, used by default,
i.e. this variable overrides the compile-time default.
Note that #interp directive overrides this.
Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:
The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.
THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
BUGS/FEEDBACK
Please send any comments, questions, bug reports etc. to me by e-mail
or (even better) register them at sourceforge project home. Feature
requests are also welcomed.
