1.1.4 Executable awk Programs

Once you have learned awk, you may want to write self-contained awk scripts, using the ‘#!’ script mechanism. You can do this on many systems.(9) For example, you could update the file ‘advice’ to look like this:

#! /bin/awk -f

BEGIN { print "Don't Panic!" }

After making this file executable (with the chmod utility), simply type ‘advice’ at the shell and the system arranges to run awk(10) as if you had typed ‘awk -f advice’:

$ chmod +x advice
$ advice
-| Don't Panic!

(We assume you have the current directory in your shell’s search path variable [typically $PATH]. If not, you may need to type ‘./advice’ at the shell.)

Self-contained awk scripts are useful when you want to write a program that users can invoke without their having to know that the program is written in awk.

Advanced Notes: Portability Issues with ‘#!’

Some systems limit the length of the interpreter name to 32 characters. Often, this can be dealt with by using a symbolic link.

You should not put more than one argument on the ‘#!’ line after the path to awk. It does not work. The operating system treats the rest of the line as a single argument and passes it to awk. Doing this leads to confusing behavior—most likely a usage diagnostic of some sort from awk.

Finally, the value of ARGV[0] (see section Built-in Variables) varies depending upon your operating system. Some systems put ‘awk’ there, some put the full pathname of awk (such as ‘/bin/awk’), and some put the name of your script (‘advice’). (d.c.) Don’t rely on the value of ARGV[0] to provide your script name.