2.11 Summary

• Use either ‘awk 'program' files’ or ‘awk -f program-file files’ to run awk.
• The three standard options for all versions of awk are -f, -F, and -v. gawk supplies these and many others, as well as corresponding GNU-style long options.
• Nonoption command-line arguments are usually treated as file names, unless they have the form ‘var=value’, in which case they are taken as variable assignments to be performed at that point in processing the input.
• All nonoption command-line arguments, excluding the program text, are placed in the ARGV array. Adjusting ARGC and ARGV affects how awk processes input.
• You can use a single minus sign (‘-’) to refer to standard input on the command line. gawk also lets you use the special file name /dev/stdin.
• gawk pays attention to a number of environment variables. AWKPATH, AWKLIBPATH, and POSIXLY_CORRECT are the most important ones.
• gawk’s exit status conveys information to the program that invoked it. Use the exit statement from within an awk program to set the exit status.
• gawk allows you to include other awk source files into your program using the @include statement and/or the -i and -f command-line options.
• gawk allows you to load additional functions written in C or C++ using the @load statement and/or the -l option. (This advanced feature is described later, in Writing Extensions for gawk.)