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awk

Specify other flags in awk script header

I want to write an awk script file using the #!/bin/awk -f header, but I want this script to always use : as a field separator. But for some reason writing #!/bin.awk -F: -f gives me a syntax error. I also want this script to always run on the same file, so I'd like to hardcode that as well. Basically, what I want to work is this:

#!/bin/awk -F: -f -- /etc/passwd

followed by some awk code

Solution

  • Many systems allow only a single argument in a shebang line, so everything after the space is passed as one argument.

    However, you can set FS and even ARGV in your script's BEGIN block, like this:

    #!/bin/awk -f              # using the #!/bin/awk -f
BEGIN {
    FS=":"                 # always use : as a field separator
    ARGC=2
    ARGV[1]="/etc/passwd"  # always run on the same file
}
$3==0 {                    # followed by some awk code
    print $1
}

    Run it:

    $ chmod u+x program.awk
$ ./program.awk
root