Option Files

In this lesson, we’ll explore how to organize complex awk programs in separate files and invoke them with the -f option. By saving your scripts externally, you’ll improve readability, ease maintenance, and enable reuse across projects.

Running awk Programs

For quick tasks, run a one-liner directly in your shell:

$ awk 'BEGIN { print "Hello, World!" }'
Hello, World!

To separate logic from invocation, save the program in a file (e.g., hello.awk):

# hello.awk
BEGIN {
    print "Hello, World!"
}

Then execute:

$ awk -f hello.awk
Hello, World!

The single quotes are only required when passing inline scripts; they aren’t needed when awk reads from a file.

Adding a Shebang

Turn your awk file into a standalone executable by adding a shebang and setting the execute bit:

#!/usr/bin/env awk -f
BEGIN {
    print "Hello, World!"
}

$ chmod +x hello.awk
$ ./hello.awk
Hello, World!

Pure awk Script vs Bash–awk Hybrid

You have two main patterns for script-based awk:

• Uses #!/usr/bin/env awk -f
• Limited to awk’s built-in features | ./pure-hello.awk | | Bash–awk hybrid | .sh | - Shell wrapper with #!/usr/bin/env bash
• Mix pipes, globbing, and parameter expansion
• Quotes awk code to avoid shell interpolation | ./hybrid-hello.sh |

1. Pure awk script

#!/usr/bin/env awk -f
BEGIN {
    message = "Hello, World!"
    print message
}

2. Bash–awk hybrid

#!/usr/bin/env bash
awk 'BEGIN {
    message = "Hello, World!"
    print message
}'

$ chmod +x hybrid-hello.sh
$ ./hybrid-hello.sh
Hello, World!

Declaring Variables

Inside pure awk scripts, assign variables within the BEGIN block. In hybrids, you can also pass values via -v:

# hello-v1.awk
#!/usr/bin/env awk -f

BEGIN {
    msg = "Hello, World!"
    print msg
}

# hello-v2.sh
#!/usr/bin/env bash

awk -v msg="Hello, World!" 'BEGIN {
    print msg
}'

$ awk -f hello-v1.awk
Hello, World!

$ chmod +x hello-v2.sh
$ ./hello-v2.sh
Hello, World!

Field Separators

Control how awk splits input fields either in your script or via the -F option:

Both approaches produce the same output when processing an employees.txt file:

$ ./separator.sh < employees.txt
$ awk -f separator.awk  < employees.txt

Summary

• Use awk -f script.awk or add a shebang for pure awk scripts.
• Bash–awk hybrids (.sh) combine shell capabilities with awk’s text processing.
• Choose the format that maximizes clarity, maintainability, and fits your workflow.

Links and References

• GNU awk Manual
• awk One-Liners Explained
• KornShell vs Bash Scripts