README.rst

gcmd

a gawk extension providing an input parser that executes a command on the current file instead of reading it directly.

Installation

To install gcmd, simply:

$ make
$ make install

Usage

Using gcmd is simple. In your gawk script, you'll need to load gcmd, and then set one or two variables, depending on how complex a command you'd like to invoke.

gcmd uses two variables for control: GCMD and GCRS.

GCMD provides the commandline you'd like gawk to execute. The default value is "", which causes gcmd not to process anything.

GCRS provides a replacement string. When getting ready to execute the command against the current file, the value of GCRS is replaced with the current FILENAME. If the value of GCRS is not in GCMD, then FILENAME will be appended to GCMD.

A simple example:

#!/usr/bin/gawk -f
@load "gcmd"
BEGIN {
    # the resulting commandline will be "sort FILENAME"
    GCMD = "sort"
}

# write the rest of your gawk script as normal
...

It's possible to change commands between files by specifying a new value for GCMD within the BEGINFILE block:

#!/usr/bin/gawk -f
@load "gcmd"
BEGINFILE {
    GCMD = ""
    if (FILENAME == "Makefile") {
        GCMD = "make -Bnp : -f"
        RS=""
        FS="\n"
    }
}
# print a list of targets in the Makefile given
/^# Files/,/^# files hash-table/ {
    if ($1 != "# Not a target:") {
        print $1
    }
}
...

If you have a more complex commandline, making use of GCRS can be helpful:

#!/usr/bin/gawk -f
@load "gcmd"
BEGIN {
    # GCRS = "{}" by default,
    # so the resulting commandline will be "make -Bnp : -f <FILENAME> 2>/dev/null"
    GCMD = "make -Bnp : -f {} 2>/dev/null"
}
...

Notes

Some things to watch out for:

• GCMD is only processed when a file is being opened, so changing the value after gawk has started processing the file will have no effect until the next file is opened.
• Currently, gcmd cannot handle passing input from stdin to commands, so it will not even try.

Requirements

• gawk >= 4.1.0

License

BSD 3-Clause licensed. See the bundled LICENSE file for more details.