Self contained stream processing scripts

[Jonas Møller]

I often use AWK to extract information from, or to convert the output of 
another process to a different format.

Because of this I've often needed to either embed AWK inside a shell 
script, or write a small supplementary shell
script that calls my AWK script, for example:

> fdisk -l | awk -f my_fdisk_filter.awk

Or, when I really need it to be self-contained:
> fdisk -l | awk -f <<EOF
> long heredoc
> EOF

Embedding AWK inside shell scripts isn't optimal, as editor support for 
multiple languages inside a shell script
is poor (I suppose you could repurpose Emacs web-mode or similar tools 
for this as well.)

I came up with the following hacky solution:

> @include "shellquote"
>
> function popen(cmd,  rdir) {
>    rdir = ENVIRON["XDG_RUNTIME_DIR"]
>    if (rdir == "")
>        rdir = "/tmp" # Should be replaced with a more secure fallback.
>
>    __fifo_path = rdir"/gawk_popen."PROCINFO["pid"]".fifo"
>    system("mkfifo " shell_quote(__fifo_path))
>    system(cmd " > " shell_quote(__fifo_path) " &")
>
>    ARGV[1] = __fifo_path
>    ARGC = 2
> }
>
> END {
>    if (__fifo_path != 0)
>        system("rm " shell_quote(__fifo_path))
> }

Which can be used like this:

> @include "popen"
> BEGIN { popen("fdisk -l") }
> /do/ { print "Some processing on fdisk output" }

I really wish this was a built-in feature, because it allows for more 
self-contained AWK scripts.