The Uncarved Block

Shell Functions that are also executables

Sometimes its handy to have shell functions that can be sourced, but can also be executables in their own right. Here's how.

Sometimes it's useful to have shell functions that can be used both from within my current shell and sourced inside scripts which I write. To achieve this is fairly easy if you arrange things according to a simple convention. What I do is to make a directory called "lib" in my homedir, and put each function into a seperate file in there that has the same name as the function.

For example, I wrote a small function to print the name of the file in a given directory that has most recently been modified. To make this more generic, I got it to print the n-th from last, rather than specifically the last. So I make a small file called ~/lib/printlastfile containing the following:

# vim: set syn=zsh:

#if no args are supplied, print the last filename from $TMP
#if one arg, print the n-th from last filename from $TMP
#if two args, the second arg is the name of a dir to use instead of TMP
    #expand $TMPDIR and append a trailing slash if it doesn't have one
    DIR=$( echo ${2:-${TMPDIR:-'/tmp/'}} | sed 's,[^/]$,&/,' )

    ls -t "${DIR}"* | sed -n "${RANK}p;${RANK}q"

So any time I want that function I can just source that file. Now say I want an executable that runs printlastfile. I could make ~/bin/printlastfile as follows:

. ~/lib/printlastfile
printlastfile "${1}" "${2}"

... but that gets a bit tedious when you have a few of these things so I made one generic executable that for any function, will source the function and then run it. I call it libsquiggle because it turns things which are in squiggle/lib into executables and it looks like this:

#!/usr/bin/env zsh

. "${HOME}/lib/${MYNAME}"

$MYNAME "$@"

So I make an executable called libsquiggle that looks like that and for any function in ~/lib that I want to work as an executable I make a symlink in ~/bin called the name of the function and pointing to ~/bin/libsquiggle. Thus:

ls -l =printlastfile

lrwxrwxrwx  1 sean sean 11 Oct  5  2005 /home/huntse/bin/printlastfile -> libsquiggle

permalink Updated: 2006-04-30