New post on finding if a shell script is sourced or run.

content/sourced_or_not.rst

+Finding is a script sourced or not?
+###################################
+:date: 2016-02-29
+:summary: How to find if a shell script is sourced or not.
+
+I've recently written a shell script that contained several functions and I
+wanted to support 2 usage methods. The first is quite regular, marking it as an
+executable and running it. The second is to source the script and gain the
+functions declared. The problem is not actually performing any tasks (or
+outputing anything) if the script is being sourced. It took a bit of fiddling
+but I found a short one-liner to add at the top of the script that solves this
+in a POSIX-comliant way (at least on my test machines, Debian with Bash and Dash
+and KSH on OpenBSD). Here is an example usage:
+
+.. code:: shell
+
+    #!/bin/sh -e
+    # Check if the script is being sourced or not.
+    [ "$_" != "$0" ] && expr "$-" : ".*i.*" > /dev/null && sourced=1
+
+    if [ "$sourced" ]
+    then
+        echo Sourced
+    else
+        echo Run
+    fi
+
+The solution is using 2 heuristics. If the last argument (:code:`$_`) if
+different from the command name (must be first command run, otherwise the last
+argument will be overwritten). The second is if the option flags (:code:`$-`)
+contain :code:`i` for interactive. This works when both marking the script as
+executable and passing the name as a parameter to the shell.