Question

I have noticed some weird behavior when sourcing another script within my shell script. The script that I am sourcing to setup the environment in my shell script takes an optional argument, e.g.

source setup.sh version1

However in my shell script I have also have command line argument variables. For example:

./myscript.sh TEST 1

Inside myscript.sh:

#!/bin/zsh
source setup.sh
echo ROOT version setup $ROOT_SYS
...more of the script

The problem that I have noticed with my script above is that the $1 argument (TEST in this example) is used in the source setup.sh command. This causes the command to become

source setup.sh TEST

which of course fails as setup.sh does not have a version TEST.

I solved this problem by editing my script to below.

#!/bin/zsh
source setup.sh version1
echo ROOT version setup $ROOT_SYS
...more of the script

The source command now does not pick up the $1 argument.

Why/How does the source command pick up the $1 argument when I am running my shell script?

Answer 1

This is because source executes the code of setup.sh as if it was in place, so when setup.sh access, say, $1, the value it has is that of the first argument of the actual script. If you want to avoid that you could either execute it:

setup.sh

or, if you need to get back some variables or values from it, change it to return the result in form of an output, something like:

ROOT_SYS=`setup.sh`

Finally, as you figured out, the source keywords also allows providing arguments to the scripts, but it bypasses current arguments if you don’t provide any.