Bash shebang option -l

Question

I use a script, test.sh, written by someone else, the begins with a bash shebang:

#!/bin/bash -l
...
echo TEST: $TEST

From what I could see, this has an effect on variables used inside the script:

• if I run TEST=hey ./test.sh, I can see TEST: hop, hop being the value of variable TEST in my .bash_profile
• this is the same if I export TEST=hey before running the script
• but if I remove the -l flag, the same command returns TEST: hey, as I would have expected

Can someone please explain this behaviour ? The help of bash did not... help.

Answer 1

The -l option (according to the man page) makes "bash act as if it had been invoked as a login shell". Login shells read certain initialization files from your home directory, such as .bash_profile. Since you set the value of TEST in your .bash_profile, the value you set on the command line gets overridden when bash launches.