Bash shebang option -l

bash shell shebang
Emmanuel picture Emmanuel · Dec 10, 2013 · Viewed 12.1k times · Source

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

dg99 picture dg99 · Dec 10, 2013

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.

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