Shell - Difference between \$0 and ${BASH_SOURCE[0]}

 

^{Note: For a POSIX-compliant solution, see this answer.}

${BASH_SOURCE[0]} (or, more simply, $BASH_SOURCE^[1] ) contains the (potentially relative) path of the containing script in all invocation scenarios, notably also when the script is sourced, which is not true for $0.

^{Furthermore, as Charles Duffy points out, $0 can be set to an arbitrary value by the caller.
On the flip side, $BASH_SOURCE can be empty, if no named file is involved; e.g.:
echo 'echo "[$BASH_SOURCE]"' | bash}

The following example illustrates this:

Script foo:

#!/bin/bash
echo "[$0] vs. [${BASH_SOURCE[0]}]"

---

$ bash ./foo
[./foo] vs. [./foo]

$ ./foo
[./foo] vs. [./foo]

$ . ./foo
[bash] vs. [./foo]

$0 is part of the POSIX shell specification, whereas $BASH_SOURCE, as the name suggests, is Bash-specific.

 

Copied from: https://stackoverflow.com/questions/35006457/choosing-between-0-and-bash-source