sobota, 13 lutego 2016

bash: $0 value

When a script is run from a command line then the 0th parameter is the script's name. However, when a script is run via source command, then the 0th parameter is a shell name. Weird, but true.


$ cat test.sh 
echo "\$0 is $0"

$ bash test.sh
$0 is test.sh

$ source ./test.sh
$0 is bash
o

3 komentarze:

  1. Unknown16 lutego 2016 16:30

    When sourcing, the $0 becomes current directory + "bash". In total, this is even stranger in total:

    $ cat script.sh
    #! /bin/bash
    readlink -f $0

    $ ./script.sh
    /tmp/script.sh

    $ source ./script.sh
    /tmp/bash

    $ stat /tmp/bash
    stat: cannot stat '/tmp/bash': No such file or directory

    $ cd /proc/
    $ source /tmp/script.sh
    /proc/bash

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  2. Wojciech Muła18 lutego 2016 07:45

    Thanks for the comment. It is bizarre. :) I really hate such quirks, one has to become an expert in order to write reliable scripts.

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  3. Kondziu14 marca 2016 16:51

    I don't think source should be interpreted as running a script, but more in-lining the script in the currently-running script. In light of that it makes sense that $0 would be bash. Also see example below:

    $ cat a.sh
    echo \$0 is $0

    $ cat b.sh
    source a.sh

    $ bash a.sh
    $0 is a.sh

    $ bash b.sh
    $0 is b.sh

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