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Ashish Kumar Thakur
Asked: 2018-05-19 02:44:03 +0800 CST

What is the shebang ( #!/bin/bash). [duplicate]

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why do we use shebang in the beginning of a shell script file. does the script will run without it.

I tried running it without shebang in shell script but it didn't run.

scripts command-line shebang

2 Answers

  1. When a file script starts with the shebang directive

    #!langpath args

    and has execution permissions set, Unix will "replace it" by

    exec langpath args path-to-the-script.

    This ways, typically:

    • langpath defines the language to be used, ans should be the path of an executable interpreter of the (programming) language (ex: '/usr/bin/python')
    • the language should accept a script file as an argument
    • the language should ignore the #!... directive as a comment
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  2. Different shells support different features. To give effective advice, ShellCheck needs to know which shell your script is going to run on. You will get a different numbers of warnings about different things depending on your target shell.

    ShellCheck normally determines your target shell from the shebang (having e.g. #!/bin/sh as the first line). The shell can also be specified from the CLI with -s, e.g. shellcheck -s sh file.

    If you don't specify shebang nor -s, ShellCheck gives this message and proceeds with some default (bash).

    Note that this error can not be ignored with a directive. It is not a suggestion to improve your script, but a warning that ShellCheck lacks information it needs to be helpful.

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