Shebang: Difference between revisions
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=Overview= | =Overview= | ||
The <code>#!</code> sequence of characters at the beginning of a file indicates that the file is a script: a set of commands to be fed into an interpreter. The path that follows <code>#!</code> is the path to the program that interprets the commands in the script, whether it be a shell, a programming language, or a utility. The interpreter executes the commands in the script, starting with the line following the <code>#!</code> line: | The <code>#!</code> sequence of characters at the beginning of a file indicates that the file is a script: a set of commands to be fed into an interpreter. The #! is actually a two-byte magic number, a special marker that designates a file type, or in this case an executable script. The path that follows <code>#!</code> is the path to the program that interprets the commands in the script, whether it be a shell, a programming language, or a utility. The interpreter executes the commands in the script, starting with the line following the <code>#!</code> line: | ||
<syntaxhighlight lang='text'> | <syntaxhighlight lang='text'> | ||
#! <interpreter> [optional-args] | #! <interpreter> [optional-args] | ||
</syntaxhighlight> | </syntaxhighlight> | ||
=The Path Must be Absolute= | =The Path Must be Absolute= | ||
The interpreter should always be specified by absolute path to ensure that the script can be executed from any directory. When it's not, it's generally a typo and shell static checkers usually warn against this syntax. | The interpreter should always be specified by absolute path to ensure that the script can be executed from any directory. When it's not, it's generally a typo and shell static checkers usually warn against this syntax. | ||
Revision as of 00:25, 2 May 2023
External
- https://en.wikipedia.org/wiki/Shebang_(Unix)#:~:text=In%20computing%2C%20a%20shebang%20is,bang%2C%20or%20hash%2Dpling.
- https://tldp.org/LDP/abs/html/sha-bang.html
Internal
Overview
The #! sequence of characters at the beginning of a file indicates that the file is a script: a set of commands to be fed into an interpreter. The #! is actually a two-byte magic number, a special marker that designates a file type, or in this case an executable script. The path that follows #! is the path to the program that interprets the commands in the script, whether it be a shell, a programming language, or a utility. The interpreter executes the commands in the script, starting with the line following the #! line:
#! <interpreter> [optional-args]
The Path Must be Absolute
The interpreter should always be specified by absolute path to ensure that the script can be executed from any directory. When it's not, it's generally a typo and shell static checkers usually warn against this syntax.
Bash
#!/usr/bin/env bash
echo "."