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In programming, a shebang is a series of tags and exclamation marks #!at the beginning of a file. It then provides the entire path to the interpreter that will execute the file's code /bin/bash.

After that, comes the code itself. The interpreter usually ignores the shebang line, because #the character is a comment marker in many scripting languages.

Shebang Syntax

The shebang interpreter directive takes the following form.

#!interpreter [optional-arg]

In most cases, the interpreter is the only absolute path to a program that can be run.

An optional parameter is a single argument represented by a string. #!No space is required after it.

The file can be executed in Linux under the following conditions.

• The interpreter's files have execute permissions and contain code that the kernel can directly execute.
• This file defines a sysctlwrapper that wineexecutes any .exefile for example using .
• The file contains a shebang.

Interpreters on Linux can also be scripts. A chain of shebangs and wrappers produces a direct executable file that reverses the order of the script as input.

Shebang Examples

Below are some examples of typical shebang lines.

#!/bin/sh

Use the Bourne shell or other compatible shell to run this file, which is assumed to be located /binin the directory.

#!/bin/bash

Run the file using a Bash shell.

#!/usr/bin/pwsh

Run the file using PowerShell.

#!/usr/bin/env python3

Run it using the Python interpreter, and use envthe program search path to find it.

#!/bin/false

It returns a non-zero exit status indicating failure rather than doing nothing. It is used to prevent script files designed for use in a specific context (for example sh/bash) from running standalone.

The purpose of the community

The interpreter directive allows scripts and data files to be used as commands, obscuring the complexity of the implementation from users and other programs, by eliminating the need to precede the script with its interpreter on the command line.

some/path/to/fooThe first line of the Bourne shell script identified by path is as follows.

#!/bin/sh -x

It is run with arguments barand baz.

some/path/to/foo bar baz

It produces the same results as the following command line.

/bin/sh -x some/path/to/foo bar baz

If the Bourne shell is /bin/shspecified by , then some/path/to/fooall shell commands in the file are run using $1the values ​​of the positional variables barand , bazrespectively $2.

The interpreter also ignores the entire shebang line because the initial number sign starts a comment in the Bourne shell language and many other languages ​​understood by the interpreter.

The interpreter decides whether to ignore shebang lines.