How to use the shebang

What is the shebang?

A script file’s shebang, or special character sequence, indicates which program should be called in order to execute the script. The path to the interpreter program is followed by the characters #! to form the shebang, which appears on the first line of the file every time. If needed, you can additionally give options for the command line.

For example, the following line contains the shebang, the path to the Perl interpreter, and the command line option -w:

#!/usr/bin/perl -w

The shebang is especially important for CGI script files. For example, if a file named script.cgi contains the previous shebang line, you can run it from the command line by simply typing:

Copy./script.cgi

Similarly, the Apache web server services is able to run the file as a CGI script, because it knows it must call the Perl interpreter.

Many scripting languages, such as Perl, use the # character to indicate the beginning of a comment line that should be ignored by the interpreter. The shebang is a special exception to this rule.

Using the correct shebang

The following table shows the correct shebangs to use in script files that run on Hostvento Hosting web servers:

You do not need to use the shebang for PHP script files that generate web output.

There is an alternative to using absolute paths to the interpreter in shebang lines. To make your script files more portable across different systems, you can use the env program to determine the path to the interpreter. For example, consider the following shebang line:

#!/usr/bin/env ruby

This example locates and runs the Ruby interpreter, whether it is located in the /usr/bin/ directory, the /usr/local/bin/ directory, or somewhere else. You do not have to know the absolute path to the Ruby interpreter, because the env program figures it out at runtime.