unix shell scripts
A shell script is a program designed to be run by a Unix shell. Applications of shell scripts include automating tasks and batching Unix operations.
This guide will cover the basics of creating, writing, and executing shell scripts in Unix-like operating systems.
table of contents
creating a shell script file
A shell script file can be created using any text editor. A list of popular text editors can be found in the text editors guide. If you would like to create a shell script file using the command line, you can use the touch command to create an empty file. For example, to create a shell script file named my-script.sh, you would execute the following command in the terminal.
touch my-script.sh
Additional information about unix shell commands can be found in the unix commands guide.
The extension of your shell script file will vary depending on the shell you plan to execute it with and your personal preferences. Most shell scripts use the .sh extension, for example my-script.sh. If you are using the Bash shell, you can also use the .bash extension, for example my-script.bash. If you are using the Z shell, you can use the .zsh extension, for example my-script.zsh. You could also have a shell script file with no extension at all, for example my-script.
opening a shell script file
writing a shell script
shebang
The first line of any shell script file should be the shebang line. The shebang line tells the operating system which Unix shell interpreter to use to execute the script. The shebang line starts with #! followed by the path to the interpreter. For example, if you are using the Bash shell, the shebang line would look like this:
#!/bin/bash
If you are using the Z shell, the shebang line would look like this:
#!/bin/zsh
comments
Comments in a shell script start with the # symbol. Comments are ignored by the shell interpreter.
# this is a comment
pwd
variables
More information about variables is coming soon!
functions
More information about functions is coming soon!
conditionals
More information about conditionals is coming soon!
loops
More information about loops is coming soon!
command line arguments
More information about command line arguments is coming soon!
executing a shell script
More information about executing a shell script is coming soon!
updating file permissions
More information about updating file permissions is coming soon!
running a shell script
More information about running a shell script is coming soon!
adding a shell script to the $PATH
More information about adding a shell script to the $PATH is coming soon!
resources and references
GeeksForGeeks: Creating and Running bash and zsh Scripts
Baeldung: How to Use Command Line Arguments in a Bash Script