When to Use an Alias vs Script vs a New Function in Bash

When working with Bash, it's important to understand the differences between using an alias, a script, and a new function. Each has its own unique use case and can be used to accomplish different tasks.

Aliases

An alias is a way to create a shortcut for a command or series of commands. They are defined using the "alias" keyword followed by the desired shortcut and the command it should reference. For example, the following creates an alias for the "ls -la" command −

alias ll='ls -la'

This allows the user to type "ll" instead of "ls -la" to see a long list of the contents of a directory. Aliases are stored in the user's shell profile, so they will be available every time a new terminal session is started.

One use case for aliases is to create shortcuts for frequently used commands. For example, if you frequently navigate through directories, you could create an alias for the "cd" command with the directory you want to go to, like this −

alias mydocs='cd ~/Documents'

This allows you to simply type "mydocs" in the terminal instead of typing "cd ~/Documents" every time.

It's important to note that aliases are not persistent and they are only available in the current shell session. So if you close the terminal or logout, the alias will be lost.

Scripts

A script is a file that contains a series of commands to be executed in order. They are typically used to automate repetitive tasks or to execute a set of commands that are not easily accomplished with a single command or alias.

Scripts are created using a text editor and are usually saved with the ".sh" file extension. They can be executed by running the command "bash scriptname.sh" in the terminal.

For example, let's say you need to copy a set of files from one directory to another on a regular basis. Instead of manually typing the commands to copy each file, you could create a script that contains those commands and run the script whenever you need to copy the files.

#!/bin/bash
cp ~/Desktop/file1.txt ~/Documents/
cp ~/Desktop/file2.txt ~/Documents/

Scripts can also be used to automate repetitive tasks by using loops and conditional statements. This allows you to perform tasks such as renaming multiple files or creating backups of certain files or directories.

It's important to note that scripts can be invoked in many ways, and you can also make the script executable and run it directly.

Functions

A function is a block of code that can be executed multiple times with different inputs. They are defined using the "function" keyword followed by the function name and a set of commands enclosed in curly braces. Functions are typically stored in the user's shell profile and can be used just like any other command.

For example, let's say you frequently need to search for a specific file in a directory and all its subdirectories. You could create a function that takes a search term as an argument and performs the search −

function search {
   find . -name $1 -print
}

This function can be invoked by running the command "search searchterm" in the terminal.

Functions are also useful for breaking down a complex script into smaller, more manageable pieces.

It's important to note that functions are persistent and they are available in every shell session, unlike aliases.

Conclusion

In summary, when working with Bash, it's important to understand the differences between using an alias, a script, and a new function. Each has its own unique use case and can be used to accomplish different tasks.

Aliases are a way to create a shortcut for a command or series of commands and are useful for creating shortcuts for frequently used commands. Scripts are a file that contains a series of commands to be executed in order and are typically used to automate repetitive tasks or to execute a set of commands that are not easily accomplished with a single command or alias. Functions are a block of code that can be executed multiple times with different inputs, they are useful for breaking down a complex script into smaller, more manageable pieces and are persistent across shell sessions.

Choosing the right tool depends on the task at hand and your personal workflow. Understanding the strengths and limitations of each will help you make an informed decision and improve your productivity.