How to create and use aliases in Bash

Repeated option-heavy commands are easy to mistype in an interactive Bash terminal, especially when the same command is run many times during one session. A Bash alias gives that command a short name for simple replacements such as a preferred ls format, while shell functions are better for shortcuts that need arguments, tests, or branching.

The alias builtin stores a name-to-command mapping in the current interactive shell. A temporary alias starts working as soon as it is defined, and unalias removes it from that shell without changing any startup file.

Persistent aliases belong in ~/.bashrc on typical Bash terminals because that file is read for interactive non-login shells. Check the file syntax, reload it with source, then verify both the stored definition and the command output before relying on the shortcut.

Steps to create and use Bash aliases:

Define a temporary alias in the current terminal.
```
$ alias ll='ls -lh'
```
Confirm the alias definition.
```
$ alias ll
alias ll='ls -lh'
```
Run the alias against a directory.
```
$ ll ~/projects/demo
total 0
-rw-r--r-- 1 operator operator 0 Jun  5 02:11 report.txt
```
Bash expands aliases in interactive shells by default. Scripts should use functions or full commands instead of depending on user aliases.
Remove the temporary alias when the shortcut is no longer needed.
```
$ unalias ll
```
Add the alias to ~/.bashrc.
```
$ nano ~/.bashrc
```
~/.bashrc
```
alias ll='ls -lh'
```
Keep interactive aliases in ~/.bashrc. Use a function instead when the shortcut needs parameters, tests, or more than one command.

Related: How to create a function in Bash
Check ~/.bashrc for Bash syntax errors.
```
$ bash -n ~/.bashrc
```
No output from bash -n means Bash parsed the file without finding a syntax error.
Reload ~/.bashrc in the current terminal.
```
$ source ~/.bashrc
```
Confirm that the persistent alias loaded.
```
$ alias ll
alias ll='ls -lh'
```

Run the alias after reloading the startup file.

$ ll ~/projects/demo
total 0
-rw-r--r-- 1 operator operator 0 Jun  5 02:11 report.txt