Shell config and aliases

Every time you open Termux, the shell reads a startup file before it gives you a prompt. Editing that file lets you set short names for long commands, change the prompt, and add your own folders to the search path. Here you edit the file and add aliases. You set the prompt and learn how the shell finds commands.

What you'll be able to do

• Find and read your shell startup file, ~/.bashrc.
• Add aliases for commands you type often.
• Change your prompt with PS1.
• Understand PATH and why the order of folders matters.
• Export environment variables and reload the file with source.

Step 1: Meet the bashrc file

The file ~/.bashrc runs each time an interactive Bash shell starts. On Termux it already exists. Read it with cat.

cat ~/.bashrc

# ~/.bashrc
export PS1='\u@\h:\w\$ '

Lines starting with # are comments. The one real line sets the prompt. Anything you add here runs on every new shell, so keep it short and correct.

Step 2: Add aliases

An alias is a short name for a longer command. This one makes ll run ls -l. Setting an alias prints nothing when it works.

alias ll='ls -l'

Run it.

ll

total 8
drwx------ 2 u0_a123 u0_a123 4096 Feb 14 10:00 backups
-rwxr-xr-x 1 u0_a123 u0_a123   41 Feb 14 10:00 hello.sh

List your aliases to check them.

alias

alias ll='ls -l'
alias ..='cd ..'

Step 3: Change your prompt with PS1

The PS1 variable holds your prompt. It understands escapes such as \u for the user, \h for the host, \w for the current folder, and \$ for the prompt symbol.

PS1='\u@\h:\w\$ '

u0_a123@localhost:~$ 

Move into another folder and the prompt follows.

cd backups

u0_a123@localhost:~/backups$ 

Step 4: Understand PATH and its order

When you type a command, the shell searches the folders listed in PATH, in order, and runs the first match. Print it to see the list.

echo $PATH

/data/data/com.termux/files/usr/bin:/data/data/com.termux/files/usr/bin/applets

Folders are separated by colons. To add your own folder, put it at the front so your version wins.

export PATH="$HOME/bin:$PATH"

echo $PATH

/data/data/com.termux/files/home/bin:/data/data/com.termux/files/usr/bin:/data/data/com.termux/files/usr/bin/applets

Step 5: Export variables and reload the file

An environment variable is a value passed to the programs you run. export makes a variable part of the environment.

export EDITOR=nano

echo $EDITOR

nano

After you edit ~/.bashrc, load it into the current shell with source. Then you do not have to open a new one.

source ~/.bashrc

Here are a few aliases that earn their place on a phone.

alias ll='ls -la'
alias ..='cd ..'
alias update='pkg update && pkg upgrade -y'
alias grep='grep --color=auto'

Add those lines to ~/.bashrc and run source ~/.bashrc once. Then they are there every time you open Termux.

Quick reference

Command	What it does
cat ~/.bashrc	Shows your shell startup file
alias name='command'	Creates a short name for a command
alias	Lists the aliases in this shell
PS1='\u@\h:\w\$ '	Sets the prompt format
echo $PATH	Prints the command search path
export PATH="$HOME/bin:$PATH"	Adds a folder to the front of the path
export NAME=value	Puts a variable into the environment
source ~/.bashrc	Reloads the startup file into this shell

Next steps

• Shell scripting basics to turn aliases into full scripts.
• Managing packages in Termux to install the tools your aliases call.
• Buried Strings to use grep in a real task.