# Fix "Command Not Found" in Linux

## What it means

Linux cannot find the program you tried to run.

Example:

`command: not found`

## Possible Causes

- Program is not installed
- The command name is incorrect
- The program is not in your PATH

## Fix 1 — Install the program

Example on Ubuntu:

`sudo apt install program_name`

## Fix 2 — Check spelling

Linux commands are case sensitive.

Example:

`python3 != Python3`

## Fix 3 — Check PATH

See where commands are searched:

`echo $PATH`

Find the command location:

`which command_name`

## Fix 4 — Run from current directory

If running a script in the current folder:

`./script.sh`

## Notes

- Many new users forget the "./" prefix when running local scripts.