🛣 Path and Executables

The PATH environment variable controls which executables the shell finds when you type a command name.

🧭 What Is PATH?

PATH is a colon-separated list of directories where the shell looks for programs:

$ echo $PATH
/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin

When you run a command like ls, the shell checks each directory until it finds the binary.

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🕵️‍♂️ Finding Executables

Use which or command -v to locate a program:

$ which ls
/bin/ls

$ command -v python3
/usr/bin/python3

command -v is preferred because it also works with functions and aliases.

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🧱 Adding Directories to PATH

Suppose you installed a tool in ~/bin. To make it globally accessible:

Temporarily:

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

Permanently:

Edit your profile (.bashrc, .zshrc, etc.):

echo 'export PATH="$HOME/bin:$PATH"' >> ~/.bashrc
source ~/.bashrc

Always prepend new entries so they take precedence over system defaults.

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🧪 Resolving Conflicts

Multiple binaries with same name? The first match wins:

$ ls -l /usr/bin/python*
lrwxrwxrwx 1 root root 9 Apr  1 12:00 /usr/bin/python -> python3.9
-rwxr-xr-x 1 root root 5488880 Feb 10 09:00 /usr/bin/python3.9

Use full path to call specific version:

/usr/bin/python3.9 --version

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🧾 Summary

• PATH defines where the shell searches for commands.
• Add custom directories early in the PATH to override system versions.
• Use which or command -v to verify resolution order.
• Be cautious with naming conflicts between system and local binaries.

👉 Continue to: Redirections