Cheat Sheet #day70 - chmod

chmod Command Cheatsheet

The chmod command in Unix-like systems is used to change permissions (mode) of files and directories. It allows users to specify who can read, write, or execute files. Here’s a quick reference guide:

Basic Syntax

chmod [OPTIONS] MODE FILE...

Common Options

• -c, --changes: Report only when a change is made.

    chmod -c u+x file.txt
  

• -f, --silent, --quiet: Suppress most error messages.

    chmod -f 755 file.txt
  

• -v, --verbose: Output a diagnostic for every file processed.

    chmod -v g-w file.txt
  

Mode

The mode consists of three parts:

• [ugoa]: User, Group, Other, All.

• [+-=]: Add, Remove, Set exactly.

• [rwxXst]: Read, Write, eXecute, execute only if the file is a directory or already has execute permission for some user (X), Sticky bit, Setuid, Setgid.

Examples

1. Set permissions explicitly (e.g., read, write, execute for user):

    chmod u=rwx file.txt
   

2. Add permissions (e.g., add execute permission for group):

    chmod g+x file.txt
   

3. Remove permissions (e.g., remove write permission for others):

    chmod o-w file.txt
   

4. Set permissions numerically (e.g., set read, write, execute for user and read, execute for group and others):

    chmod 755 file.txt
   

5. Recursive change (e.g., change permissions for all files in a directory):

    chmod -R u+rwX directory/
   

Additional Information

• Help option:

    chmod --help
  

• View manual page for chmod:

    man chmod
  

The chmod command is essential for managing file and directory permissions in Unix-like systems, allowing users to control access to files based on user, group, and others. For more detailed options and usage scenarios, refer to the man page or use chmod --help.