Cheat Sheet #day70 - chmod

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.

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