CS131 - Week 3 (Hard)

File and Directory Management

• The chown command is used to change the owner of a file or directory.
• The chgrp command is used to change the group that owns a file or directory.

User Account Management

• The useradd command is used to create a new user account.
• Linux uses groups to categorize users and manage access to system resources.
• The /etc/passwd file contains user account information for the system.

Command Functions

• The alias command creates a shortcut or alternative name for a command or sequence of commands.
• The sudo command allows authorized users to run commands with superuser privileges.

Variable Usage in Shell Scripts

• In Shell Scripts, variables are local by default and can be made global using the export command.
• Global variables in Shell Scripts can be accessed and modified from any part of the script.

Command Differences

• echo pwd`` outputs the current working directory, while echo "pwd" outputs the string "pwd".
• echo "me" outputs the string "me", pwd outputs the current working directory, echo pwd`` outputs the current working directory, and echo $HOME outputs the user's home directory.

Graphical Editor

• The default text editor for Gnome is gedit.

Regular Expressions

• The command egrep "^(0|1)+ [a-zA-Z]+$" searchfile.txt searches the file searchfile.txt for lines containing one or more occurrences of either "0" or "1" followed by a space and one or more alphabetical characters.

Group Management

• The groupadd command is used to create a new group and specify a GID (Group ID) for the group.
• The groupdel command is used to delete a group.
• On Debian or Ubuntu, the adduser command is used to add a user to a particular group.
• On CentOS or RedHat, the usermod command is used to add a user to a particular group.