Showing posts with label linux basic commands. Show all posts
Showing posts with label linux basic commands. Show all posts

Monday, November 24, 2014

Linux Basic Commands List



Basic Linux Commands

# tty Shows the current logged in terminal
# whoami shows the currently logged in user
# which "command name"  reveals where in the search path a program is located
# echo prints to the screen
# echo $PATH  dumps the current path to STDOUT
# echo $PWD     dumps ths contents of the $PWD variable
# echo $OLDPWD  dumps the most recently visited directory
# clear         clears the screen or terminal
# reset         resets the screen buffer
# history       reveals your command history
# !110  executes the 110th command in our history

Files and Directories

# ls             list the files and directories in the present working directories
# ls -ltr        sort the files in the last modification time in reverse order
# ls -a          list all the files including hidden files and directories ( all files starting with "." are hidden files)
# ls -l          long list of all files and directories where you can check the relative 
permission on each file.
# mkdir "directory name"                 Create directory
# mkdir -p /"dir1"/"dir2"/"dir3"/        Create directory including parent dir
# touch "filename"                       Create files

# cp "dir1"  /root/    copy directory or file to another location
# mv dir1  /root/      move or rename the dir or file to different location
# rm "dir name"        To remove directory
# rm -rf "dir name"    To remove a directory recursively and forcefully

For further switches to be used with any of the above commands you can check using
# man "command name"
# "command name" --help

For example:
# rm --help
# mkdir --help
# ls --help

# cd            with no options changes to the $HOME directory
# cd ~          changes to the $HOME directory
# cd /          changes to the root of the file system
# cd Desktop/   changes us to the relative directory 'Desktop'
# cd ..         changes us one-level up in the directory tree
# cd ../..      changes us two-levels up in the directory tree

User and Group related

# useradd "username"                      creates a user
# passwd "username"                       Assign password to user
# groupadd "groupname"                    creates a group
# usermod -a -G "groupname" "username"    Add existing user to group
# groupmod -A username groupname          Add existing user to group

# useradd -d "directory name" -s "shell" -g "group name" -u "UID" "username"                                 Creates user with provided details

Command chain

# head /var/log/messages      displays opening lines of text files
# head -10 /var/log/messages  displays opening 10 lines of text files
# tail /var/log/messages      displays the closing lines of text files
# tail -10 /var/log/messages  displays the closing 10 lines of text files
# wc -l /var/log/messages     counts words and optionally lines of text files