Linux Basic Commands Cheetsheet

Basic commands for working with text:

• Ctrl + A => move cursor in the front of text
• Ctrl + E => move cursor in the end of text
• Ctrl + U => remove(crop) the word from cursor till start of the word
• Ctrl + K => remove(crop) the word from cursor till end of word
• Ctrl + Y => Paste cropped text
• Ctrl + Shift + C => Copy text to clipboard
• Ctrl + Shift + P => Paste text to clipboard
• Ctrl + C or Ctrl + Z => Stop running the command

Commands for files and folder:

• ~ : Represents users home directory. cd ~ or cd => return to users home directory.
• pwd => Represents your absolute path of current working directory.
• . => Represents current directory.
• cd => Change directory
• cd .. => Moves one directory backwards
• cd ../../ => Moves two directory backwards
• mkdir dir-name => Create new directory if does not exist.
• rmdir dir-name => Removes directory if exists
• cp file1 file2 => Copies content of file1 to file2
• mv ./file1 ../ => Move file1 from current directory to backward directory
• rm file1.txt => Remove file1.txt
• rm -r dummy => Removes recursively all files and directory from dummy directory
• ls => List all files and directories within your current working directory.
• touch file-name => Will create a file with provided file-name.

Commands for changing file/directory permissions:

when you run ls -la on terminal you might see below:

drwxrwxrwx : d => directory, r => read, w => write, x => excute, -
=> no permission.

if d is blank then, its a file (-rwxr-xr-x)
first group(drwx) - represents owner( who created the file)
second(rwx) - represents user group (user groups other than owner, who has access to file)
third(rwx) - represents others

Numerical value for permissions r, w ,x:
r - 4
w - 2
x - 1

• chmod XXX : this is used to change the permission associated with file/directory. It's called change mode.
  X denotes permission number for an group(owner, user-group, other).
  chmod 644 - will assign read write to owner and read to both user group and other group.
The default permission is 644.
permission 777 - means all users(owner, user, others) have got full permission(rwx) on file/directory.

• chown user fileName: change ownership of a file or directory
  chown user:group filename

Commands to create hard and soft links for file:

Link => A link in UNIX are pointers pointing to a file or a directory. Links allow more than one file name to refer to the same file, elsewhere.

Two ways to create symlinks:

• ln -s file1 file 2 => This will create a soft link file2 for referring file1. Soft links break if the source file(file1) is moved or moved.
• ln file 1 file 2 => This will create a hard link file2 for referring file1. Hard links work even if then source(file1) is moved.

Commands for searching/displaying text:

• grep -n “the” file1.txt => searches "the" in file1.txt with numbered line.

• cat file1.txt => Displays the content of file.

• | => Pipe is used to send the result of one command to next command after pipe to execute on it.
  cat file.txt | wc : here result of cat command is send to wc command for further processing.

• head filename => Display first 10 lines of a file.

head file1.txt => Displays first 10 lines of file1.txt

head -n5 file1.txt => Displays first 5 lines of file1.txt

• tail filename => Display last 10 lines of a file.

tail file1.txt => Displays last 10 lines of file1.txt

tail -n5 file1.txt => Displays last 5 lines of file1.txt

cat file1.txt | tail -n5 | cat -n => This displays the last 5 lines of the file1.txt numbered as 1, 2, 3, 4, 5.

• less filename => Less will open the entire file but displays the part of file in scrollable mode, user can navigate in the file. Displays the content of file page by page.

Redirection of Inputs/Outputs/Stderr:

### File Descriptor and their representations:

• stdin => 0 => Input from the console
• stdout => 1 => Output to console
• stderr => 2 => Error to console

### Redirection:

• ' > ' => output of command1 is redirected to file.txt/stdout (Output Redirection).
• ' >> ' => output of command1 is appended to file.txt/stdout (Output Redirection).
• ' < ' => command 1 reads its input from file.txt/stdin (Input Redirection).

RAM CPU and Disk Info:

• free -h => Displays available and used RAM(memory).
• cat /proc/cpuinfo => Displays information about cpu like cores etc.
• df -h => Displays information about available and used Disks. -h here is used to display the information in human readable format

Other useful Command:

• man option command => Displays manual page for a command.
• help command => Display help information related to a command.
• uname -a => Displays information about linux system on your machine.
• hostname => Display the hostname and ip for your machine in the network. hostname -I => Will Display the ip of your system in network.
• ping => To test the reachability of the system in network. ping google.com => Will ping to google.com and if that available in network it will return the data packets