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Linux Commands with Examples

Before learning the Linux commands, its suggested to have some basic understanding of Linux -

  • Linux is not O.S, it is actually a Kernel
  • Flavour of Linux are RedHat, Fedora, OpenSue etc
  • Linux kernel is free to use and modify
  • Latest version of Linux kernel is 5.x

There are various commands used in Linux, but here is a list of commonly used -

Commands for File operations

1. ls - Directory listing
Linux command for Directory Listing

2. ls -al - Formatted listing with hidden files
Linux command to list hidden files

3. ls -lt - Sorting the Formatted listing by time modification
Linux command to list files by their modification time

4. cd dir - Change directory to dir
Linux command to change directory/folder

5. cd - Change to home directory
Linux command to go to home directory

6. pwd - Show current working directory
Linux command to know current directory/folder

7. mkdir - dir Creating a directory dir
Linux command to create new directory or folder

8. cat >file - Places the standard input into the file
Linux command to to send standard input to file

9. more file - Output the contents of the file
more command in Linux

10. head file - Output the first 10 lines of the file
linux command to get first 10 lines of any file

11. tail file - Output the last 10 lines of the file
linux command to get last 10 lines of any file

12. tail -f file - Output the contents of file as it grows,starting with the last 10 lines

13. touch file - Create or update file

14. rm file - Deleting the file

15. rm -r dir - Deleting the directory

16. rm -f file - Force to remove the file

17. rm -rf dir - Force to remove the directory dir

18. cp file1 file2 - Copy the contents of file1 to file2

19. cp -r dir1 dir2 - Copy dir1 to dir2;create dir2 if not present

20. mv file1 file2 - Rename or move file1 to file2,if file2 is an existing directory

21. ln -s file - link Create symbolic link link to file

Commands for Process management

1. ps - To display the currently working processes

2. top - Display all running process

3. kill pid - Kill the process with given pid

4. killall proc - Kill all the process named proc

5. pkill pattern - Will kill all processes matching the pattern

6. bg - List stopped or background jobs,resume a stopped job in the background

7. fg - Brings the most recent job to foreground

8. fg n - Brings job n to the foreground

Commands for File permission

1. chmod octal file - Change the permission of file to octal
which can be found separately for user,group,world by adding -

  • 4-read(r)
  • 2-write(w)
  • 1-execute(x)

Commands for Searching

1. grep pattern file - Search for pattern in file

2. grep -r pattern dir - Search recursively for pattern in dir

3. command | grep pattern Search pattern in the output of a command

4. locate file - Find all instances of file

5. find . -name - filename Searches in the current directory (represented by a period) and below it, for files and directories with names starting with filename

6. pgrep pattern - Searches for all the named processes
that matches with the pattern and, by default, returns their ID

Commands for System Info

1. date - Show the current date and time

2. cal - Show this month's calender

3. uptime -0 Show current uptime

4. w - Display who is on line

5. whoami - Who you are logged in as

6. finger user Display information about user

7. uname -a Show kernel information

8. cat /proc/cpuinfo Cpu information

9. cat proc/meminfo - Memory information

10. man command - Show the manual for command

11. df - Show the disk usage

12. du - Show directory space usage

13. free - Show memory and swap usage

14. whereis app - Show possible locations of app

15. which app - Show which applications will be run by default

Commands for Compression

1. tar cf file.tar file - Create tar named file.tar containing file

2. tar xf file.tar - Extract the files from file.tar

3. tar czf file.tar.gz files - Create a tar with Gzip compression

4. tar xzf file.tar.gz - Extract a tar using Gzip

5. tar cjf file.tar.bz2 - Create tar with Bzip2 compression

6. tar xjf file.tar.bz2 - Extract a tar using Bzip2

7. gzip file - Compresses file and renames it to file.gz

8. gzip -d file.gz - Decompresses file.gz back to file

Commands for Networking

1. ping host - Ping host and output results

2. whois domain - Get whois information for domains

3. dig domain - Get DNS information for domain

4. dig -x host - Reverse lookup host

5. wget file - Download file

6. wget -c file - Continue a stopped download

Shortcuts Commands used in Linux

1. ctrl+c - Halts the current command

2. ctrl+z - Stops the current command, resume with fg in the foreground or bg in the background

3. ctrl+d - Logout the current session, similar to exit

4. ctrl+w - Erases one word in the current line

5. ctrl+u - Erases the whole line

6. ctrl+r - Type to bring up a recent command

7. !! - Repeats the last command

8. exit - Logout the current session