Linux common commands tutorial and use examples

Linux command tutorials like you share common Linux commands, syntax and use cases, and will not list the options and parameters of each command in detail.

Linux Commands Tutorial

1. Linux common directory command list

linux cd command

• explain:
  switch directory

• syntax

   cd dir

• case

In the following example we will switch to the previous directory.

   cd - : switch to the previous directory

In the following example we will switch to the user root directory.

   cd (~) : switch to the user root directory

linux pwd command

• explain
  return to the current directory path

• syntax

   pwd

linux ls command

• explain
  list directories and files under dir

• syntax

   ls dir

• case

   ls -a DIR : list all directories and files, including. * files

linux mkdir command

• explain
  make directories

• syntax

   mkdir dir

• case

   mkdir -p /path/dir : create multilevel directories

linux rmdir command

• explain
  remove directories

• synax

   rmdir [-p] directory

2. Linux file operations commands

linux touch command

• explain
  change file timestamps

• syntax

   touch file

linux vim command

• explain
  open a file and enter “:wq” or “:x” to hold the file

• syntax

   vim/vi file

linux rm command

• explain
  delete files or directories

• syntax

   rm file

• bad case

   rm -rf / 
   rm -rf *
   rm -rf ~
      -r: indicates the following together; 
      -f: means no user confirmation required;

linux file command

• explain
  determine file type

• syntax

   file file

linux mv command

• explain
  move [rename] files or directories

• syntax
  mv source target

linux ln/link command

• explain
  make links

• syntax
  link source_file target_file

linux unlink command

• explain
  remove directory entries

• syntax
  unlink file

linux lsof command

• explain
  list open files

• syntax
  lsof names

3. Linux file permissions commands

linux chown command

• explain
  change file owner and group

• syntax
  chown owner[:group] file

linux chmod command

• explain
  change file modes or Access Control Lists

• syntax
  chmod mode file

• case

   chmod +x file : add execution permissions for all users to existing permissions
   chmod 777 file : give file owners read, write, and execute permissions

linux chgrp command

• explain:
  change group

• syntax:
  chgrp group file

4. Linux file content view commands

linux grep command

• explain:
  file pattern searcher

• syntax:
  grep pattern file

linux more command

• explain:
  displays text content and can be flipped down

• syntax:
  more file

linux less command

• explain:
  displays text content, can be flipped up or down

• syntax:
  less file

linux cat command

• explain:
  command line displays text content, -n: displays line number

• syntax:
  cat file

linux head command

• explain:
  display first lines of a file, -n: displays the first num lines

• syntax:
  head file

linux tail command

• explain:
  display the last part of a file, -n: displays the last num lines

• syntax:
  tail file

• case:

In the following example we will get the last 10 lines of the file file.log and the new content as they get appended to the file.

    tail -f file.log
    -f: tail to not stop when end of file is reached, but rather to wait for additional data to be appended to the input

5. Linux text processing commands

linux vim/vi command

• explain:
  text editor

• syntax:
  vim file

linux awk command

• explain:
  pattern-directed scanning and processing language

• syntax:
  awk [options] ‘pattern{ commands }’ file

linux sed command

• explain:
  stream editor

• syntax:
  sed command file

linux sort command

• explain:
  sort or merge records (lines) of text and binary files

• syntax:
  sort

linux tr command

• explain:
  convert or delete characters in a file

• syntax:

        tr [-Ccsu] string1 string2
        tr [-Ccu] -d string1

6. Linux file query related commands

linux find command

• explain:
  recursively display directories and files under a directory

• syntax:
  find path expression [action]

linux locate command

• explain:
  find eligible documents or directories in the database.

• syntax:
  locate file

linux ls|grep command

• explain:
  list the files and directories under the directory and match them through grep pattern

• syntax:
  ls dir | grep pattern

7. Linux file copy related commands

linux cp command

• explain:
  copy files

• syntax:
  cp source_file target_file

• case:
  cp -r : copy directory

linux scp command

• explain:
  remote file copy;The source and target may be specified as a local pathname, a remote host with optional path in the form [user@]host:[path], or a URI in the form scp://[user@]host[:port][/path].

• syntax:
  scp source target

linux syncs command

• explain:
  file synchronization and data transfer tools

• syntax

   rsync [OPTION]... SRC [SRC]... [USER@]HOST:DEST
   rsync [OPTION]... [USER@]HOST:SRC [DEST]

8. Command related commands

linux which command

• explain:
  find the command location in order from the directory listed in the Path environment variable, and display the name of the full path

• syntax:
  which command

linux whereis command

• explain:
  Find out the executable file, source code file and the path of manpage for a particular program.

• syntax:
  whereis command

linux man command

• explain:
  format and display the on-line manual pages

• syntax:
  man command

linux help command

• explain:
  display help information for the command

• syntax:
  help command

linux alias command

• explain:
  set the alias of the command

• syntax:
  alias [alias]=[command name]

linux sudo command

• explain:
  allow an authorized user to run a command as superuser or other user

• syntax:
  sudo commands

linux history command

• explain:
  display current user history operation commands

• syntax:
  history

9. System related commands

reboot/halt
    syntax: 
        halt [-lnqu]
        reboot [-lnq]
    explain: stopping and restarting the system

init 0-6
    syntax: init [0 - 6]
    explain: 0 is shutdown, 1 single user mode (can change root password), 2 multi-user mode (cannot use network), 3 full multi-user, 4 graphics, 5 security mode, 6 restart

shutdown
    syntax: shutdown time
    explain: close down the system at a given time

10. Process related commands

linux ps command

• explain:
  process status

• syntax:
  ps option

• case:

In the following example we will list the running system processes.

   ps -ef 
       : list current system processes

In the following example query whether the system is running the process.

   ps -ef | grep xxx
       : whether the query process is executing

linux kill command

• explain:
  terminate or signal a process

• syntax:

     kill pid
     kill -signal_number pid

• case:

    kill -9 pid : forced killing process

linux killall command

    syntax: killall procname
    explain: kill processes by name

linux top command

• explain
  display and update sorted information about processes

• syntax

   top option

11. Network/port related commands

netstat
    syntax: netstat option
    explain: show network status
    case: 
        netstat -anp | grep 80
            :view port 80 information

nc
    syntax: nc option
    explain: arbitrary TCP and UDP connections and listens

12. Disk related commands

df
    syntax: df [-b | -h | -H | -k | -m | -g | -P] [-ailn] [-t] [-T type] [file | filesystem ...]
    explain: display free disk space
    case: 
        df -h : view disk usage

du
    syntax: du [-H | -L | -P] [-a | -s | -d depth] [-c] [-h | -k | -m | -g] [-x] [-I mask] [file ...]
    explain: display disk usage statistics
    case: 
        du -sh *
            :display current directory file size

mount
    syntax: mount [option] device dir
    explain: mount file systems

umount
    syntax: umount [option] special | node
    explain: dismount a filesystem

fdisk
    syntax: fdisk [option] device
    explain: DOS partition maintenance program

13. User management related commands

su
    syntax: su user
    explain: switch user

useradd
    syntax: useradd user
    explain: add user

userdel
    syntax: userdel user
    explain: delete user

groupadd
    syntax: groupadd group
    explain: add group

groupdel
    syntax: groupdel group
    explain: delete group

passwd
    syntax: passwd [-i infosystem [-l location]] [-u authname] [user]
    explain: modify a user's password

14. Compression and decompression related commands

gzip/unzip
    syntax: 
        gzip option file
        unzip option file[.zip]
    explain: compression/decompression tool using Lempel-Ziv coding (LZ77)

zcat
    syntax: zcat file
    explain: print compressed file content

tar
    syntax: tar  [options] [patterns]
    explain: manipulate tape archives

bzip2/bunzip2/bzcat
    syntax: 
        bzip2 [ -cdfkqstvzVL123456789 ] [ filenames ...  ]
        bunzip2 [ -fkvsVL ] [ filenames ...  ]
        bzcat [ -s ] [ filenames ...  ]
    explain: a block-sorting file compressor

15. Other Common Commands

linux crontab command

• explain:
  service management

• syntax:
  crontab option

uname
    syntax: uname [-amnprsv]
    explain: print operating system name

date
    syntax: date option
    explain: display or set date and time

service
    syntax: service SERVICE start/stop/restart
    explain: service management

wc
    syntax: wc [-clmw] [file ...]
    explain: word, line, character, and byte count

source
    syntax: source filename or .filename
    explain: make the shell read into the specified shell program file and execute all statements in the file in turn

w
    syntax: w [option]
    explain: display who is logged in and what they are doing

echo
    syntax: echo [option]
    explain: write arguments to the standard output

print
    syntax: print contents
    explain: print contents

printf
    syntax: printf format [arguments ...]
    explain: format printed content
    case: 
        printf "Distance is %5d Miles\n" $d

ssh
    syntax: ssh [option] destination [command]
    explain: OpenSSH SSH client

ulimit
    syntax: ulimit [option]
    explain: view system limit
    case: 
        ulimit -a
            :view current limit
        ulimit -n 65535
            :temporary, effective immediately；modify /etc/security/limits.conf file, permanently effective modifications.

16. Special symbols

redirect

“>” symbol, left content overwrite to right file

“>>” symbol, the content on the left is appended to the end of the file on the right

    >
     :overwrite write
    >>
     :append write

pipe

    |
     : pipe