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Unix is a powerful, multi-user, multi-tasking operating system that has been the foundation for many modern operating systems, including Linux and macOS. One of the key features of Unix is its command-line interface (CLI), which allows users to interact with the system using text-based commands. In this article, we will explore various commands in Unix with examples to help you understand how to navigate, manage files, and perform system operations efficiently.
50 Commands in Unix with Examples
Unix commands are instructions given to the operating system to perform specific tasks. These commands are executed in a shell, which is a command-line interpreter that processes user input and executes commands. The most common Unix shells are the Bourne Shell (sh), the Bourne Again Shell (bash), and the C Shell (csh).
Basic Unix Commands
Let’s start with some basic commands in Unix with examples that every user should know.
1. pwd – Print Working Directory
The pwd command displays the current working directory.
Example:
$ pwd /home/user
2. ls – List Directory Contents
The ls command lists the files and directories in the current directory.
Example:
$ ls Documents Downloads Music Pictures Videos
You can also use options with ls to display more information:
ls -l: Long listing format.ls -a: Include hidden files.
Example:
$ ls -l total 4 drwxr-xr-x 2 user user 4096 Jan 1 12:34 Documents drwxr-xr-x 2 user user 4096 Jan 1 12:34 Downloads
3. cd – Change Directory
The cd command is used to change the current working directory.
Example:
$ cd Documents $ pwd /home/user/Documents
To go back to the previous directory, use cd ...
Example:
$ cd .. $ pwd /home/user
4. mkdir – Make Directory
The mkdir command creates a new directory.
Example:
$ mkdir new_folder $ ls Documents Downloads Music new_folder Pictures Videos
5. rmdir – Remove Directory
The rmdir command removes an empty directory.
Example:
$ rmdir new_folder $ ls Documents Downloads Music Pictures Videos
6. touch – Create an Empty File
The touch command creates an empty file or updates the timestamp of an existing file.
Example:
$ touch new_file.txt $ ls Documents Downloads Music new_file.txt Pictures Videos
7. rm – Remove Files or Directories
The rm command removes files or directories. Use the -r option to remove directories recursively.
Example:
$ rm new_file.txt $ ls Documents Downloads Music Pictures Videos
Example with directory:
$ rm -r new_folder
8. cp – Copy Files or Directories
The cp command copies files or directories from one location to another.
Example:
$ cp file1.txt file2.txt $ ls file1.txt file2.txt
To copy a directory, use the -r option:
Example:
$ cp -r dir1 dir2
9. mv – Move or Rename Files or Directories
The mv command moves or renames files or directories.
Example (rename):
$ mv file1.txt file3.txt $ ls file3.txt file2.txt
Example (move):
$ mv file3.txt Documents/ $ ls Documents/ file3.txt
10. cat – Concatenate and Display Files
The cat command displays the contents of a file.
Example:
$ cat file2.txt This is the content of file2.txt.
You can also concatenate multiple files:
Example:
$ cat file1.txt file2.txt > combined.txt $ cat combined.txt This is the content of file1.txt. This is the content of file2.txt.
11. more and less – View File Content Page by Page
The more and less commands allow you to view the contents of a file one page at a time.
Example with more:
$ more large_file.txt
Example with less:
$ less large_file.txt
The less command is more advanced and allows you to scroll both forward and backward.
12. head and tail – Display the Beginning or End of a File
The head command displays the first few lines of a file, while the tail command displays the last few lines.
Example with head:
$ head -n 5 file.txt
Example with tail:
$ tail -n 5 file.txt
13. grep – Search Text Using Patterns
The grep command searches for patterns within files.
Example:
$ grep "search_term" file.txt
You can also use grep with regular expressions:
Example:
$ grep "^start" file.txt
14. find – Search for Files and Directories
The find command searches for files and directories based on various criteria.
Example:
$ find /home/user -name "*.txt"
This command searches for all .txt files in the /home/user directory.
15. chmod – Change File Permissions
The chmod command changes the permissions of a file or directory.
Example:
$ chmod 755 script.sh
This command gives the owner read, write, and execute permissions, and others read and execute permissions.
16. chown – Change File Owner
The chown command changes the owner of a file or directory.
Example:
$ chown user:group file.txt
This command changes the owner of file.txt to user and the group to group.
17. ps – Display Active Processes
The ps command displays information about active processes.
Example:
$ ps aux
This command lists all running processes.
18. kill – Terminate Processes
The kill command terminates a process by its process ID (PID).
Example:
$ kill 1234
This command terminates the process with PID 1234.
19. top – Display System Activity
The top command provides a real-time view of system activity, including CPU and memory usage.
Example:
$ top
20. df – Display Disk Space Usage
The df command displays the amount of disk space used and available on file systems.
Example:
$ df -h
The -h option makes the output human-readable.
21. du – Display Directory Space Usage
The du command displays the disk usage of files and directories.
Example:
$ du -sh /home/user
The -s option summarizes the total, and the -h option makes the output human-readable.
22. tar – Archive Files
The tar command is used to create and extract archive files.
Example (create archive):
$ tar -cvf archive.tar /home/user
Example (extract archive):
$ tar -xvf archive.tar
23. gzip and gunzip – Compress and Decompress Files
The gzip command compresses files, and gunzip decompresses them.
Example (compress):
$ gzip file.txt
Example (decompress):
$ gunzip file.txt.gz
24. ssh – Secure Shell
The ssh command is used to securely connect to a remote server.
Example:
$ ssh user@remote_host
25. scp – Secure Copy
The scp command is used to securely copy files between local and remote systems.
Example:
$ scp file.txt user@remote_host:/remote/directory
26. wget – Download Files from the Web
The wget command downloads files from the web.
Example:
$ wget https://example.com/file.txt
27. curl – Transfer Data from or to a Server
The curl command is used to transfer data from or to a server.
Example:
$ curl -O https://example.com/file.txt
28. man – Display Manual Pages
The man command displays the manual pages for other commands.
Example:
$ man ls
This command displays the manual page for the ls command.
29. alias – Create Command Aliases
The alias command creates shortcuts for longer commands.
Example:
$ alias ll='ls -la' $ ll
This command creates an alias ll for ls -la.
30. history – Display Command History
The history command displays the command history.
Example:
$ history
You can also rerun a command from history using !n, where n is the command number.
Example:
$ !123
This command reruns command number 123.
Advanced Unix Commands
Now that we’ve covered the basics, let’s dive into some more advanced commands in Unix with examples.
31. awk – Pattern Scanning and Processing
The awk command is a powerful text-processing tool.
Example:
$ awk '{print $1}' file.txt
This command prints the first column of file.txt.
32. sed – Stream Editor
The sed command is used for text substitution and manipulation.
Example:
$ sed 's/old/new/' file.txt
This command replaces the first occurrence of old with new in file.txt.
33. cut – Remove Sections from Lines of Files
The cut command is used to extract specific sections from each line of a file.
Example:
$ cut -d':' -f1 /etc/passwd
This command extracts the first field (username) from the /etc/passwd file.
34. tr – Translate or Delete Characters
The tr command translates or deletes characters.
Example:
$ tr 'a-z' 'A-Z' < file.txt
This command converts all lowercase letters in file.txt to uppercase.
35. sort – Sort Lines of Text Files
The sort command sorts lines of text files.
Example:
$ sort file.txt
This command sorts the lines in file.txt alphabetically.
36. uniq – Report or Omit Repeated Lines
The uniq command filters out repeated lines in a file.
Example:
$ uniq file.txt
This command removes duplicate lines from file.txt.
37. diff – Compare Files Line by Line
The diff command compares two files line by line.
Example:
$ diff file1.txt file2.txt
This command shows the differences between file1.txt and file2.txt.
38. ln – Create Links Between Files
The ln command creates hard or symbolic links between files.
Example (hard link):
$ ln file1.txt file2.txt
Example (symbolic link):
$ ln -s file1.txt file2.txt
39. wc – Word Count
The wc command counts lines, words, and characters in a file.
Example:
$ wc file.txt
This command displays the number of lines, words, and characters in file.txt.
40. tee – Redirect Output to Multiple Files
The tee command reads from standard input and writes to standard output and files.
Example:
$ echo "Hello, World!" | tee file1.txt file2.txt
This command writes “Hello, World!” to both file1.txt and file2.txt.
41. xargs – Build and Execute Command Lines
The xargs command builds and executes command lines from standard input.
Example:
$ find . -name "*.txt" | xargs rm
This command finds all .txt files and deletes them.
42. nohup – Run Commands Immune to Hangups
The nohup command runs another command immune to hangups.
Example:
$ nohup long_running_script.sh &
This command runs long_running_script.sh in the background, even if the terminal is closed.
43. cron – Schedule Commands
The cron command schedules commands to run at specific times.
Example:
$ crontab -e
This command opens the cron table for editing. You can add a line like this to schedule a script:
0 2 * * * /path/to/script.sh
This command runs script.sh at 2:00 AM every day.
44. at – Schedule a Command to Run Once
The at command schedules a command to run once at a specific time.
Example:
$ at 2:00 PM at> /path/to/script.sh at>
This command schedules script.sh to run at 2:00 PM.
45. watch – Execute a Command Periodically
The watch command executes a command repeatedly and displays the output.
Example:
$ watch -n 1 'date'
This command displays the current date and time every second.
46. netstat – Network Statistics
The netstat command displays network connections, routing tables, and interface statistics.
Example:
$ netstat -tuln
This command lists all listening ports.
47. ifconfig – Configure Network Interfaces
The ifconfig command configures network interfaces.
Example:
$ ifconfig eth0
This command displays the configuration of the eth0 interface.
48. ping – Test Network Connectivity
The ping command tests network connectivity to another host.
Example:
$ ping google.com
This command sends ICMP echo requests to google.com.
49. traceroute – Trace the Route to a Host
The traceroute command traces the route packets take to a network host.
Example:
$ traceroute google.com
This command shows the route to google.com.
50. dig – DNS Lookup
The dig command performs DNS lookups.
Example:
$ dig google.com
This command performs a DNS lookup for google.com.
51. echo – Display a Line of Text
The echo command prints text or variables to the terminal.
Example:
$ echo "Hello, World!" Hello, World!
Example with variable:
$ name="Unix" $ echo "Welcome to $name" Welcome to Unix
52. export – Set Environment Variables
The export command sets environment variables for the current session.
Example:
$ export PATH=$PATH:/new/directory $ echo $PATH /usr/local/bin:/usr/bin:/new/directory
53. unset – Remove Environment Variables
The unset command removes environment variables.
Example:
$ unset PATH $ echo $PATH (No output, as PATH is unset)
54. which – Locate a Command
The which command shows the full path of a command.
Example:
$ which ls /bin/ls
55. whereis – Locate Binary, Source, and Manual Pages
The whereis command locates the binary, source, and manual pages for a command.
Example:
$ whereis ls ls: /bin/ls /usr/share/man/man1/ls.1.gz
56. file – Determine File Type
The file command determines the type of a file.
Example:
$ file script.sh script.sh: Bourne-Again shell script, ASCII text executable
57. stat – Display File Status
The stat command displays detailed information about a file or directory.
Example:
$ stat file.txt File: file.txt Size: 1234 Blocks: 8 IO Block: 4096 regular file Device: 802h/2050d Inode: 123456 Links: 1 Access: 2023-10-01 12:34:56.000000000 +0000 Modify: 2023-10-01 12:34:56.000000000 +0000 Change: 2023-10-01 12:34:56.000000000 +0000
58. env – Display Environment Variables
The env command displays all environment variables.
Example:
$ env HOME=/home/user USER=user PATH=/usr/local/bin:/usr/bin:/bin
59. passwd – Change User Password
The passwd command changes the password of the current user.
Example:
$ passwd Changing password for user. (current) UNIX password: Enter new UNIX password: Retype new UNIX password:
60. su – Switch User
The su command switches to another user.
Example:
$ su root Password: # (Now you are the root user)
61. sudo – Execute Commands as Superuser
The sudo command allows a permitted user to execute a command as the superuser.
Example:
$ sudo apt-get update [sudo] password for user:
62. shutdown – Shutdown or Restart the System
The shutdown command shuts down or restarts the system.
Example (shutdown):
$ sudo shutdown -h now
Example (restart):
$ sudo shutdown -r now
63. reboot – Restart the System
The reboot command restarts the system.
Example:
$ sudo reboot
64. who – Display Logged-in Users
The who command displays information about currently logged-in users.
Example:
$ who user tty1 2023-10-01 12:34 user pts/0 2023-10-01 12:35 (192.168.1.1)
65. whoami – Display Current User
The whoami command displays the username of the current user.
Example:
$ whoami user
66. groups – Display User Groups
The groups command displays the groups a user belongs to.
Example:
$ groups user adm cdrom sudo dip plugdev lpadmin sambashare
67. id – Display User and Group Information
The id command displays user and group information.
Example:
$ id uid=1000(user) gid=1000(user) groups=1000(user),4(adm),24(cdrom),27(sudo)
68. uname – Display System Information
The uname command displays system information.
Example:
$ uname -a Linux hostname 5.4.0-42-generic #46-Ubuntu SMP Fri Jul 10 00:24:02 UTC 2020 x86_64 GNU/Linux
69. hostname – Display or Set System Hostname
The hostname command displays or sets the system’s hostname.
Example:
$ hostname hostname
70. date – Display or Set the System Date and Time
The date command displays or sets the system date and time.
Example:
$ date Mon Oct 1 12:34:56 UTC 2023
71. cal – Display a Calendar
The cal command displays a calendar.
Example:
$ cal
October 2023
Su Mo Tu We Th Fr Sa
1 2 3 4 5 6 7
8 9 10 11 12 13 14
15 16 17 18 19 20 21
22 23 24 25 26 27 28
29 30 31
72. sleep – Delay for a Specified Time
The sleep command pauses the execution for a specified time.
Example:
$ sleep 5 (Command pauses for 5 seconds)
73. time – Measure Command Execution Time
The time command measures the execution time of a command.
Example:
$ time ls real 0m0.002s user 0m0.001s sys 0m0.001s
74. bc – Arbitrary Precision Calculator
The bc command is a calculator for arbitrary precision arithmetic.
Example:
$ echo "5 + 7" | bc 12
75. factor – Display Prime Factors
The factor command displays the prime factors of a number.
Example:
$ factor 42 42: 2 3 7
76. zip and unzip – Compress and Decompress Files
The zip command compresses files into a .zip archive, and unzip extracts them.
Example (compress):
$ zip archive.zip file1.txt file2.txt
Example (decompress):
$ unzip archive.zip
77. rsync – Synchronize Files and Directories
The rsync command synchronizes files and directories between two locations.
Example:
$ rsync -av /source/directory /destination/directory
78. mount – Mount File Systems
The mount command attaches a file system to a directory.
Example:
$ sudo mount /dev/sdb1 /mnt
79. umount – Unmount File Systems
The umount command detaches a file system from a directory.
Example:
$ sudo umount /mnt
80. dd – Convert and Copy Files
The dd command is used for low-level copying and conversion of files.
Example (create a bootable USB):
$ sudo dd if=image.iso of=/dev/sdb bs=4M status=progress
81. fdisk – Partition Table Manipulator
The fdisk command manipulates disk partition tables.
Example:
$ sudo fdisk -l
82. mkfs – Create a File System
The mkfs command creates a file system on a partition.
Example:
$ sudo mkfs.ext4 /dev/sdb1
83. fsck – File System Consistency Check
The fsck command checks and repairs file systems.
Example:
$ sudo fsck /dev/sdb1
84. lsof – List Open Files
The lsof command lists files opened by processes.
Example:
$ lsof | grep /home/user
85. strace – Trace System Calls
The strace command traces system calls and signals.
Example:
$ strace ls
86. nc (netcat) – Network Utility
The nc command is a versatile networking tool for reading and writing data across networks.
Example (listen on a port):
$ nc -l 1234
Example (connect to a port):
$ nc localhost 1234
87. nmap – Network Mapper
The nmap command is used for network discovery and security auditing.
Example:
$ nmap 192.168.1.1
88. iptables – Configure Firewall Rules
The iptables command configures firewall rules.
Example (allow SSH):
$ sudo iptables -A INPUT -p tcp --dport 22 -j ACCEPT
89. crontab – Schedule Tasks
The crontab command schedules tasks to run at specific times.
Example (edit crontab):
$ crontab -e
Example (list crontab):
$ crontab -l
90. atq – List Scheduled Jobs
The atq command lists pending scheduled jobs.
Example:
$ atq
91. atrm – Remove Scheduled Jobs
The atrm command removes scheduled jobs.
Example:
$ atrm 1
92. screen – Terminal Multiplexer
The screen command allows you to manage multiple terminal sessions.
Example (start a new session):
$ screen
Example (detach from session):
Ctrl+A, D
93. tmux – Terminal Multiplexer
The tmux command is another terminal multiplexer.
Example (start a new session):
$ tmux new -s mysession
94. w – Display Logged-in Users and Their Activities
The w command shows who is logged in and what they are doing.
Example:
$ w
95. last – Display Login History
The last command displays the login history of users.
Example:
$ last
96. finger – Display User Information
The finger command displays information about users.
Example:
$ finger user
97. chroot – Change Root Directory
The chroot command changes the root directory for a command.
Example:
$ sudo chroot /new/root /bin/bash
98. ldd – List Shared Library Dependencies
The ldd command lists shared libraries required by a program.
Example:
$ ldd /bin/ls
99. nm – List Symbols in Object Files
The nm command lists symbols in object files.
Example:
$ nm /bin/ls
100. objdump – Display Object File Information
The objdump command displays information about object files.
Example:
$ objdump -d /bin/ls
101. strings – Extract Strings from Files
The strings command extracts printable strings from files.
Example:
$ strings /bin/ls
102. hexdump – Display File Contents in Hexadecimal
The hexdump command displays file contents in hexadecimal format.
Example:
$ hexdump -C file.txt
103. xxd – Create a Hex Dump
The xxd command creates a hex dump of a file.
Example:
$ xxd file.txt
104. base64 – Encode/Decode Data
The base64 command encodes or decodes data in Base64 format.
Example (encode):
$ echo "Hello" | base64
Example (decode):
$ echo "SGVsbG8=" | base64 --decode
105. shuf – Generate Random Permutations
The shuf command generates random permutations of input lines.
Example:
$ shuf -i 1-10
These commands cover a wide range of functionalities, from system administration to network management and file manipulation. Let me know if you’d like further details or examples!
Conclusion
Unix commands are powerful tools that allow users to interact with the operating system efficiently. By mastering these commands in Unix with examples, you can perform a wide range of tasks, from basic file management to advanced system administration. Whether you’re a beginner or an experienced user, understanding these commands will help you get the most out of your Unix-based system.
Remember, practice is key to becoming proficient with Unix commands. Try out these examples on your own system, and don’t hesitate to explore the manual pages (man) for more information on each command. With time and experience, you’ll find that the command line is an incredibly powerful and flexible tool for managing your system.
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