Unix/Linux Command Reference
Introduction: This post contains important commands which required most of time when user work on Unix machine. Find commands with description below –
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File Commands
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| ls | Directory listing |
| ls -al | Formatted listing with hidden files |
| cd dir | Change directory to dir |
| cd | Change to home |
| pwd | Show current directory |
| mkdir dir | Create a directory dir |
| rm file | Delete file |
| rm -r dir | Delete directory dir |
| rm -f file | Force remove file |
| rm -rf dir | Force remove directory dir * |
| cp file1 file2 | Copy file1 to file2 |
| cp -r dir1 dir2 | Copy dir1 to dir2; create dir2 if it doesn’t exist |
| mv file1 file2 | Rename or move file1 to file2 if file2 is an existing directory, moves file1 into directory file2 |
| ln -s file link | Create symbolic link link to file |
| touch file | Create or update file |
| cat > file | Places standard input into file |
| more file | Output the contents of file |
| head file | Output the first 10 lines of file |
| tail file | Output the last 10 lines of file |
| tail -f file | Output the contents of file as it grows, starting with the last 10 lines |
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Process Management
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| ps | Display your currently active processes |
| top | Display all running processes |
| kill pid | Kill process id pid |
| killall proc | Kill all processes named proc * |
| bg | Lists stopped or background jobs; resume a Stopped job in the background |
| fg | Brings the most recent job to foreground |
| fg n | Brings job n to the foreground |
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File Permission
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| chmod octal file | Change the permissions of file to octal, which can be found separately for user, group, and world by adding: ● 4 – read (r) ● 2 – write (w) ● 1 – execute (x) Examples: chmod 777 – read, write, execute for all chmod 755 – rwx for owner, rx for group and world For more options, see man chmod. |
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SSH
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| ssh user@host | Connect to host as user |
| ssh -p port user@host | Connect to host on port port as user |
| ssh-copy-id user@host | Add your key to host for user to enable a keyed or passwordless login |
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Searching
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| grep pattern files | Search for pattern in files |
| grep -r pattern dir | Search recursively for pattern in dir |
| command | grep pattern | Search for pattern in the output of command |
| locate file | Find all instances of file |
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System Info
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| date | Show the current date and time |
| cal | Show this month’s calendar |
| uptime | Show current uptime |
| w | Display who is online |
| whoami | Who you are logged in as |
| finger user | Display information about user |
| uname -a | Show kernel information |
| cat /proc/cpuinfo | Cpu information |
| cat /proc/meminfo | Memory information |
| man command | Show the manual for command |
| df | Show disk usage |
| du | Show directory space usage |
| free | Show memory and swap usage |
| whereis app | Show possible locations of app |
| which app | Show which app will be run by default |
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Compression
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| tar cf file.tar files | Create a tar named file.tar containing files |
| tar xf file.tar | Extract the files from file.tar |
| tar czf file.tar.gz files | Create a tar with Gzip compression |
| tar xzf file.tar.gz | Extract a tar using Gzip |
| tar cjf file.tar.bz2 | Create a tar with Bzip2 compression |
| tar xjf file.tar.bz2 | Extract a tar using Bzip2 |
| gzip file | Compresses file and renames it to file.gz |
| gzip -d file.gz | Decompresses file.gz back to file |
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Network
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| ping host | Ping host and output results |
| whois domain | Get whois information for domain |
| dig domain | Get DNS information for domain |
| dig -x host | Reverse lookup host |
| wget file | Download file |
| wget -c file | Continue a stopped download |
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Shortcuts
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| Ctrl+C | Halts the current command |
| Ctrl+Z | Stops the current command, resume with fg in the foreground or bg in the background |
| Ctrl+D | Log out of current session, similar to exit |
| Ctrl+W | Erases one word in the current line |
| Ctrl+U | Erases the whole line |
| Ctrl+R | Type to bring up a recent command |
| !! | Repeats the last command |
| exit | Log out of current session |