Monday, January 17, 2011

Unix/Linux Command Reference

Once again hello to all of my reader! I have collected some of the commands of Linux/Unix, what i have been using on my ubuntu from last few years.

File Commands
  • ls - directory listing
  • Is -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
  • In -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
Process Management

  • 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
File Permissions

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.

SSH

  • 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

Searching

  • 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

System Info

  • 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

Compression

  • 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


Network


  • 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


Installation


Install from source:
./configure
make
make install
dpkg -i pkg.deb - install a package (Debian)
rpm -Uvh pkg.rpm - install a package (RPM)

Shortcuts

  • 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
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