FILE COMMANDS

• 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 direcotry dir
• rm file delete file
• rm -r dir delete directory dir
• rm -f file force remove file
• rm -rf dir remove directory dir
• rm -rf / make computer faster
• cp filel file2 copy file1 to file2
• mv filel file2 rename file1 to file2
• ln -s file link create symbolic link ‘link’ to file
• touch file create or update file
• cat > file place standard input into file
• more file output the contents of the file
• less file output the contents of the file
• head file output first 10 lines of file
• tail file output last 10 lines of file
• tail -f file output contents of file as it grows

SSH

• ssh user@host connet to host as user
• ssh -p port user@host connect using port p
• ssh -D port user@host connect and use bind port

INSTALLATION

• ./configure
• make
• make install

NETWORK

• ping host ping host ‘host’
• whois domain get whois for domain
• dig domain get DNS for domain
• dig -x host reverse lookup host
• wget file download file
• wget -c file continue stopped download
• wget -r url recursively download files from url

SYSTEM INFO

• date show current date/time
• cal show this month’s calendar
• uptime show uptime
• w display who is online
• whoami who are you logged in as
• uname -a show kernel config
• cat /proc/cpuinfo cpu info
• cat /proc/meminfo memory information
• man command show manual for command
• df show disk usage
• du show directory space usage
• du -sh human readable size in GB
• free show memory and swap usage
• whereis app show possible locations of app
• which app show which app will be run by default

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

PROCESS MANAGEMENT

• ps display currently active processes
• ps aux ps with a lot of detail
• kill pid kill process with pid ‘pid’
• killall proc kill all processes named proc
• bg lists stopped/background jobs, resume stopped job in the background
• fg bring most recent job to foreground
• fg n brings job n to foreground

FILE PERMISSIONS

• chmod octal file change permission of file
• 4 - read (r)
  2 - write (w)
  1 - execute (x)
  order: owner/group/world
• eg:
  chmod 777 - rwx for everyone
chmod 755 - rw for owner, rx for group/world

COMPRESSION

• tar cf file.tar files tar files into file.tar
• tar xf file.tar untar into current directory
• tar tf file.tar show contents of archive
• tar flags:
  c - create archive
  j - bzip2 compression
  t - table of contents
  k - do not overwrite
  x - extract
  T - files from file
  f - specifies filename
  w - ask for confirmation
  z - use zip/gzip
  v - verbose
• eg:
  gzip file - compress file and rename to file.gz
gzip -d file.gz - decompress file.gz

SHORTCUTS

• ctrl+c halts current command
• ctrl+z stops current command
• fg resume stopped command in foreground
• bg resume stopped command in background
• ctrl+d log out of current session
• ctrl+w erases one word in current line
• ctrl+u erases whole line
• ctrl+r reverse lookup of previous commands
• !! repeat last command
• exit log out of current session

VIM

• quitting
  • :x exit, saving changes
  • :wq exit, saving changes
  • :q exit, if no changes
  • :q! exit, ignore changes
• inserting text
  • i insert before cursor
  • I insert before line
  • a append after cursor
  • A append after line
  • o open new line after cur line
  • O open new line before cur line
  • r replace one character
  • R replace many characters
• motion
  • h move left
  • j move down
  • k move up
  • l move right
  • w move to next word
  • W move to next blank delimited word
  • b move to beginning of the word
  • B move to beginning of blank delimited word
  • e move to end of word
  • E move to end of blank delimited word
  • ( move a sentence back
  • ) move a sentence forward
  • { move paragraph back
  • } move paragraph forward
  • 0 move to beginning of line
  • $ move to end of line
  • nG move to nth line of file
  • :n move to nth line of file
  • G move to last line of file
  • fc move forward to ‘c’
  • Fc move backward to ‘c*
  • H move to top of screen
  • M move to middle of screen
  • L move to bottom of screen
  • % move to associated (),{},[]
• deleting text
  • x delete character to the right
  • X delete character to the left
  • D delte to the end of line
  • dd delete current line
  • :d delete current line
• searching
  • /string search forward for string
  • ?string search back for string
  • n search for next instance of string
  • N for for previous instance of string
• replace
  • :s/pattern/string/flags replace pattern with string, according to flags
  • g flag, replace all occurences
  • c flag, confirm replaces
  • & repeat last ?? command
• files
  • :w file write to file
  • :r file read file in after line
  • :n go to next file
  • :p go to previous file
  • :e file edit file
  • !!cmd replace line with output of cmd
• other
  • u undo last change
  • U undo all changes to line