Linux cheatsheet

my linux cheatsheet

#--- install/remove packages
apt-get update            # Fetches the list of available updates
apt-get upgrade           # Strictly upgrades the current packages
apt-get dist-upgrade      # Installs updates (new ones)
apt-get autoclean         # This command removes .deb files for packages 
                          # that are no longer installed on your system.
apt-get clean             # Remove the installed deb packages
apt-get remove <package>  # This command removes an installed package, leaving configuration files intact.
apt-get purge <package>   # This command completely removes a package and the associated configuration files. 
apt-get autoremove        #This command removes packages that were installed by other packages and are no longer needed.
apt-get autoremove <package> #This command removes an installed package and dependencies.
dpkg-query -l             # List all packages installed
dpkg-query -l 'foo*'      # List packages using a search pattern
apt-cache search 'foo'    # Search for the package that you want to install

pwd                       # Print the current directory
history                   # Show the history of command lines executed up to this moment.
		            Commands prepend by a space will be executed but won't show up in the history.
		            After the user logs out from Bash, history is saved into ~/.bash_history
!n 		          # Execute command number n in the command line history 
history -c 	          # Delete command line history
uname -a 	          # Print system information

#--- disk space
df -l                     # Disk free, used to display the amount of available disk space
du -hc --max-depth=1      # Display space used by each directory
env                       # Display the environment variables

#--- print files
cat myfile                # Print a text file
cat myfile1 myfile2 > myfile3   # Concatenate text files
head myfile               # Print the first 10 lines of a text file
head -n 10 myfile
tail myfile               # Print the last 10 lines of a text file
tail -n 10 myfile

#--- search files
grep -iRl 'text'          # Find filenames that contain 'text'
grep -rnw 'text'          # Find 'text' in files (r:recursive, n:linenum, w:whole word)
ack 'text'                # Find 'text' in files (install: ack-grep in ubuntu)

nl myfile 	          # Prepend line numbers to a text file
wc myfile 		  # Print the number of lines, words, and bytes of a text file

uniq myfile 	          # Print the unique lines of a text file, omitting consecutive identical lines
sort myfile 	          # Sort alphabetically the lines of a text file
expand myfile             # Convert tabs into spaces
unexpand myfile           # Convert spaces into tabs

sed s/foo/bar/ myfile 	  # Stream Editor: Replace the first occurrence of foo with bar
sed s/foo/bar/g myfile 	  # Replace all occurrences of foo with bar

tr a-z A-Z <myfile	  # Translate characters: Convert all lowercase into uppercase in a text file 
tr [:lower:] [:upper:] <myfile

#--- copying/moving/removing
cp myfile myfile2 	  # Copy a file
cp myfile mydir/ 	  # Copy a file to a directory

mv myfile myfile2 	  # Rename a file
mv myfile mydir/ 	  # Move a file to a directory
rm myfile 		  # Delete a file
rm -rf <dir>	          # Remove a directory
ln -s <target dir/file> ./[SHORTCUT] # Create a symbolic link
mkdir mydir 	          # Create a directory

touch myfile 	          # Change access/modification timestamp on a file, creating it if it doesn't exist

#--- jobs/monitoring
ps -ef (UNIX options)	  # List all processes
top		          # Monitor processes in realtime
htop
jobs 		          # List all jobs (i.e. processes whose parent is a Bash shell)
ctrl-Z		          # Suspend a job, putting it in the stopped state (send a SIGTSTP)
bg %1 		          # Put job #1 in the background (send a SIGCONT)
fg %1 		          # Resume job #1 in the foreground and make it the current job (send a SIGCONT)
kill %1 		  # Kill job #1


#--- various
ldd --version             # check to see which C library version is used.
whereis <library>         # find location of shared library (ex. whereis libc.so)