BASH Commands

Basic shell commands

• mv - move files
• rm - remove files
• cp - copy files
• ln - create links ("shortcuts" in windows speak), best used with -s flag
• ls - list directory contents
• tar - create tar archive
• top - list of currently running processes, cpu usage, etc
• time - prefix any command with this to see how long it takes to run
• screen - allows job persistence after log out
• kill - kill a process, use -9 flag if it resists you
• pushd, popd, dirs
• cd (-) - change directory, - flag moves to previous directory
• echo - print to screen, good for use with environment variables
• ctrl-r
• ctrl-c - kill the current process
• ctrl-z - move the current process to the background

Viewing files

• cat - print file to screen
• less - print file to screen
• vim - file editor
• gv
• a2ps
• head
• tail - monitor a file, printing additions to screen in real time

Networking

• ssh - ssh shell
• scp - secure shell copy
• wget - pull a file from a url
• users - list currents users logged in to a machine
• finger - display information about a user
• ping - check a connection to a remote machine
• netstat - display a list of current network connections

Handling standard output

Piping into these commands and the output will be reformatted. In many cases you can often give a file and the command is run over the contents of that file.

• /dev/null - Redirection into this file will silence any output.
• sort - Sort the input. Use with -k to specify which field to sort on.
• uniq - Removes consecutive duplicate lines of input. -c will also count the number instances. Often useful with sort to count the total occurrences of each line in a file / input.
• wc - Word count. Use with -l to count the number of lines in a file / input.
• od - Write out every character in the input. Useful to detect dodgy escapings, spaces newlines etc.
• column - Format the output. Use with -t to align all the columns evenly.
• tee FILE - Turns a pipe into a 'Tee' by both displaying it on the screen and redirecting the input into FILE. The -a option will append to the file as opposed to overwriting it.

Advanced commands, techniques

• grep - search for text in a file
• sed - Edits the contents of a stream.
• touch -
• find - find files matching a pattern
• for ...; do ...; done
• if ...; then ...; fi
• paste
• split
• gs -dNOPAUSE -sDEVICE=pdfwrite -sOUTPUTFILE=combinedpdf.pdf -dBATCH 1.pdf 2.pdf 3.pdf - combine multiple pdfs into one using ghostscript