Unix Commands Cheat Sheet

It is very important for every Data Analyst/Scientist to be able to interact with the Command Line Shell. Let’s start with a “cheat sheet” of Basic Linux Commands. This list includes a bunch of different commands that are useful to know when working with Linux.

Managing files and directories

• cd directory: changes the current working directory to the specified one
• pwd: prints the current working directory
• ls: lists the contents of the current directory
• ls directory: lists the contents of the received directory
• ls -l: lists the additional information for the contents of the directory
• ls -a: lists all files, including those hidden
• ls -la: applies both the -l and the -a flags
• mkdir directory: creates the directory with the received name
• rmdir directory: deletes the directory with the received name (if empty)
• rm file: deletes the file, we can either go one-by-one or we delete them all together using the *
• cp old_name new_name: copies old_name into new_name
• mv old_name new_name: moves old_name into new_name
• touch file_name: creates an empty file or updates the modified time if it exists
• chmod modifiers files: changes the permissions for the files according to the provided modifiers; we’ve seen +x to make the file executable
• chown user files: changes the owner of the files to the given user
• chgrp group files: changes the group of the files to the given group

Operating with the content of files

• cat file: shows the content of the file through standard output
• wc file: counts the number of characters, words, and lines in the given file; can also count the same values of whatever it receives via stdin
• file file: prints the type of the given file, as recognized by the operating system
• head file: shows the first 10 lines of the given file
• tail file: shows the last 10 lines of the given file
• less file: scrolls through the contents of the given file (press “q” to quit)
• sort file: sorts the lines of the file alphabetically
• cut -dseparator -ffields file: for each line in the given file, splits the line according to the given separator and prints the given fields (starting from 1)

Additional commands

• echo “message”: prints the message to standard output
• date: prints the current date
• who: prints the list of users currently logged into the computer
• man command: shows the manual page of the given command; manual pages contain a lot of information explaining how to use each command (press “q” to quit)
• uptime: shows how long the computer has been running
• free: shows the amount of unused memory on the current system

Managing streams

These are the redirectors that we can use to take control of the streams of our programs

• command > file: redirects standard output, overwrites file
• command >> file: redirects standard output, appends to file
• command < file: redirects standard input from file
• command 2> file: redirects standard error to file
• command1 | command2: connects the output of command1 to the input of command2

Operating with processes

These are some commands that are useful to know in Linux when interacting with processes.

• ps: lists the processes executing in the current terminal for the current user
• ps ax: lists all processes currently executing for all users
• ps e: shows the environment for the processes listed
• kill PID: sends the SIGINT signal to the process identified by PID
• fg: causes a job that was stopped or in the background to return to the foreground
• bg: causes a job that was stopped to go to the background
• jobs: lists the jobs currently running or stopped
• top: shows the processes currently using the most CPU time (press “q” to quit)