Predictive Hacks

Unix Commands Cheat Sheet

unix command

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)

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