Command line cheat sheet

This is my command line cheat sheet. I can refer to this document in the future if I forget a specific command in the future.

Overview

• cat
• cd
• cp
• echo
• grep
• ls
• mkdir
• mv
• nano and the environment
• pwd
• rm
• sed
• sort
• source
• tail
• >
• >>
• |

Commands

cat

• Example
  • $ cat hello.txt
• Description
  • This command outputs the content of a file into the termianl (standard output)

cd

• Example
  • $ cd nameofdirectory
• Description
  • This command changes the current directory. Adding .. moves you up one directory.

cp

• Example
  • $ cd file1.txt file2.txt
• Description
  • This command copies the contents of a file/directory (first args) to another (last arg)

echo

• Example
  • echo hello
• Description
  • This command accepts a standard input (through terminal) string and outputs a standard output (outputted terminal info)

grep

• Example
  • grep Mount mountains.txt
• Description
  • This command is short for Global Regular Expression Print.
  • It searches for lines that match a pattern and returns the results.
• Options
  • -i is used to make the command non case sensitive.
  • -R is used to make the command recursive, so that it searches through the children as well
  • -l is used to make the command output the filenames of of the files with matches, instead of just the lines.

ls

• Example
  • $ ls
• Description
  • This command lists the files in the current working directory.
• Options
  • -a is used to list hidden files/folders (things prefixed with .).
  • -l is used to list everything in a long format.
  • -t is used to list things by the time they were last modified.

mkdir

• Example
  • $ mkdir newdirectoryname
• Description
  • This command creates a new directory.

mv

• Example
  • $ mv myfile ~/myfile
• Description
  • This command files or directories from one place to another.
  • Last argument is the destination.

nano_and_the_environment

• Example
  • $ nano
• Description
  • Built in text editor for terminal.
• ~/.bash_profile
  • alias pd="pwd" is a great way to create keyboard shortcuts for a given bash profile.
  • Environment variables look like $THIS
  • export VARIABLE="value" sets and exports an environment variable.

pwd

• Example
  • $ pwd
• Description
  • This command Prints the Working Directory (hence pwd), showing what directory you are in.

rm

• Example
  • $ rm
• Description
  • This command is used to remove files or directories, permanently.
• Options
  • -r stands for recursive, and is used to murder a directory and all its children.

sed

• Example
  • $ sed 's/snow/rain/g' forests.txt
• Description
  • This command stands for Stream EDitor.
  • It accepts standard input and modifies it using an expression, before outputing it, like search and replace.
• Expression Breakdown
  • s stands for substiution. It is always used when substituting.
  • snow is the search string.
  • rain is the replacement string.
  • g stands for global, it means all isntances of snow will be replaced. Without it, only the first instance of snow per line would get replaced.

sort

• Example
  • $ sort nameoffile.txt
• Description
  • This command takes in standard input and provides standard output, with the output being sorted alphabetically.

source

• Example
  • $ source ~/.bash_profile
• Description
  • Evaluates argument as a list of commands, and runs it in the in the current context (session)

tail

• Example
  • $ tail nameoffile.txt
• Description
  • This command displays the last portion of a file. It accepts optional arguments such as -n which allows you to indicate how many lines from the end of the file you'd like to display.

touch

• Example
  • $ touch keyboard.txt
• Description
  • This command creates a new new empty file inside the current directory, taking the filename as an argument.

uniq

• Example
  • uniq deserts.txt
• Description
  • Takes in input, and outputs data with identical, adjacent lines filtered out.

>

• Example
  • $ echo "hello" > hello.txt
• Description
  • This command redirects output as input.
  • The redirect command in this case redirects the standard output of echo into a file.
  • When written in the other direction, it performs the same function, just the input and output are switched.
  • Used to pass output to a file or stream.

>>

• Example
  • $ cat mountains.txt >> clouds.txt
• Description
  • This command redirects standard output, but has it be appended to the destination, intstead of replacing it.
  • Essentially just an extension of the > command.

|

• Example
  • $ cat volcanoes | wc | cat > islands.txt
• Description  * Used to pass output to a program or utility.