Data

Tools

Indexes

Applications

Experiments

Awesome

An open API service indexing awesome lists of open source software.

https://github.com/estherslabbert/linux-and-bash-commands

Cheat sheet for Linux/Bash commands (can be used in writing scripts).
https://github.com/estherslabbert/linux-and-bash-commands

bash cheatsheet commands linux-shell scripting

Last synced: about 1 year ago
JSON representation

Cheat sheet for Linux/Bash commands (can be used in writing scripts).

Awesome Lists containing this project

README 

          
# Bash Commands



- `whoami`: lists the current user's username.

- `date`: outputs current date and time system is running according to.

- `clear`: clears the terminal so that you are able to type in a fresh terminal with unnecessary distractions from previous commands.

- `ls`: lists visible files and folders in current directory.

- `ls -a`: lists invisible files and folders in current directory.

- `ls -l`: list permissions and associated files.

- `cd` or `cd ~` or `cd ../..` or `cd /`: takes you to the home directory (`C:\Users\username` or `home/ubuntu` etc.). (change directory)

- `cd C:/Users/username/folder1` or `cd ~/folder1`: takes you to the directory 'folder1' at the path `C:\Users\username\folder1`.

- `cd ..`: takes you back one folder.

- `pwd`: outputs current location path. (print working directory)

- `mkdir directory1`: makes a folder/directory called 'directory1' in the current location.

- `touch file-name.txt`: modify file 'file-name.txt' or create file 'file-name.txt' if none exists.

- `cat file-name.txt`: output contents of file called 'file-name.txt'. (concatenates and displays files)

- `cat file-name.txt | head -n5` or `head -n5 file-name.txt`: display the first 5 lines of the file 'file-name.txt'. (Change number to be number of lines you want to select).

- `cat file-name.txt | tail -n5` or `tail -n5 file-name.txt`: display the last 5 lines of the file 'file-name.txt'. (Change number to be number of lines you want to select).

- `echo "Any message you would like the terminal to output"`: output a message to the terminal to be read.

- `echo "A message" > file-name.txt`: replace contents of 'file-name.txt' with the echoed message "A message".

- `echo "Additional message" >> file-name.txt`: appends the echoed message "Additional message" to the 'file-name.txt' file.

- `test -f file-name.txt && echo "file exists" || echo "file does not exist"`: check if a file exists in the current repository/directory.

- `wc file-name.txt`: display the number of lines, words, and/or bytes of output.

- `wc -m < file-name.txt` or `cat file-name.txt | wc -m`: display the number of characters (includes new line characters) in the file 'file-name.txt' without the file name in the output.

- `wc -m file-name.txt`: display the number of characters (includes new line characters) in the file 'file-name.txt' and the file name.

- `wc -c < file-name.txt`  or `cat file-name.txt | wc -c`: display the number of bytes in the file 'file-name.txt' without the file name in the output.

- `wc -c file-name.txt`: display the number of bytes in the file 'file-name.txt'.

- `wc -l file-name.txt`: display the number of lines in the file 'file-name.txt' and the file name.

- `wc -l < filename.txt` or `cat file-name.txt | wc -l` or `sed -n '$=' file-name.txt`: display the number of lines in the file 'file-name.txt' without the file name in the output.

- `cat -n file-name.txt`: displays each line, ennumerated in the file 'file-name.txt' (e.g. where each /n is a new line in the output: /n1 First line. /n2 Second line. /n3 Third line).

- `sed -n '=' file-name.txt`: displays numbers for each line in the file 'file-name.txt' (e.g. where each /n is a new line in the output: /n1 /n2 /n3).

- `mv file1 file-name.txt`: renames 'file1' to be 'file-name.txt'. (Note that, if you use mv to give a file a name that already exists, it will cause that file to be overwritten)

- `mv file-name.txt ~/folder/file-name.txt`: moves 'file-name.txt' to location '~/folder/file-name.txt'.

- `rm file-name.txt`: removes file 'file-name.txt'.

- `rm -r folder1`: removes directory and its contents. (Note: The -r option means "remove files recursively", i.e. it removes all files you specify, and if that file is a directory, it removes all files in that directory. If that directory has sub-directories of its own, it removes those, etc.)

- `rm -r folder1/*`: removes all the contents of 'folder1' directory while still keeping the 'folder1' directory itself.

- `rmdir folder1`: removes 'folder1' directory if empty.

- `cp file1.txt file2.txt`: copies 'file1.txt' to another file called 'file2.txt'.

- `diff file1.txt file2.txt`: shows differences between 'file1.txt' and 'file2.txt' or nothing if there are no differences.

- `chmod u+x file-name.txt`: changes permissions of the file 'file-name.txt', giving the user executable permissions for the file. (Before `+` or `-` you can choose `u` for user, `g` for group, and or `o` for other to specify who the change is for (can leave blank or use `a` or `ugo` for all). after the `+` or `-` you can choose `w` for write, `r` for read and or `x` for execute permissions. The `+` gives the permission(s) and the `-` removes the permission(s).)

- `ps`: gives a list of processes running and their process IDs.

- `kill process-id`: kills a process if you replace `process-id` with the actual process ID (PID).

- `variable_name=variable_value`: sets a variable called `variable_name` to be the value `valriable_value`, and can be called on using `echo $variable_name` or `echo ${variable_name}` when working with multiple variables or punctuation. (Note: variables are case-sensitive, connot contain spaces or special characters except `_` and it must start with a letter. If you want things to be as they are without using an escape character then use `'` `'`)

- `env` or `printenv`: lists all environment variables.

- `printenv ENV_VAR` or `echo $ENV_VAR`: returns the value of the environment variable 'ENV_VAR'.

- `grep "part-of-word-or-sentence" ./path/to/file-name.txt`: searches for and returns the line that contains "part-of-word-or-sentence" in './path/to/file-name.txt'. (using `-i` with grep makes its search case-insensitive, `-i "^ip"` will search for lines that start with 'ip', `-i "ip$"` will search for lines ending in 'ip', `-iv` will exclude the lines containing whatever is specified.)

- `grep -q "part-of-word-or-sentence" file-name.txt`: runs grep command in quiet mode, so it returns no output.

- `echo $?`: gets error or run code (usually between 1-155) for last command (0 if successful).



For additional information: [Charmm gui Unix lessons](https://charmm-gui.org/?doc=lecture&module=unix&lesson=1)



## Additional useful things to know



`\` is an escape character. (Example use case: So if you have a file name and have not placed it in quotation marks that has a space you can use the escape character before the space to make sure the file name is correctly referenced. - can be used for other special characters that are not meant to perform a function)



`|` is a pipe operator and is used to connect commands together (form more specific or complex commands).



Using `sudo` before a command elevates the command to have admin privileges.



On Ubuntu systems environment variables are stored in the `.bashrc` file located at `~/.bashrc`.



If using [`vi`](https://www.redhat.com/sysadmin/introduction-vi-editor) the commands are different.



See [`nano`](https://www.hostinger.co.uk/tutorials/how-to-install-and-use-nano-text-editor) commands for additional file writing and [`sed`](https://www.geeksforgeeks.org/sed-command-in-linux-unix-with-examples/) commands for editing files without even opening them.



[`cURL`](https://blog.hubspot.com/website/curl-command#:~:text=Client%20URL%20) commands receive the URL to transfer data to — or receive data from — along with other options for different purposes (often seen when installing specific versions of software).



The [`time`](https://www.hostinger.co.uk/tutorials/linux-time-command/) command can be used to see how long it takes to execute a certain command and usually follows the format `time command` (where `command` is an actual command).



[`cron`](https://opensource.com/article/21/7/cron-linux#:~:text=The%20cron%20system%20is%20a,run%20commands%20on%20a%20schedule.&text=30%20readers%20like%20this.&text=SA%20Seth%20Kenlon-,The%20cron%20system%20is%20a%20method%20to%20automatically%20run%20commands,a%20file%20called%20a%20crontab.) commands are to deal with scheduled jobs.



To securely log in to a remote machine and execute commands use `ssh user@host` (basic syntax).



`#!/bin/bash` is the line necessary at the start of a shell script file. (`#!` is known as a shebang)



`*` is a wild card character, meaning it is used as a placeholder to signify all or everthing (often used with file extensions e.g. `*.txt` means all .txt files in the location specified).



`&&` is used to run 2 commands from one line (e.g. `sudo apt-get update -y && sudo apt-get upgrade -y` gets updates and upgrades on linux).



`Ctrl` + `C` cancels a process or logs you out.



`exit` will end a terminal session or log you out if logged in to a remote session.



`Ctrl` + `Z` suspends a process. `bg` moves the suspended process to the background. `fg` moves the process to the foreground.



`Ctrl` + `D` logs you out of an interface.



`Ctrl` + `Ins` copies the selected characters from the Bash terminal and `Shift` + `Ins` pastes into a Bash terminal.