Bash / Linux CLI

Most important Bash Commands

Master the terminal with essential Bash commands, package management, file handling, and permissions. Use Cmd + F or Notion’s search to find commands instantly. This guide is meant to cover the most basic and useful commands and their options and is not exhaustive.

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📚 Index

📁 Navigation

To navigate files and directories using a command line interface (CLI), such as Terminal on macOS or Linux, you can utilize a variety of commands that help you move around the file system efficiently. The tab key can be used to autocomplete codes, eg when writing folder paths, and the ↑  and  ↓ keys can be used to cycle through previous commands.

⚠️ For commands that accept a location, omitting it defaults to the current working directory .. Some commands like pwd do not allow specifying a location at all.

pwd

Print folder path of current working directory

cd

Change current working directory

- previous directory → can be used to jump between two folders

🔀 Path Shortcuts
Use to quickly reference directories
. current directory
.. parent directory, eg cd ../.. quickly goes up two levels
~ home directory, eg /Users/<username>
/ root directory, if used at beginning of location path

ls

List files and folders

-a Include hidden files, ie those starting with .
-l Long listing format with detailed information
-h → Human-readable sizes, eg 1K for 1024 bytes, used with -l
-t Sort by modification time from recent to oldest
-S Sort by size
-r Reverse sort order, useful with -t or -S
-R List subdirectories recursively, ie up to the deepest level
-1 List only 1 file per line, useful for piping or scripting
-d List targets directly, without contents of directories, eg with: ls -d */

*️⃣ Wildcards
Use wildcards to match multiple filenames:
* Matches any amounts of characters, e.g. ls *.txt lists all .txt files
.* Matches any hidden files (names start with .), which * alone doesn’t
? Matches exactly one character, e.g. ls a?.txt matches a1.txt, a3.txt
[abc] Matches one character from the set, e.g. ls a[12].txt → a1.txt, a2.txt

mkdir

Make new directory

-p Create parent directories if needed, eg mkdir -p parent/child
-v ”Verbose output” - Show a message for each created directory
-m Set permissions, eg mkdir -m 755 new_directory , 755 = writable by owner

🧱 Basic Command Structure
Many command lines follow this order:
<command> <options> <option-values or sources> <target or location>
e.g. mkdir -m 755 new_directory
→ command: mkdir | option: -m | value: 755 | target: new_directory

touch

Create a new file or update its timestamps

-a Update only the access time
-m Update only the modification time
-c Do not create any files if non-existent

clear

Clear the terminal view ← this won’t undo any commands

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📄 File Management

Learn to manipulate directories and files from the command line. For commands that allow dealing with multiple files at once the last argument will act as the destination, eg when creating or copying files.

cat

Show file contents or concatenate multiple files to a single output

-n Add numbers to each line
-b Add numbers to non-blank lines only
-s Suppress repeated blank-lines, only showing up to one

cp

Copy files and directories

-R Copy directories recursively → Must be used when copying folders
-i Interactive — ask before overwriting existing files
-f Force overwrite and delete destination if needed
-u Only overwrite existing files if their modification time is older
-a Create exact clone by copying recursively and preserving all attributes
-p Preserve timestamps, ownerships and permissions
-v Verbose — display what is being copied

mv

Move files and folders or rename them if the path doesn’t change

-i Interactive — ask before overwriting existing files
-v Verbose — display what is being copied

rm

Remove files and folders irrevocably ⚠️

-r Delete directories recursively → Required when deleting folders
-i Interactive — ask before deleting each file
-f Force delete without prompting, even if files don’t exist
-v Verbose — display what is being copied

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🔁 Redirection & Pipes

Learn to redirect input and output to and from files and commands and connect processes in the shell.

echo

Output a line of text or a variable's value

-n Don't add a new line at the end
-e Enable backslash escapes, eg  for new lines,   for tabs, etc.

🔀 Redirect Operators
Can be used with commands that write output like echo:
> Redirect output → Saves to a file and overwrites it if it already exists ⚠️
>> Append output → Saves to the end of a file without overwriting content
| Pipe to next command → Sends output as input for command after |
< Redirect input → Take input from a file
<< Takes multiline input until a defined delimiter, eg: cat << END (lines) END

tee

Show input on screen while also saving it to a file

-a Append input to a file rather than overwriting it

wc

Count the number of lines, words, and bytes from input

-l Only count the number of lines
-w Only count the number of words
-c Only count the number of bytes
-m Only count the number of characters

sort

Sort lines of text alphabetically

-r Sort in reverse order
-n Sort numbers numerically, not alphabetically, eg 2 before 10
-k Sort by column (delimiter: space), eg -k2,2 (only col 2) or -k2 (col 2 and beyond)
-u Remove duplicate lines ← must be adjacent, so sort first
-t Set a custom delimiter for columns, eg ",", and use with -k
-o Output result to file
-b Ignore leading blanks
-f Ignore case, ie treat uppercase and lowercase as equal

uniq

Remove adjacent duplicate lines

-c Prefix lines with the number of adjacent occurrences
-d Show only adjacent duplicate lines
-u Show only unique lines, ie those that appear exactly once in the input
-i Ignore case, ie treat uppercase and lowercase as equal

grep

Search for specific text and output the matching lines

-i  Ignore case, ie treat uppercase and lowercase as equal
-r  Search directories recursively → Required for folder search
-n  Show the line numbers where each match appears
-v  Show lines that do not match the search text
-l List files that contain matches only
-c Show count of matching lines per file
-o Only output the matched text, not the whole lines → Eg for use with | wc
-e Search for multiple terms separately, by using -e before each

sed

Perform temporary line-by-line first-instance edits

-e  Apply multiple edits at once, eg -e '...' -e '...'
-i  Make edits permanent in-place — no backup, no output
-n  No default output → use with custom printing
-f Run multiple '///' commands from a file instead of using -e
's///' Substitute like 's/old/new/'
'///p' Print the edited lines → Use with -n to print only matches
'///g' Apply edits globally, not just the first match per line