Shell cheat sheet: everyday commands

Keep this page open while you learn the terminal. Every command works in bash and zsh on Linux and macOS unless noted. Add --help to most commands, or run man command, for the full list of options.

Moving around

pwd                 # where am I?
ls                  # list files
ls -la              # long format, including hidden dotfiles
ls -lh              # human-readable sizes
cd projects         # go into a folder
cd ..               # up one level
cd ~   (or just cd) # home folder
cd -                # back to the previous folder

Press Tab to complete file and command names, and the Up arrow or Ctrl+R to search your history. Quote paths with spaces: cd "My Files".

Creating, copying and moving

mkdir notes                 # new folder
mkdir -p a/b/c              # create parent folders too
touch todo.txt              # empty file, or update its timestamp
cp todo.txt backup.txt      # copy a file
cp -r src/ src-copy/        # copy a folder
mv old.txt new.txt          # rename
mv report.pdf ~/Documents/  # move

cp and mv silently overwrite an existing destination. Add -i to be asked first, or -n to never overwrite.

Deleting, carefully

rm file.txt          # delete a file: there is no trash can
rm -i *.log          # ask before each file
rmdir empty-folder   # only removes empty folders
rm -r old-folder     # delete a folder and everything in it

• rm does not move files to the trash. They are gone.
• Before a risky delete, run the same pattern with ls first: ls *.log, then rm *.log.
• Be very careful with rm -rf and variables. If $DIR is empty, rm -rf "$DIR"/* targets /*. In scripts, use "${DIR:?}", which stops with an error when the variable is unset or empty.
• Never run commands you do not understand that combine sudo and rm.

Viewing files

cat file.txt          # print the whole file
less big.log          # scroll; q quits, /word searches
head -n 20 file.txt   # first 20 lines
tail -n 50 app.log    # last 50 lines
tail -f app.log       # follow a growing log, Ctrl+C to stop
wc -l file.txt        # count lines

Searching

find . -name "*.md"                 # files by name, below the current folder
find . -type d -name node_modules    # folders only
find . -type f -size +100M           # files over 100 MB
find . -mtime -1                     # changed in the last 24 hours
grep -rn "TODO" src/                 # text inside files, with line numbers
grep -rl "apiKey" .                  # only list matching file names
grep -rn --include='*.py' "import" . # limit to certain files

Permissions and ownership

ls -l script.sh            # show permissions
chmod +x script.sh         # make executable
chmod 644 notes.txt        # rw-r--r--
sudo chown ana:ana file    # change owner and group

Processes and ports

ps aux | grep node         # find a process
top                        # live view; q quits (htop is friendlier if installed)
kill 12345                 # ask process 12345 to stop (SIGTERM)
kill -9 12345              # force stop (SIGKILL), last resort
lsof -i :3000              # what uses port 3000?
jobs; fg; bg               # manage jobs started from this shell
some-command &             # run in the background

Ctrl+C interrupts the running command, Ctrl+Z suspends it (resume with fg), and Ctrl+D ends input or closes the shell.

Disk space

df -h              # free space per disk
du -sh *           # size of each item here
du -sh ~/Downloads # size of one folder

Archives and downloads

tar -czf site.tar.gz site/   # create a gzip archive
tar -xzf site.tar.gz         # extract it
zip -r site.zip site/        # zip a folder
unzip site.zip
curl -O https://example.com/file.tar.gz   # download keeping the name
curl -s https://api.github.com | head    # print a response

History and shortcuts

history | tail -n 20   # recent commands
!!                     # repeat the last command
sudo !!                # repeat it with sudo

macOS vs Linux notes

• macOS ships BSD versions of many tools, so some flags differ from Linux’s GNU versions. Notable cases are sed -i, date and stat.
• To get GNU tools on macOS, install them with Homebrew (for example coreutils, gnu-sed). They are installed with a g prefix, such as gsed.
• The default shell on current macOS is zsh; most Linux distributions default to bash.