CLI Commands Reference

Essential terminal commands explained in plain English — with examples and the exact words to use when describing them in a standup or code review.

Last reviewed: 29 May 2026

Navigation & File Management

pwd Print Working Directory

Show the full path of the current directory.

Say it "p-w-d"

Example

$ pwd
/home/jane/projects/api

ls List

List files and directories in the current folder.

Say it "l-s"

Example

$ ls
README.md  src/  package.json

$ ls -la         # long format + hidden files
drwxr-xr-x  jane  4096 Jun  1 10:00 .
-rw-r--r--  jane  1234 Jun  1 09:00 README.md

cd Change Directory

Navigate to a different directory.

Say it "c-d"

Example

$ cd src/          # go into src folder
$ cd ..            # go up one level
$ cd ~             # go to your home directory
$ cd -             # go back to the previous directory

mkdir Make Directory

Create a new directory.

Say it "mkdir"

Example

$ mkdir logs
$ mkdir -p src/components/auth   # create nested directories at once

rm Remove

Delete files or directories.

Say it "r-m"

Example

$ rm old-file.txt
$ rm -rf dist/    # recursively delete a directory
                  # WARNING: no recycle bin — permanent!

cp Copy

Copy files or directories.

Say it "c-p"

Example

$ cp config.yml config.yml.bak
$ cp -r src/ src-backup/

mv Move / Rename

Move a file or rename it.

Say it "m-v"

Example

$ mv old-name.ts new-name.ts     # rename
$ mv reports/ /tmp/archive/      # move directory

Viewing File Contents

cat Concatenate and print

Print the entire contents of a file to the terminal.

Say it "cat"

Example

$ cat .env
DATABASE_URL=postgres://...
PORT=3000

less Less

View a file page by page — press q to quit, / to search.

Say it "less"

Example

$ less server.log
# press / then type a word to search
# press q to quit

head Head

Show the first N lines of a file (default 10).

Say it "head"

Example

$ head server.log
$ head -n 50 server.log   # first 50 lines

tail Tail

Show the last N lines of a file. -f follows new output in real time.

Say it "tail"

Example

$ tail server.log
$ tail -n 100 server.log
$ tail -f server.log    # "follow" — watch live log output

grep Global Regular Expression Print

Search for a pattern inside files or command output.

Say it "grep"

Example

$ grep "error" server.log
$ grep -r "TODO" src/               # recursive search
$ grep -i "Error" server.log        # case-insensitive
$ grep -n "port" config.yml         # show line numbers
$ cat server.log | grep "500"       # pipe: filter output

Permissions & Users

chmod Change Mode

Change the read/write/execute permissions of a file.

Say it "chmod"

Example

$ chmod +x deploy.sh            # make a script executable
$ chmod 600 .env                 # owner read/write only
$ chmod 644 README.md            # owner rw, others read-only
$ chmod -R 755 public/           # recursive

chown Change Owner

Change the owner (user and group) of a file or directory.

Say it "chown"

Example

$ chown www-data:www-data html/
$ chown -R jane:staff src/

sudo SuperUser Do

Run a command as the root (administrator) user.

Say it "sudo"

Example

$ sudo apt install nginx
$ sudo systemctl restart nginx
$ sudo nano /etc/hosts

Processes

ps Process Status

List running processes.

Say it "p-s"

Example

$ ps aux                          # all processes, detailed
$ ps aux | grep node              # find Node.js processes

kill Kill

Send a signal to a process, usually to terminate it.

Say it "kill"

Example

$ kill 12345          # send SIGTERM (graceful stop)
$ kill -9 12345       # send SIGKILL (force stop)
$ killall node        # kill all processes named "node"

top / htop Table of Processes / Interactive Process Viewer

Live view of CPU and memory usage by process. htop is the friendly version.

Say it "top / h-top"

Example

$ top
$ htop   # if installed; q to quit, F2 to configure

Networking & Remote

curl Client URL

Make HTTP requests from the command line.

Say it "curl"

Example

$ curl https://api.example.com/health
$ curl -X POST https://api.example.com/users \
  -H "Content-Type: application/json" \
  -d '{"name":"Jane"}'
$ curl -I https://example.com       # headers only

wget Web Get

Download files from a URL.

Say it "wget"

Example

$ wget https://example.com/archive.zip
$ wget -O output.zip https://example.com/archive.zip

ssh Secure Shell

Say it "S-S-H"

Example

$ ssh user@192.168.1.10
$ ssh -i ~/.ssh/my-key.pem ubuntu@ec2-1-2-3-4.compute.amazonaws.com
$ ssh -p 2222 user@example.com        # non-default port

scp Secure Copy Protocol

Copy files between local machine and a remote server over SSH.

Say it "s-c-p"

Example

$ scp file.txt user@server:/home/user/
$ scp user@server:/var/log/app.log ./logs/
$ scp -r dist/ user@server:/var/www/html/

Archives & Compression

tar Tape Archive

Create or extract .tar (and .tar.gz) archives.

Say it "tar"

Example

$ tar -czf archive.tar.gz dist/    # compress folder
$ tar -xzf archive.tar.gz           # extract
$ tar -tzf archive.tar.gz           # list contents without extracting
# Flags: c=create, x=extract, z=gzip, f=filename, t=list

zip / unzip Zip / Unzip

Create or extract .zip archives.

Say it "zip / unzip"

Example

$ zip -r archive.zip dist/
$ unzip archive.zip
$ unzip archive.zip -d output/     # extract to a directory

Environment & Shell

echo Echo

Print text or variable values to the terminal.

Say it "echo"

Example

$ echo "Hello, world!"
$ echo $HOME
$ echo $NODE_ENV

env Environment

List all environment variables, or run a command with a specific environment.

Say it "env"

Example

$ env                        # list all env vars
$ env | grep NODE            # filter env vars
$ env NODE_ENV=production node app.js

export Export

Set an environment variable so child processes inherit it.

Say it "export"

Example

$ export NODE_ENV=production
$ export PORT=3000
$ export DATABASE_URL="postgres://localhost/mydb"

source Source

Run a script in the current shell — useful for loading .env files or updating PATH.

Say it "source"

Example

$ source .env
$ source ~/.bashrc
$ . ~/.zshrc    # dot is an alias for source

which Which

Show the full path of a command executable.

Say it "which"

Example

$ which node
/usr/local/bin/node
$ which python3

man Manual

Show the manual page (documentation) for a command.

Say it "man"

Example

$ man grep
$ man ssh
# press q to quit
# use --help for a short summary: grep --help

Piping & Redirection

| (pipe) Pipe

Send the output of one command as the input to the next.

Say it "pipe"

Example

$ cat server.log | grep "ERROR" | tail -n 20
$ ps aux | grep node
$ ls -la | less

> and >> Redirect output

> overwrites a file with output. >> appends to a file.

Say it "redirect to / append to"

Example

$ echo "build failed" > error.txt    # overwrite
$ cat server.log >> all-logs.txt     # append
$ npm run build 2>&1 | tee build.log  # tee: write to file AND show in terminal

How to Say Commands Aloud

When talking with teammates, you'll describe commands in words. Here's how to translate common command strings into natural spoken English.

You type	You say
`grep -r "error" ./logs`	"grep dash r for error in the logs directory"
`chmod +x deploy.sh`	"chmod plus x deploy dot s-h"
`tail -f app.log`	"tail dash f app dot log"
`ls -la`	"l-s dash l-a"
`ssh -i key.pem user@host`	"S-S-H dash i key dot pem user at host"
`curl -X POST`	"curl dash X POST"
`rm -rf dist/`	"r-m dash r-f dist slash"
`ps aux \| grep node`	"p-s aux pipe grep node"
`tar -czf archive.tar.gz src/`	"tar dash c-z-f archive dot tar dot g-z s-r-c slash"
`kill -9 1234`	"kill dash nine twelve-thirty-four"

General rules

Flags: Say "dash" for - and "double-dash" for --. "-v" = "dash v", "--verbose" = "double-dash verbose".
Path separators: Say "slash" for / and "backslash" for \. Say "dot" for . when it's part of a filename.
Pipe: Say "pipe" for |.
Tilde: Say "tilde" for ~ (home directory).
Asterisk: Say "star" or "wildcard" for *.
Redirects: Say "redirect to" for > and "append to" for >>.
Extensions: Spell or read them: .sh = "dot s-h" or "shell script", .tar.gz = "dot tar dot g-z".

CLI Phrasebook

Phrases engineers actually use when talking about terminal work.

"I'm SSHing into the server.": I'm connecting to the remote server via SSH.
"Let me grep the logs for the error.": I'll search the log file for the error message.
"I'll tail the log file to watch it live.": I'll run tail -f to watch new log entries in real time.
"I need to chmod the script to make it executable.": I'll run chmod +x on the script file.
"Let me curl the endpoint.": I'll send an HTTP request to the API endpoint using curl.
"I'll SCP the file over.": I'll copy the file to the remote server using scp.
"Check if port 3000 is in use.": Run: lsof -i :3000 or ss -ltnp | grep 3000.
"Kill the process on port 8080.": Find the PID (lsof -i :8080) then kill that PID.
"I'll tar up the build folder.": I'll compress the build directory into a .tar.gz archive.
"Export the env var first.": Run export VARIABLE_NAME=value before running the command.
"Pipe the output to grep.": Add | grep "pattern" to the end of the command.
"The script isn't executable — chmod it.": Run chmod +x script.sh to give it execute permission.

Frequently Asked Questions

What is the difference between head and tail?

head prints the first N lines of a file (default 10), while tail prints the last N lines. tail also supports the -f ("follow") flag, which keeps the terminal open and streams new lines as they are appended — the standard way to watch a live log file in real time.

What is the difference between rm -r and rm -rf?

rm -r deletes a directory and everything inside it recursively, but still prompts for confirmation on write-protected files. Adding -f (force) skips those confirmation prompts entirely, so rm -rf removes a directory tree unconditionally and permanently — there is no recycle bin, so a mistyped path with -rf cannot be undone.

What is the difference between cat and less for viewing a file?

cat prints a file's entire contents to the terminal at once, which is fine for short files but floods the screen for large ones. less opens the file page by page, letting you scroll with arrow keys, search with /, and quit with q — the better choice for long log files or man pages.

What does chmod +x actually change, and when do you need it?

chmod +x adds execute permission to a file for its permission classes, which is required before you can run a script directly (e.g. ./deploy.sh) rather than passing it to an interpreter (bash deploy.sh). Without execute permission, attempting to run the file directly returns a "Permission denied" error even if you can read its contents.

What is the difference between the pipe (|) operator and the > redirect?

The pipe | sends the standard output of one command directly into the standard input of the next command, chaining them together (e.g. ps aux | grep node). The > operator instead redirects a command's output into a file, overwriting whatever was there — while >> appends to the file instead of overwriting it.

What is the difference between kill and kill -9?

A plain kill <pid> sends SIGTERM, a graceful termination signal the process can catch and use to clean up (close file handles, flush data) before exiting. kill -9 <pid> sends SIGKILL, which the operating system enforces immediately and the process cannot intercept or ignore — useful when a process is hung, but it skips any cleanup the process would otherwise have done.

Why does scp need SSH access to work?

scp (Secure Copy Protocol) copies files between machines by tunneling the transfer over an existing SSH connection, reusing the same authentication (keys or password) and encryption as an interactive ssh session. If you can ssh into a host, you can scp files to and from it using the same credentials.

What is the difference between export and just setting a variable in the shell?

Setting VAR=value in a shell creates a variable visible only to that shell session. Running export VAR=value marks it as an environment variable that child processes — scripts, or programs launched from that shell — inherit automatically. Forgetting export is a common reason a variable a script depends on appears to be "missing" when the script runs.

What does curl -I do differently from a normal curl request?

curl -I sends a HEAD request and prints only the response headers, without downloading the response body — useful for quickly checking a server's status code, content type, or caching headers without transferring the full page or file.

Is this CLI commands reference specific to one shell like bash or zsh?

The commands listed (ls, grep, chmod, curl, ssh, tar, and so on) are standard Unix/Linux utilities available in effectively any POSIX-compatible shell, including bash, zsh, and the Git Bash environment on Windows — the syntax shown works the same regardless of which shell is running them.

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