Classical shell commands

Here is a brief definition of classical and useful Linux commands.

There is an extended version of this page here.

General

man

interface to the reference manuals

tldr

modern days man (online collection of community-maintained help pages, simpler complement to traditional man pages.)

history

command-line history (display the commands history list with line numbers)

Files

cd

change current (working) directory

ls

list directory contents

pwd

print name of current/working directory (where am I ?)

chmod

change file rights

find

search for files in a directory hierarchy

grep

print lines matching a pattern (see also : pcregrep, ripgrep)

less

Open a file for interactive reading, allowing scrolling and search.

cat

print file on the standard output (and concatenate files)

tail

output the last part (last N lines) of files (NB: tail -f)

head

output the first part (first N lines) of files

du

disk usage (estimate file space usage)

df

gives an overview of the filesystem disk space usage

which

locate a command/program in the user’s path

Process

top / htop

display live current system state (tasks) / modern version of top

ps

report a snapshot of the current processes

kill

send a signal to a process (usually to kill/stop it)

Other useful commands without an explanation ()

Use tldr to learn usage and commonly used options

• cp, mv, rm, cut, sed

• tar, gzip/gunzip

• ip, ping, wget/curl