Linux

Bash / Shell

Everyday bash commands for navigation, file operations, process management and scripting.

Navigation & Files

ls -lahList with details, hidden files, human-readable sizes

cd -Switch to previous directory

pwdPrint working directory

mkdir -p path/to/dirCreate nested directories

cp -r src/ dst/Copy directory recursively

mv src dstMove or rename a file/directory

rm -rf <dir>Remove directory and contents recursively

ln -s target linkCreate a symbolic link

find . -name "*.log"Find files by name pattern

find . -type f -mtime -1Files modified in the last day

Permissions

chmod 755 <file>rwxr-xr-x (owner full, others read/exec)

chmod +x <file>Make file executable

chown user:group <file>Change owner and group

chown -R user:group <dir>Recursively change ownership

umask 022Set default permission mask for new files

Text & Files

less <file>Page through a file

tail -f <file>Follow a file as it grows

head -n 20 <file>Show first 20 lines

wc -l <file>Count lines in a file

sort file.txtSort lines alphabetically

sort -rn file.txtSort numerically in reverse

uniqRemove consecutive duplicate lines

cut -d',' -f1 file.csvExtract first field by delimiter

diff file1 file2Show differences between two files

Process Management

ps auxList all running processes

kill <pid>Send SIGTERM to a process

kill -9 <pid>Force-kill a process (SIGKILL)

pkill <name>Kill processes by name

jobsList background jobs in current shell

Ctrl+zSuspend current foreground process

bg %1Resume job 1 in background

fg %1Bring job 1 to foreground

nohup <cmd> &Run command immune to terminal hangup

Variables & Scripting

VAR=valueAssign a variable (no spaces around =)

export VAR=valueExport variable to child processes

$?Exit code of last command

$0 / $1 / $#Script name / first arg / number of args

$@All positional arguments as separate words

[ -f file ]Test if file exists and is a regular file

[ -d dir ]Test if directory exists

[ -z "$VAR" ]Test if variable is empty

Redirection & Pipes

cmd > fileRedirect stdout to file (overwrite)

cmd >> fileAppend stdout to file

cmd 2>&1Redirect stderr to stdout

cmd &> fileRedirect both stdout and stderr to file

cmd1 | cmd2Pipe stdout of cmd1 to stdin of cmd2

cmd < fileRead stdin from file

tee fileWrite to file and also pass through stdout

cmd 2>/dev/nullSuppress stderr

Networking

ss -tlnpShow listening TCP sockets with processes

nc -zv host 443Test TCP connectivity to a port

dig <domain>DNS lookup

ping -c 4 <host>Send 4 ICMP pings

traceroute <host>Trace network path to host

ip addr showShow network interfaces and IPs