Linux command line reference

This is a Linux command line reference for common operations. Examples marked with • are valid/safe to paste without modification into a terminal, so you may want to keep a terminal window open while reading this so you can cut & paste.

Commands
•apropos whatis
Show commands pertinent to string. See also threadsafe

•man -t man | ps2pdf - > man.pdf
make a pdf of a manual page

which command
Show full path name of command

time command
See how long a command takes

•time cat
Start stopwatch. Ctrl-d to stop. See also sw

•nice info
Run a low priority command (The "info" reader in this case)

•renice 19 -p $$
Make shell (script) low priority. Use for non interactive tasks

dir navigation

•cd -
Go to previous directory

•cd
Go to $HOME directory

(cd dir && command)
Go to dir, execute command and return to current dir

•pushd .
Put current dir on stack so you can popd back to it

file searching

•alias l='ls -l --color=auto'
quick dir listing

•ls -lrt
List files by date. See also newest and find_mm_yyyy

•ls /usr/bin | pr -T9 -W$COLUMNS
Print in 9 columns to width of terminal

find -name '*.[ch]' | xargs grep -E 'expr'
Search 'expr' in this dir and below. See also findrepo

find -type f -print0 | xargs -r0 grep -F 'example'
Search all regular files for 'example' in this dir and below

find -maxdepth 1 -type f | xargs grep -F 'example'
Search all regular files for 'example' in this dir

find -maxdepth 1 -type d | while read dir; do echo $dir; echo cmd2; done
Process each item with multiple commands (in while loop)

•find -type f ! -perm -444
Find files not readable by all (useful for web site)

•find -type d ! -perm -111
Find dirs not accessible by all (useful for web site)

•locate -r 'file[^/]*\.txt'
Search cached index for names. This re is like glob *file*.txt

•look reference
Quickly search (sorted) dictionary for prefix

•grep --color reference /usr/share/dict/words
Highlight occurances of regular expression in dictionary

archives and compression

gpg -c file
Encrypt file

gpg file.gpg
Decrypt file

tar -c dir/ | bzip2 > dir.tar.bz2
Make compressed archive of dir/

bzip2 -dc dir.tar.bz2 | tar -x
Extract archive (use gzip instead of bzip2 for tar.gz files)

tar -c dir/ | gzip | gpg -c | ssh user@remote 'dd of=dir.tar.gz.gpg'
Make encrypted archive of dir/ on remote machine

find dir/ -name '*.txt' | tar -c --files-from=- | bzip2 > dir_txt.tar.bz2
Make archive of subset of dir/ and below

find dir/ -name '*.txt' | xargs cp -a --target-directory=dir_txt/ --parents
Make copy of subset of dir/ and below

( tar -c /dir/to/copy ) | ( cd /where/to/ && tar -x -p )
Copy (with permissions) copy/ dir to /where/to/ dir

( cd /dir/to/copy && tar -c . ) | ( cd /where/to/ && tar -x -p )
Copy (with permissions) contents of copy/ dir to /where/to/

( tar -c /dir/to/copy ) | ssh -C user@remote 'cd /where/to/ && tar -x -p'
Copy (with permissions) copy/ dir to remote:/where/to/ dir

dd bs=1M if=/dev/sda | gzip | ssh user@remote 'dd of=sda.gz'
Backup harddisk to remote machine

rsync (Network efficient file copier: Use the --dry-run option for testing)

rsync -P rsync://rsync.server.com/path/to/file file
Only get diffs. Do multiple times for troublesome downloads

rsync --bwlimit=1000 fromfile tofile
Locally copy with rate limit. It's like nice for I/O

rsync -az -e ssh --delete ~/public_html/ remote.com:'~/public_html'
Mirror web site (using compression and encryption)

rsync -auz -e ssh remote:/dir/ . && rsync -auz -e ssh . remote:/dir/
Synchronize current directory with remote one

ssh (Secure SHell)

ssh $USER@$HOST command
Run command on $HOST as $USER (default command=shell)

•ssh -f -Y $USER@$HOSTNAME xeyes
Run GUI command on $HOSTNAME as $USER

scp -p -r $USER@$HOST: file dir/
Copy with permissions to $USER's home directory on $HOST

ssh -g -L 8080:localhost:80 root@$HOST
Forward connections to $HOSTNAME:8080 out to $HOST:80

ssh -R 1434:imap:143 root@$HOST
Forward connections from $HOST:1434 in to imap:143

wget (multi purpose download tool)

•(cd cli && wget -nd -pHEKk http://www.pixelbeat.org/cmdline.html)
Store local browsable version of a page to the current dir

wget -c http://www.example.com/large.file
Continue downloading a partially downloaded file

wget -r -nd -np -l1 -A '*.jpg' http://www.example.com/dir/
Download a set of files to the current directory

wget ftp://remote/file[1-9].iso/
FTP supports globbing directly

•wget -q -O- http://www.pixelbeat.org/timeline.html | grep 'a href' | head
Process output directly

echo 'wget url' | at 01:00
Download url at 1AM to current dir

wget --limit-rate=20k url
Do a low priority download (limit to 20KB/s in this case)

wget -nv --spider --force-html -i bookmarks.html
Check links in a file

wget --mirror http://www.example.com/
Efficiently update a local copy of a site (handy from cron)

networking (Note ifconfig, route, mii-tool, nslookup commands are obsolete)

ethtool eth0
Show status of ethernet interface eth0

ethtool --change eth0 autoneg off speed 100 duplex full
Manually set ethernet interface speed

iwconfig eth1
Show status of wireless interface eth1

iwconfig eth1 rate 1Mb/s fixed
Manually set wireless interface speed

•iwlist scan
List wireless networks in range

•ip link show
List network interfaces

ip link set dev eth0 name wan
Rename interface eth0 to wan

ip link set dev eth0 up
Bring interface eth0 up (or down)

•ip addr show
List addresses for interfaces

ip addr add 1.2.3.4/24 brd + dev eth0
Add (or del) ip and mask (255.255.255.0)

•ip route show
List routing table

ip route add default via 1.2.3.254
Set default gateway to 1.2.3.254

•tc qdisc add dev lo root handle 1:0 netem delay 20msec
Add 20ms latency to loopback device (for testing)

•tc qdisc del dev lo root
Remove latency added above

•host pixelbeat.org
Lookup DNS ip address for name or vice versa

•hostname -i
Lookup local ip address (equivalent to host `hostname`)

•whois pixelbeat.org
Lookup whois info for hostname or ip address

•netstat -tupl
List internet services on a system

•netstat -tup
List active connections to/from system

windows networking (Note samba is the package that provides all this windows specific networking support)

•smbtree
Find windows machines. See also findsmb

nmblookup -A 1.2.3.4
Find the windows (netbios) name associated with ip address

smbclient -L windows_box
List shares on windows machine or samba server

mount -t smbfs -o fmask=666,guest //windows_box/share /mnt/share
Mount a windows share

echo 'message' | smbclient -M windows_box
Send popup to windows machine (off by default in XP sp2)

text manipulation (Note sed uses stdin and stdout. Newer versions support inplace editing with the -i option)

sed 's/string1/string2/g'
Replace string1 with string2

sed 's/\(.*\)1/\12/g'
Modify anystring1 to anystring2

sed '/ *#/d; /^ *$/d'
Remove comments and blank lines

sed ':a; /\\$/N; s/\\\n//; ta'
Concatenate lines with trailing \

sed 's/[ \t]*$//'
Remove trailing spaces from lines

sed 's/\([\\`\\"$\\\\]\)/\\\1/g'
Escape shell metacharacters active within double quotes

•seq 10 | sed "s/^/      /; s/ *\(.\{7,\}\)/\1/"
Right align numbers

sed -n '1000p;1000q'
Print 1000th line

sed -n '10,20p;20q'
Print lines 10 to 20

sed -n 's/.*<title>\(.*\)<\/title>.*/\1/ip;T;q'
Extract title from HTML web page

sed -i 42d ~/.ssh/known_hosts
Delete a particular line

sort -t. -k1,1n -k2,2n -k3,3n -k4,4n
Sort IPV4 ip addresses

•echo 'Test' | tr '[:lower:]' '[:upper:]'
Case conversion

•tr -dc '[:print:]' < /dev/urandom
Filter non printable characters

•history | wc -l
Count lines

set operations (Note you can export LANG=C for speed. Also these assume no duplicate lines within a file)

sort file1 file2 | uniq
Union of unsorted files

sort file1 file2 | uniq -d
Intersection of unsorted files

sort file1 file1 file2 | uniq -u
Difference of unsorted files

sort file1 file2 | uniq -u
Symmetric Difference of unsorted files

join -a1 -a2 file1 file2
Union of sorted files

join file1 file2
Intersection of sorted files

join -v2 file1 file2
Difference of sorted files

join -v1 -v2 file1 file2
Symmetric Difference of sorted files

math

•echo '(1 + sqrt(5))/2' | bc -l
Quick math (Calculate φ). See also bc

•echo 'pad=20; min=64; (100*10^6)/((pad+min)*8)' | bc
More complex (int) e.g. This shows max FastE packet rate

•echo 'pad=20; min=64; print (100E6)/((pad+min)*8)' | python
Python handles scientific notation

•echo 'pad=20; plot [64:1518] (100*10**6)/((pad+x)*8)' | gnuplot -persist
Plot FastE packet rate vs packet size

•echo 'obase=16; ibase=10; 64206' | bc
Base conversion (decimal to hexadecimal)

•echo $((0x2dec))
Base conversion (hex to dec) ((shell arithmetic expansion))

•units -t '100m/9.69s' 'miles/hour'
Unit conversion (metric to imperial)

•units -t '500GB' 'GiB'
Unit conversion (SI to IEC prefixes)

•units -t '1 googol'
Definition lookup

•seq 100 | (tr '\n' +; echo 0) | bc
Add a column of numbers. See also add and funcpy

calendar

•cal -3
Display a calendar

•cal 9 1752
Display a calendar for a particular month year

•date -d fri
What date is it this friday. See also day

•[ $(date -d "tomorrow" +%d) = "01" ] || exit
exit a script unless it's the last day of the month

•date --date='25 Dec' +%A
What day does xmas fall on, this year

•date --date='@2147483647'
Convert seconds since the epoch (1970-01-01 UTC) to date

•TZ=':America/Los_Angeles' date
What time is it on West coast of US (use tzselect to find TZ)

echo "mail -s 'get the train' P@draigBrady.com < /dev/null" | at 17:45
Email reminder

•echo "DISPLAY=$DISPLAY xmessage cooker" | at "NOW + 30 minutes"
Popup reminder

locales

•printf "%'d\n" 1234
Print number with thousands grouping appropriate to locale

•BLOCK_SIZE=\'1 ls -l
get ls to do thousands grouping appropriate to locale

•echo "I live in `locale territory`"
Extract info from locale database

•LANG=en_IE.utf8 locale int_prefix
Lookup locale info for specific country. See also ccodes

•locale | cut -d= -f1 | xargs locale -kc | less
List fields available in locale database

recode (Obsoletes iconv, dos2unix, unix2dos)

•recode -l | less
Show available conversions (aliases on each line)

recode windows-1252.. file_to_change.txt
Windows "ansi" to local charset (auto does CRLF conversion)

recode utf-8/CRLF.. file_to_change.txt
Windows utf8 to local charset

recode iso-8859-15..utf8 file_to_change.txt
Latin9 (western europe) to utf8

recode ../b64 < file.txt > file.b64
Base64 encode

recode /qp.. < file.txt > file.qp
Quoted printable decode

recode ..HTML < file.txt > file.html
Text to HTML

•recode -lf windows-1252 | grep euro
Lookup table of characters

•echo -n 0x80 | recode latin-9/x1..dump
Show what a code represents in latin-9 charmap

•echo -n 0x20AC | recode ucs-2/x2..latin-9/x
Show latin-9 encoding

•echo -n 0x20AC | recode ucs-2/x2..utf-8/x
Show utf-8 encoding

CDs

gzip < /dev/cdrom > cdrom.iso.gz
Save copy of data cdrom

mkisofs -V LABEL -r dir | gzip > cdrom.iso.gz
Create cdrom image from contents of dir

mount -o loop cdrom.iso /mnt/dir
Mount the cdrom image at /mnt/dir (read only)

cdrecord -v dev=/dev/cdrom blank=fast
Clear a CDRW

gzip -dc cdrom.iso.gz | cdrecord -v dev=/dev/cdrom -
Burn cdrom image (use dev=ATAPI -scanbus to confirm dev)

cdparanoia -B
Rip audio tracks from CD to wav files in current dir

cdrecord -v dev=/dev/cdrom -audio *.wav
Make audio CD from all wavs in current dir (see also cdrdao)

oggenc --tracknum='track' track.cdda.wav -o 'track.ogg'
Make ogg file from wav file

disk space (See also FSlint)

•ls -lSr
Show files by size, biggest last

•du -s * | sort -k1,1rn | head
Show top disk users in current dir. See also dutop

•df -h
Show free space on mounted filesystems

•df -i
Show free inodes on mounted filesystems

•fdisk -l
Show disks partitions sizes and types (run as root)

•rpm -q -a --qf '%10{SIZE}\t%{NAME}\n' | sort -k1,1n
List all packages by installed size (Bytes) on rpm distros

•dpkg-query -W -f='${Installed-Size;10}\t${Package}\n' | sort -k1,1n
List all packages by installed size (KBytes) on deb distros

•dd bs=1 seek=2TB if=/dev/null of=ext3.test
Create a large test file (taking no space). See also truncate

monitoring/debugging

•tail -f /var/log/messages
Monitor messages in a log file

•strace -c ls >/dev/null
Summarise/profile system calls made by command

•strace -f -e open ls >/dev/null
List system calls made by command

•ltrace -f -e getenv ls >/dev/null
List library calls made by command

•lsof -p $$
List paths that process id has open

•lsof ~
List processes that have specified path open

•tcpdump not port 22
Show network traffic except ssh. See also tcpdump_not_me

•ps -e -o pid,args --forest
List processes in a hierarchy

•ps -e -o pcpu,cpu,nice,state,cputime,args --sort pcpu | sed '/^ 0.0 /d'
List processes by % cpu usage

•ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS
List processes by mem usage. See also ps_mem.py

•ps -C firefox-bin -L -o pid,tid,pcpu,state
List all threads for a particular process

•ps -p 1,2
List info for particular process IDs

•last reboot
Show system reboot history

•free -m
Show amount of (remaining) RAM (-m displays in MB)

•watch -n.1 'cat /proc/interrupts'
Watch changeable data continuously

system information (see also sysinfo) ('#' means root access is required)

•uname -a
Show kernel version and system architecture

•head -n1 /etc/issue
Show name and version of distribution

•cat /proc/partitions
Show all partitions registered on the system

•grep MemTotal /proc/meminfo
Show RAM total seen by the system

•grep "model name" /proc/cpuinfo
Show CPU(s) info

•lspci -tv
Show PCI info

•lsusb -tv
Show USB info

•mount | column -t
List mounted filesystems on the system (and align output)

•grep -F capacity: /proc/acpi/battery/BAT0/info
Show state of cells in laptop battery

#dmidecode -q | less
Display SMBIOS/DMI information

#smartctl -A /dev/sda | grep Power_On_Hours
How long has this disk (system) been powered on in total

#hdparm -i /dev/sda
Show info about disk sda

#hdparm -tT /dev/sda
Do a read speed test on disk sda

#badblocks -s /dev/sda
Test for unreadable blocks on disk sda

interactive (see also linux keyboard shortcuts)

•readline
Line editor used by bash, python, bc, gnuplot, ...

•screen
Virtual terminals with detach capability, ...

•mc
Powerful file manager that can browse rpm, tar, ftp, ssh, ...

•gnuplot
Interactive/scriptable graphing

•links
Web browser

•xdg-open http://www.pixelbeat.org/
open a file or url with the registered desktop application

miscellaneous

•alias hd='od -Ax -tx1z -v'
Handy hexdump. (usage e.g.: • hd /proc/self/cmdline | less)

•alias realpath='readlink -f'
Canonicalize path. (usage e.g.: • realpath ~/../$USER)

•set | grep $USER
Search current environment

touch -c -t 0304050607 file
Set file timestamp (YYMMDDhhmm)

•python -m SimpleHTTPServer
Serve current directory tree at http://$HOSTNAME:8000/