Unix Commands

Command List

General Commands

Command Description
apropos word Show commands pertinent to word.
which command Show full path name of command
time command See how long a command takes
time cat Start stopwatch. Ctrl-D to stop.
nice info Run a low priority command (info in this case)
renice 19 -p $$ Make shell (script) low priority. Use for non interactive tasks
look prefix Quickly search (sorted) dictionary
gpg -c file Encrypt file
gpg file.gpg Decrypt file
watch -n1 'cat /proc/interrupts' Watch changeable data continuously
alias hd='od -Ax -tx1z -v' Handy hexdump
alias rp='readlink -f' Canonicalize path.
touch -c -t 0304050607 file Set file timestamp (YYMMDDhhmm)

Directory Navigation

Command Description
cd - Go to previous directory
cd Go to home directory
(cd dir && command) cd, execute a command and return
pushd . Put current dir on stack so you can popd back to it

CD Commands

Command Description
gzip < /dev/cdrom > cdrom.iso.gz Save copy of data cdrom
mount -o loop cdrom.iso /mnt/dir Mount the cdrom image at /mnt/dir (read only)


Command Description

tar -c dir/ | bzip2 > dir.tar.bz2

Make 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/hda | gzip | ssh user@remote 'dd of=hda.gz'

Backup harddisk to remote machine


Command Description

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

File Searching

Command Description

alias l='ls -l --color=auto'

quick dir listing

ls -lrt

List files by date. See also newest

find -name '*.[ch]' | xargs grep -E 'expr'

Search 'expr' in this dir and below.

find -type f -print0 | xargs -r0 grep -F 'string'

Search all regular files for 'string' in this dir and below

find -maxdepth 1 -type f | xargs grep -F 'string'

Search all regular files for 'string' in this dir

find -maxdepth 1 -type f | xargs grep -F 'string'

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


Command Description

ip link show

List interfaces

ethtool interface

List interface status

ip link set dev eth0 name wan

Rename eth0 to wan

ip addr add brd + dev eth0

Add ip and mask(

ip link set dev interface up

Bring interface up (or down)

ip route add default via

Set default gateway to

host pixelbeat.org

Lookup ip address for name or vice versa

hostname -i

Lookup local ip address (equivalent to host hostname)

netstat -tupl

List internet services on a system

netstat -tup

List active connections to/from system

Wget (download tool)

Command Description

(cd cmdline && 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/

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)

Windows (samba)

Command Description


Find windows machines. See also findsmb

nmblookup -A

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)


Command Description

echo '(1 + sqrt(5))/2' | bc -l

Quick math

echo 'obase=16; ibase=10; 123' | bc

Base conversion (decimal to hexadecimal)

echo $((0x2dec))

Base conversion (hex to dec) ((shell arithmetic expansion))

echo 'pad=20; min=64; (10010^6)/((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] (100106)/((pad+x)8)' | gnuplot -persist

Plot FastE packet rate vs packet size

String foo

Command Description

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

sed -n '1000p;1000q'

Print 1000th line

sed -n '10,20p;20q'

Print lines 10 to 20

sort file1 file1 file2 | uniq -u

Show lines in file2 not in file1

echo 'Test' | tr '[:lower:]' '[:upper:]'

Case conversion

tr -dc '[:print:]' < /dev/urandom

Filter non printable characters

grep 'processor' /proc/cpuinfo | wc -l

Count lines


Command Description

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.

date --date='25 Dec' +%A

What day does xmas fall on, this year

date --date '1970-01-01 UTC 1234567890 seconds'

Convert number of seconds since the epoch to a date

TZ=':America/Los_Angeles' date

What time is it on West coast of US (use tzselect to find TZ)


Command Description

printf "%'d\n" 1234

Print number with thousands grouping appropriate to locale

echo "I live in locale territory"

Extract info from locale database

locale | cut -d= -f1 | xargs locale -kc | less

List fields in locale database

LANG=en_IE.utf8 locale int_prefix

Lookup locale info for specific country. See also ccodes

Disk Space

Command Description

ls -lSr

Show files, biggest last

du -s * | sort -k1,1rn | head

Show top disk users in current dir.

df -h

Show free disk space

df -i

Show free inodes

fdisk -l

Show disks partitions sizes and types (run as root)

rpm -q -a --queryformat '%10{SIZE}\t%{NAME}\n' | sort -k1,1n

List all packages by installed size (Bytes) on rpm distros

dpkg-query -W --showformat='${Installed-Size;10}\t${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)

Monitoring / Debugging

Command Description

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 ~

tcpdump not port 22

Show network traffic except ssh.

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 -o rss=,args= | sort -b -k1,1n | pr -TW$COLUMNS

List processes by mem usage.

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

for wtmp in ls -t /var/log/wtmp*; do last reboot -f $wtmp; done | grep reboot

Show system reboot history.

free -m

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

System Info

Command Description

hdparm -i /dev/hda

Show info about disk hda

hdparm -tT /dev/hda

Do a read speed test on disk hda

badblocks -s /dev/hda

Test for unreadable blocks on disk hda

mount | column -t

Show mounted filesystems on the system (and align output)

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

Recode (Obsoletes iconv, dos2unix, unix2dos)

Command Description

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


Command Description


Powerful filemanager that can browse rpm, tar, ftp, ssh, ...


Virtual terminals with detach capability, ...


Web browser


Interactive/scriptable graphing


Matlab like environment

Useful Commands

Dumping a mySQL to a sql file

mysqldump -l --opt databasename > /root/file/location/filename.sql  -u user --password=whateverthepass

Importing mySQL dump file

mysql databasename < /root/file/location/filename.sql -u user --password=whateverthepass

Copying Entire Folder of Files

cp - Ru /root/file/location/* /where/it/should/go --reply=yes

Copying an entire folder to another server

tar zcf - localfolder/ \ | ssh "cd folder/to/copy/to; tar zpxvf -"

If you want to extract one file from the .tar.gz file use

gzip -dc file.tar.gz | tar xf - pathname/filename

The pathname and filename should be exactly as given in the .tar.gz file. If you want more than one file append their names, again include pathname, at the end of the command.

Symlinking (Source --> Location)

ln -s /source/foldername /folder/where/symlink/will/be