Linux Basic Commands

Linux Basic Commands

Command	Description
apropos whatis	Show commands pertinent to string. See also threadsafe
man -t ascii | ps2pdf - > ascii.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
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
scp -c arcfour $USER@$LANHOST: bigfile	Use faster crypto for local LAN. This might saturate GigE
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
ssh-copy-id $USER@$HOST	Install public key for $USER@$HOST for password-less log in
wget (multi purpose download tool)
(cd dir/ && 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
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 '1000{p;q}'	Print 1000th line
sed -n '10,20p;20q'	Print lines 10 to 20
sed -n 's/.*<\/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
tr -s '[:blank:]' '\t'	cut fields separated by blanks
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 -t'\0' -a1 -a2 file1 file2	Union of sorted files
join -t'\0' file1 file2	Intersection of sorted files
join -t'\0' -v2 file1 file2	Difference of sorted files
join -t'\0' -v1 -v2 file1 file2	Symmetric Difference of sorted files
math
echo '(1 + sqrt(5))/2' | bc -l	Quick math (Calculate φ). See also bc
seq -f '4/%g' 1 2 99999 | paste -sd-+ | bc -l	Calculate π the unix way
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/9.58s' '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 '12:00 +1 day' +%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)
date --date='TZ="America/Los_Angeles" 09:00 next Fri'	What's the local time for 9AM next Friday on west coast US
locales
printf "%'d\n" 1234	Print number with thousands grouping appropriate to locale
BLOCK_SIZE=\'1 ls -l	Use locale thousands grouping in ls. See also l
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 -kc $(locale | sed -n 's/\(LC_.\{4,\}\)=.*/\1/p') | 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.qp > file.txt	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 -pad *.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
du -hs /home/* | sort -k1,1h	Sort paths by easy to interpret disk usage
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
> file	truncate data of file or create an empty file
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
strace -f -e trace=write -e write=1,2 ls >/dev/null	Monitor what's written to stdout and stderr
ltrace -f -e getenv ls >/dev/null	List library calls made by command
lsof -p $$	List paths that process id has open
lsof ~	List processes that have specified path open
tcpdump not port 22	Show network traffic except ssh. See also tcpdump_not_me
ps -e -o pid,args --forest	List processes in a hierarchy
ps -e -o pcpu,cpu,nice,state,cputime,args --sort pcpu | sed '/^ 0.0 /d'	List processes by % cpu usage
ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS	List processes by mem (KB) usage. See also ps_mem.py
ps -C firefox-bin -L -o pid,tid,pcpu,state	List all threads for a particular process
ps -p 1,$$ -o etime=	List elapsed wall time 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
udevadm monitor	Monitor udev events to help configure rules
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 .	open a file or url with the registered desktop application