Ruprecht-Karls-Universität Heidelberg

Sophisticated Commands

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. All these commands have been tested both on Fedora and Ubuntu.


CommandDescription
apropos whatisShow commands pertinent to string.
man -t man | ps2pdf - > man.pdfmake a pdf of a manual page
 which commandShow full path name of command
 time commandSee how long a command takes
time catStart stopwatch. Ctrl-d to stop.
nice infoRun 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
cdGo to $HOME directory
 (cd dir && command)Go to dir, execute command and return to current dir
pushd .Put current dir on stack so you can popd back to it
alias l='ls -l --color=auto'quick dir listing
ls -lrtList files by date.
ls /usr/bin | pr -T9 -W$COLUMNSPrint in 9 columns to width of terminal
 find -name '*.[ch]' | xargs grep -E 'expr'Search 'expr' in this dir and below. </tr>
 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; doneProcess each item with multiple commands (in while loop)
find -type f ! -perm -444Find files not readable by all (useful for web site)
find -type d ! -perm -111Find 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 referenceQuickly search (sorted) dictionary for prefix
grep --color reference /usr/share/dict/wordsHighlight occurances of regular expression in dictionary
archives and compression
 gpg -c fileEncrypt file
 gpg file.gpgDecrypt file
 tar -c dir/ | bzip2 > dir.tar.bz2Make compressed archive of dir/
 bzip2 -dc dir.tar.bz2 | tar -xExtract 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.bz2Make archive of subset of dir/ and below
 find dir/ -name '*.txt' | xargs cp -a --target-directory=dir_txt/ --parentsMake 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 (Use the --dry-run option for testing)
 rsync -P rsync://rsync.server.com/path/to/file fileOnly get diffs. Do multiple times for troublesome downloads
 rsync --bwlimit=1000 fromfile tofileLocally 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 commandRun command on $HOST as $USER (default command=shell)
ssh -f -Y $USER@$HOSTNAME xeyesRun GUI command on $HOSTNAME as $USER
 scp -p -r $USER@$HOST: file dir/Copy with permissions to $USER's home directory on $HOST
 ssh -g -L 8080:localhost:80 root@$HOSTForward connections to $HOSTNAME:8080 out to $HOST:80
 ssh -R 1434:imap:143 root@$HOSTForward 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.fileContinue 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' | headProcess output directly
 echo 'wget url' | at 01:00Download url at 1AM to current dir
 wget --limit-rate=20k urlDo a low priority download (limit to 20 KB/s in this case)
 wget -nv --spider --force-html -i bookmarks.htmlCheck 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 eth0Show status of ethernet interface eth0
 ethtool --change eth0 autoneg off speed 100 duplex fullManually set ethernet interface speed
 iwconfig eth1Show status of wireless interface eth1
 iwconfig eth1 rate 1Mb/s fixedManually set wireless interface speed
iwlist scanList wireless networks in range
ip link showList network interfaces
 ip link set dev eth0 name wanRename interface eth0 to wan
 ip link set dev eth0 upBring interface eth0 up (or down)
ip addr showList addresses for interfaces
 ip addr add 1.2.3.4/24 brd + dev eth0Add (or del) ip and mask (255.255.255.0)
ip route showList routing table
 ip route add default via 1.2.3.254Set default gateway to 1.2.3.254
tc qdisc add dev lo root handle 1:0 netem delay 20msecAdd 20ms latency to loopback device (for testing)
tc qdisc del dev lo rootRemove latency added above
host pixelbeat.orgLookup DNS ip address for name or vice versa
hostname -iLookup local ip address (equivalent to host `hostname`)
whois pixelbeat.orgLookup whois info for hostname or ip address
netstat -tuplList internet services on a system
netstat -tupList active connections to/from system
windows networking (Note samba is the package that provides all this windows specific networking support)
smbtreeFind windows machines. See also findsmb
 nmblookup -A 1.2.3.4Find the windows (netbios) name associated with ip address
 smbclient -L windows_boxList shares on windows machine or samba server
 mount -t smbfs -o fmask=666,guest //windows_box/share /mnt/shareMount a windows share
 echo 'message' | smbclient -M windows_boxSend popup to windows machine (off by default in XP sp2)
text manipulation (Note sed uses stdin and stdout, so if you want to edit files, append <oldfile >newfile)
 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;<acronym title="quit ASAP">1000q</acronym>'Print 1000th line
 sed -n '10,20p;<acronym title="quit ASAP">20q</acronym>'Print lines 10 to 20
 sed -n 's/.*<title>\(.*\)<\/title>.*/\1/ip;<acronym title="quit after match">T;q</acronym>'Extract title from HTML web page
 sort -t. -k1,1n -k2,2n -k3,3n -k4,4nSort IPV4 ip addresses
echo 'Test' | tr '[:lower:]' '[:upper:]'Case conversion
tr -dc '[:print:]' < /dev/urandomFilter non printable characters
history | wc -lCount lines
sort operations (Note you can export LANG=C for speed. Also these assume no duplicate lines within a file)
 sort file1 file2 | uniqUnion of unsorted files
 sort file1 file2 | uniq -dIntersection of unsorted files
 sort file1 file1 file2 | uniq -uDifference of unsorted files
 sort file1 file2 | uniq -uSymmetric Difference of unsorted files
 join -a1 -a2 file1 file2Union of sorted files
 join file1 file2Intersection of sorted files
 join -v2 file1 file2Difference of sorted files
 join -v1 -v2 file1 file2Symmetric Difference of sorted files
math
echo '(1 + sqrt(5))/2' | bc -lQuick math (Calculate ?).
echo 'pad=20; min=64; (100*10^6)/((pad+min)*8)' | bcMore complex (int) e.g. This shows max FastE packet rate
echo 'pad=20; min=64; print (100E6)/((pad+min)*8)' | pythonPython handles scientific notation
echo 'pad=20; plot [64:1518] (100*10**6)/((pad+x)*8)' | gnuplot -persistPlot FastE packet rate vs packet size
echo 'obase=16; ibase=10; 64206' | bcBase conversion (decimal to hexadecimal)
echo $((0x2dec))Base conversion (hex to dec) ((shell arithmetic expansion))
units -t '100m/9.74s' 'miles/hour'Unit conversion (metric to imperial)
units -t '500GB' 'GiB'Unit conversion (SI to IEC prefixes)
units -t '1 googol'Definition lookup
seq 100 | (tr '\n' +; echo 0) | bcAdd a column of numbers.
calendar
cal -3Display a calendar
cal 9 1752Display a calendar for a particular month year
date -d friWhat date is it this friday. See also <a href="scripts/day">day</a>
date --date='25 Dec' +%AWhat day does xmas fall on, this year
date --date '1970-01-01 UTC 2147483647 seconds'Convert number of seconds since the epoch to a date
TZ=':America/Los_Angeles' dateWhat time is it on West coast of US (use tzselect to find TZ)
 echo "mail -s 'get the train' P@draigBrady.com < /dev/null" | at 17:45Email reminder
echo "DISPLAY=$DISPLAY xmessage cooker" | at "NOW + 30 minutes"Popup reminder
locales
printf "%'d\n" 1234Print number with thousands grouping appropriate to locale
BLOCK_SIZE=\'1 ls -lget 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_prefixLookup locale info for specific country.
locale | cut -d= -f1 | xargs locale -kc | lessList fields available in locale database
recode (Obsoletes iconv, dos2unix, unix2dos)
recode -l | lessShow available conversions (aliases on each line)
 recode windows-1252.. file_to_change.txtWindows "ansi" to local charset (auto does CRLF conversion)
 recode utf-8/CRLF.. file_to_change.txtWindows utf8 to local charset
 recode iso-8859-15..utf8 file_to_change.txtLatin9 (western europe) to utf8
 recode ../b64 < file.txt > file.b64Base64 encode
 recode /qp.. < file.txt > file.qpQuoted printable decode
 recode ..HTML < file.txt > file.htmlText to HTML
recode -lf windows-1252 | grep euroLookup table of characters
echo -n 0x80 | recode latin-9/x1..dumpShow what a code represents in latin-9 charmap
echo -n 0x20AC | recode ucs-2/x2..latin-9/xShow latin-9 encoding
echo -n 0x20AC | recode ucs-2/x2..utf-8/xShow utf-8 encoding
CDs
 gzip /dev/cdrom; cdrom.iso.gzSave copy of data cdrom
 mkisofs -V LABEL -r dir | gzip > cdrom.iso.gzCreate cdrom image from contents of dir
 mount -o loop cdrom.iso /mnt/dirMount the cdrom image at /mnt/dir (read only)
 cdrecord -v dev=/dev/cdrom blank=fastClear a CDRW
 gzip -dc cdrom.iso.gz | cdrecord -v dev=/dev/cdrom -Burn cdrom image (use dev=ATAPI -scanbus to confirm dev)
 cdparanoia -BRip audio tracks from CD to wav files in current dir
 cdrecord -v dev=/dev/cdrom -audio *.wavMake 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
ls -lSrShow files by size, biggest last
du -s * | sort -k1,1rn | headShow top disk users in current dir.
df -hShow free space on mounted filesystems
df -iShow free inodes on mounted filesystems
fdisk -lShow disks partitions sizes and types (run as root)
rpm -q -a --qf '%10{SIZE}\t%{NAME}\n' | sort -k1,1nList all packages by installed size (Bytes) on rpm distros
dpkg -query -W -f='${Installed-Size;10}\t${Package}\n' | sort -k1,1nList all packages by installed size (KBytes) on deb distros
dd bs=1 seek=2TB if=/dev/null of=ext3.testCreate a large test file (taking no space).
monitoring/debugging
tail -f /var/log/messagesMonitor messages in a log file
strace -c ls /dev/nullSummarise/profile system calls made by command
strace -f -e open ls >/dev/nullList system calls made by command
ltrace -f -e getenv ls >/dev/nullList 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 22Show network traffic except ssh
ps -e -o pid,args --forestList 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$COLUMNSList processes by mem usage. See also <a href="scripts/ps_mem.py">ps_mem.py</a>
ps -C firefox-bin -L -o pid,tid,pcpu,stateList all threads for a particular process
ps -p 1,2List info for particular process IDs
last rebootShow system reboot history
free -mShow amount of (remaining) RAM (-m displays in MB)
watch -n1 'cat /proc/interrupts'Watch changeable data continuously
system information ('#' means root access is required)
uname -aShow kernel version and system architecture
head -n1 /etc/issueShow name and version of distribution
cat /proc/partitionsShow all partitions registered on the system
grep MemTotal /proc/meminfoShow RAM total seen by the system
grep "model name" /proc/cpuinfoShow CPU(s) info
lspci -tvShow PCI info
lsusb -tvShow USB info
mount | column -tList mounted filesystems on the system (and align output)
#dmidecode -q | lessDisplay SMBIOS/DMI information
#smartctl -A /dev/sda | grep Power_On_HoursHow long has this disk (system) been powered on in total
#hdparm -i /dev/sdaShow info about disk sda
#hdparm -tT /dev/sdaDo a read speed test on disk sda
#badblocks -s /dev/sdaTest for unreadable blocks on disk sda
interactive
readlineLine editor used by bash, python, bc, gnuplot, ...
screenVirtual terminals with detach capability, ...
mcPowerful file manager that can browse rpm, tar, ftp, ssh, ...
gnuplotInteractive/scriptable graphing
miscellaneous
alias hd='od -Ax -tx1z -v'Handy hexdump. (usage e.g.: • hd /proc/self/cmdline | less)
alias realpath='readlink -f'Canonicalize path. (usage e.g.: • realpath ~/../$USER)
set | grep $USERSearch current environment
 touch -c -t 0304050607 fileSet file timestamp (YYMMDDhhmm)
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