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Common Linux CLI Operations

This is a linux command line reference for common operations.

Command Description
• 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:// 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/’~/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 Store local browsable version of a page to the current dir
wget -c Continue downloading a partially downloaded file
wget -r -nd -np -l1 -A ‘*.jpg’ Download a set of files to the current directory
wget ftp://remote/file[1-9].iso/ FTP supports globbing directly
• wget -q -O- | 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 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 brd + dev eth0 Add (or del) ip and mask (
• ip route show List routing table
ip route add default via Set default gateway to
• 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 Lookup DNS ip address for name or vice versa
• hostname -i Lookup local ip address (equivalent to host `hostname`)
• whois 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 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, so if you want to edit files, append 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;1000q’ 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<br /> sort -t. -k1,1n -k2,2n -k3,3n -k4,4n Sort IPV4 ip addresses<br /> • echo ‘Test’ | tr ‘[:lower:]’ ‘[:upper:]’ Case conversion<br /> • 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 $((0x2dec)) Base conversion (hex to dec) ((shell arithmetic expansion)) • units -t '100m/9.72s' 'miles/hour' Unit conversion (metric to imperial) • units -t '500GB' 'GiB' Unit conversion (SI to IEC prefixes) • units -t '1 googol' Definition lookup • seq 100 | (tr 'n' +; echo 0) | bc Add a column of numbers. See also add and funcpy calendar • cal -3 Display a calendar • cal 9 1752 Display a calendar for a particular month year • date -d fri What date is it this friday. See also day • date --date='25 Dec' +%A What day does xmas fall on, this year • date --date='@2147483647' Convert seconds since the epoch (1970-01-01 UTC) to date • TZ=':America/Los_Angeles' date What time is it on West coast of US (use tzselect to find TZ) echo "mail -s 'get the train' < /dev/null" | at 17:45 Email reminder • echo "DISPLAY=$DISPLAY xmessage cooker" | at "NOW + 30 minutes" Popup reminder locales • printf "%'dn" 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<br /> recode /qp.. < file.txt > file.qp Quoted printable decode<br /> recode ..HTML < file.txt > file.html Text to HTML<br /> • recode -lf windows-1252 | grep euro Lookup table of characters<br /> • echo -n 0x80 | recode latin-9/x1..dump Show what a code represents in latin-9 charmap<br /> • echo -n 0x20AC | recode ucs-2/x2..latin-9/x Show latin-9 encoding<br /> • echo -n 0x20AC | recode ucs-2/x2..utf-8/x Show utf-8 encoding<br /> CDs<br /> gzip < /dev/cdrom > cdrom.iso.gz Save copy of data cdrom<br /> mkisofs -V LABEL -r dir | gzip > cdrom.iso.gz Create cdrom image from contents of dir<br /> mount -o loop cdrom.iso /mnt/dir Mount the cdrom image at /mnt/dir (read only)<br /> cdrecord -v dev=/dev/cdrom blank=fast Clear a CDRW<br /> gzip -dc cdrom.iso.gz | cdrecord -v dev=/dev/cdrom – Burn cdrom image (use dev=ATAPI -scanbus to confirm dev)<br /> cdparanoia -B Rip audio tracks from CD to wav files in current dir<br /> cdrecord -v dev=/dev/cdrom -audio *.wav Make audio CD from all wavs in current dir (see also cdrdao)<br /> oggenc –tracknum=’track’ track.cdda.wav -o ‘track.ogg’ Make ogg file from wav file<br /> disk space (See also FSlint)<br /> • ls -lSr Show files by size, biggest last<br /> • du -s * | sort -k1,1rn | head Show top disk users in current dir. See also dutop<br /> • df -h Show free space on mounted filesystems<br /> • df -i Show free inodes on mounted filesystems<br /> • fdisk -l Show disks partitions sizes and types (run as root)<br /> • rpm -q -a –qf ‘%10{SIZE}t%{NAME}n’ | sort -k1,1n List all packages by installed size (Bytes) on rpm distros<br /> • dpkg-query -W -f=’${Installed-Size;10}t${Package}n’ | sort -k1,1n List all packages by installed size (KBytes) on deb distros<br /> • dd bs=1 seek=2TB if=/dev/null of=ext3.test Create a large test file (taking no space). See also truncate<br /> monitoring/debugging<br /> • tail -f /var/log/messages Monitor messages in a log file<br /> • strace -c ls >/dev/null Summarise/profile system calls made by command<br /> • strace -f -e open ls >/dev/null List system calls made by command<br /> • ltrace -f -e getenv ls >/dev/null List library calls made by command<br /> • lsof -p $$ List paths that process id has open<br /> • lsof ~ List processes that have specified path open<br /> • tcpdump not port 22 Show network traffic except ssh. See also tcpdump_not_me<br /> • ps -e -o pid,args –forest List processes in a hierarchy<br /> • ps -e -o pcpu,cpu,nice,state,cputime,args –sort pcpu | sed ‘/^ 0.0 /d’ List processes by % cpu usage<br /> • ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS List processes by mem usage. See also<br /> • ps -C firefox-bin -L -o pid,tid,pcpu,state List all threads for a particular process<br /> • ps -p 1,2 List info for particular process IDs<br /> • last reboot Show system reboot history<br /> • free -m Show amount of (remaining) RAM (-m displays in MB)<br /> • watch -n.1 ‘cat /proc/interrupts’ Watch changeable data continuously<br /> system information (see also sysinfo) (‘#’ means root access is required)<br /> • uname -a Show kernel version and system architecture<br /> • head -n1 /etc/issue Show name and version of distribution<br /> • cat /proc/partitions Show all partitions registered on the system<br /> • grep MemTotal /proc/meminfo Show RAM total seen by the system<br /> • grep “model name” /proc/cpuinfo Show CPU(s) info<br /> • lspci -tv Show PCI info<br /> • lsusb -tv Show USB info<br /> • mount | column -t List mounted filesystems on the system (and align output)<br /> # dmidecode -q | less Display SMBIOS/DMI information<br /> # smartctl -A /dev/sda | grep Power_On_Hours How long has this disk (system) been powered on in total<br /> # hdparm -i /dev/sda Show info about disk sda<br /> # hdparm -tT /dev/sda Do a read speed test on disk sda<br /> # badblocks -s /dev/sda Test for unreadable blocks on disk sda<br /> interactive (see also linux keyboard shortcuts)<br /> • readline Line editor used by bash, python, bc, gnuplot, …<br /> • screen Virtual terminals with detach capability, …<br /> • mc Powerful file manager that can browse rpm, tar, ftp, ssh, …<br /> • gnuplot Interactive/scriptable graphing<br /> • links Web browser<br /> • xdg-open open a file or url with the registered desktop application<br /> miscellaneous<br /> • alias hd=’od -Ax -tx1z -v’ Handy hexdump. (usage e.g.: • hd /proc/self/cmdline | less)<br /> • alias realpath=’readlink -f’ Canonicalize path. (usage e.g.: • realpath ~/../$USER)<br /> • set | grep $USER Search current environment<br /> touch -c -t 0304050607 file Set file timestamp (YYMMDDhhmm)<br /> • python -c “import SimpleHTTPServer as ws; ws.test()” Serve current directory tree at http://$HOSTNAME:8000/