Command Line Help

*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 $HOME directory
 (cd dir && command)Go to dir, execute command and return to current dir
*pushd .Put current dir on stack so you can popd back to it
file searching
*alias l='ls -l --color=auto'quick dir listing
*ls -lrtList files by date.
*ls /usr/bin | pr -T9 -W$COLUMNSPrint in 9 columns to width of terminal
 find -name '*.[ch]' | xargs grep -E 'expr'Search 'expr' in this dir and below.
 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 (Network efficient file copier: Use the --dry-run option for testing)
 rsync -P rsync:// 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/'~/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 dir/ && wget -nd -pHEKk local browsable version of a page to the current dir
 wget -c downloading a partially downloaded file
 wget -r -nd -np -l1 -A '*.jpg' 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' | 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 20KB/s in this case)
 wget -nv --spider --force-html -i bookmarks.htmlCheck links in a file
 wget --mirror 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 brd + dev eth0Add (or del) ip and mask (
*ip route showList routing table
 ip route add default via default gateway to
*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 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. 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>\(.*\)<\/title>.*/\1/ip;T;q'Extract title from HTML web page
 sed -i 42d ~/.ssh/known_hostsDelete a particular line
 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
set 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 -t'\0'-a1 -a2 file1 file2Union of sorted files
 join -t'\0' file1 file2Intersection of sorted files
 join -t'\0' -v2 file1 file2Difference of sorted files
 join -t'\0' -v1 -v2 file1 file2Symmetric Difference of sorted files
*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/9.58s' '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) | bcAdd a column of numbers.
*cal -3Display a calendar
*cal 9 1752Display a calendar for a particular month year
*date -d friWhat date is it this friday.
*[ $(date -d "tomorrow" +%d) = "01" ] || exitexit a script unless it's the last day of the month
*date --date='25 Dec' +%AWhat day does xmas fall on, this year
*date --date='@2147483647'Convert seconds since the epoch (1970-01-01 UTC) to date
*TZ=':America/Los_Angeles' dateWhat time is it on West coast of US (use tzselect to find TZ)
 echo "mail -s 'get the train' < /dev/null" | at 17:45Email reminder
*echo "DISPLAY=$DISPLAY xmessage cooker" | at "NOW + 30 minutes"Popup reminder
*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
 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)
*dd bs=1 seek=2TB if=/dev/null of=ext3.testCreate a large test file (taking no space).
*> filetruncate data of file or create an empty file
*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$COLUMNSList processes by mem usage.
*ps -C firefox-bin -L -o pid,tid,pcpu,stateList all threads for a particular process
*ps -p 1,2List info for particular process IDs
*last rebootShow system reboot history
*free -mShow amount of (remaining) RAM (-m displays in MB)
*watch -n.1 'cat /proc/interrupts'Watch changeable data continuously
system information('#' means root access is required)
*uname -aShow kernel version and system architecture
*head -n1 /etc/issueShow name and version of distribution
*cat /proc/partitionsShow all partitions registered on the system
*grep MemTotal /proc/meminfoShow RAM total seen by the system
*grep "model name" /proc/cpuinfoShow CPU(s) info
*lspci -tvShow PCI info
*lsusb -tvShow USB info
*mount | column -tList mounted filesystems on the system (and align output)
*grep -F capacity: /proc/acpi/battery/BAT0/infoShow state of cells in laptop battery
#dmidecode -q | lessDisplay SMBIOS/DMI information
#smartctl -A /dev/sda | grep Power_On_HoursHow long has this disk (system) been powered on in total
#hdparm -i /dev/sdaShow info about disk sda
#hdparm -tT /dev/sdaDo a read speed test on disk sda
#badblocks -s /dev/sdaTest for unreadable blocks on disk sda
*readlineLine editor used by bash, python, bc, gnuplot, ...
*screenVirtual terminals with detach capability, ...
*mcPowerful file manager that can browse rpm, tar, ftp, ssh, ...
*gnuplotInteractive/scriptable graphing
*linksWeb browser
*xdg-open .open a file or url with the registered desktop application
*alias hd='od -Ax -tx1z -v'Handy hexdump. (usage e.g.: * hd /proc/self/cmdline | less)
*alias realpath='readlink -f'Canonicalize path. (usage e.g.: * realpath ~/../$USER)
*set | grep $USERSearch current environment
 touch -c -t 0304050607 fileSet file timestamp (YYMMDDhhmm)
*python -m SimpleHTTPServerServe current directory tree at http://$HOSTNAME:8000/

This document was last modified on: 190624 19:52:54 UTC