| 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://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 $HOST |
| ssh -g -L 8080:localhost:80 root@$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 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 |
| • | 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 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 ‘1000p;1000q‘ | 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_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 |
| • | 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/9.69s’ ‘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 |
| • | [ $(date -d “tomorrow” +%d) = “01” ] || exit | exit a script unless it’s the last day of the month |
| • | date –date=’25 Dec’ +%A | What day does xmas fall on, this year |
| • | date –date=’@2147483647′ | Convert seconds since the epoch (1970-01-01 UTC) to date |
| • | TZ=’:America/Los_Angeles’ date | What time is it on West coast of US (use tzselect to find TZ) |
| echo “mail -s ‘get the train’ P@draigBrady.com < /dev/null” | at 17:45 | Email reminder |
| • | echo “DISPLAY=$DISPLAY xmessage cooker” | at “NOW + 30 minutes” | Popup reminder |
| locales |
| • | printf “%’d\n” 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 |
| 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 |
| 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 *.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 |
| • | 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 |
| • | 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 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 1,2 | List info 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 |
| 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 http://www.pixelbeat.org/ | open a file or url with the registered desktop application |
| 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 $USER | Search current environment |
| touch -c -t 0304050607 file | Set file timestamp (YYMMDDhhmm) |
| • | python -m SimpleHTTPServer | Serve current directory tree at http://$HOSTNAME:8000/ |