| Command | Description |
| • | apropos word | Show commands pertinent to word. See also threadsafe |
| | 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 (info in this case) |
| • | renice 19 -p $$ | Make shell (script) low priority. Use for non interactive tasks |
| • | look prefix | Quickly search (sorted) dictionary |
| • | grep --color expr...ion /usr/share/dict/words | Highlight occurances of regular expression in dictionary |
| | gpg -c file | Encrypt file |
| | gpg file.gpg | Decrypt file |
| | echo "mail -s 'get the train' P@draigBrady.com < /dev/null" | at 17:45 | Email reminder |
| • | watch -n1 'cat /proc/interrupts' | Watch changeable data continuously |
| • | 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 $USER | Search current environment |
| • | ls /usr/bin | pr -T9 -W$COLUMNS | Print in 9 columns to width of terminal |
| | touch -c -t 0304050607 file | Set file timestamp (YYMMDDhhmm) |
| 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 |
| CDs |
| | gzip < /dev/cdrom > cdrom.iso.gz | Save copy of data cdrom |
| | mkisofs -V NAME -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 |
| archives |
| | tar c dir/ | bzip2 > dir.tar.bz2 | Make 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/hda | gzip | ssh user@remote 'dd of=hda.gz' | Backup harddisk to remote machine |
| rsync (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 |
| file searching |
| • | alias l='ls -l --color=auto' | quick dir listing |
| • | ls -lrt | List files by date. See also newest |
| | 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 'string' | Search all regular files for 'string' in this dir and below |
| | find -maxdepth 1 -type f | xargs grep -F 'string' | Search all regular files for 'string' in this dir |
| • | find -maxdepth 1 -type d | while read dir; do (cd "$dir" && echo $PWD); 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 |
| networking (Note ifconfig, route, mii-tool, nslookup commands are obsolete) |
| • | ip link show | List interfaces |
| | ethtool interface | List interface status |
| | ip link set dev eth0 name wan | Rename eth0 to wan |
| | ip addr add 1.2.3.4/24 brd + dev eth0 | Add ip and mask(255.255.255.0) |
| | ip link set dev interface up | Bring interface up (or down) |
| | 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 ip address for name or vice versa |
| • | hostname -i | Lookup local ip address (equivalent to host `hostname`) |
| • | netstat -tupl | List internet services on a system |
| • | netstat -tup | List active connections to/from system |
| wget (multi purpose download tool) |
| • | (cd cmdline && 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/ | 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) |
| windows (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) |
| math |
| • | echo '(1 + sqrt(5))/2' | bc -l | Quick math |
| • | echo 'obase=16; ibase=10; 123' | bc | Base conversion (decimal to hexadecimal) |
| • | echo $((0x2dec)) | Base conversion (hex to dec) ((shell arithmetic expansion)) |
| • | 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 |
| text manipulation (note these use 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 |
| | sed -n '1000p;1000q' | Print 1000th line |
| | sed -n '10,20p;20q' | Print lines 10 to 20 |
| | sort file1 file1 file2 | uniq -u | Show lines in file2 not in file1 |
| • | echo 'Test' | tr '[:lower:]' '[:upper:]' | Case conversion |
| • | tr -dc '[:print:]' < /dev/urandom | Filter non printable characters |
| • | grep 'processor' /proc/cpuinfo | wc -l | Count lines |
| 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 '1970-01-01 UTC 1234567890 seconds' | Convert number of seconds since the epoch to a date |
| • | TZ=':America/Los_Angeles' date | What time is it on West coast of US (use tzselect to find TZ) |
| locales |
| • | printf "%'d\n" 1234 | Print number with thousands grouping appropriate to locale |
| • | echo "I live in `locale territory`" | Extract info from locale database |
| • | locale | cut -d= -f1 | xargs locale -kc | less | List fields in locale database |
| • | LANG=en_IE.utf8 locale int_prefix | Lookup locale info for specific country. See also ccodes |
| disk space |
| • | ls -lSr | Show files, biggest last |
| • | du -s * | sort -k1,1rn | head | Show top disk users in current dir. See also dutop |
| • | df -h | Show free disk space |
| • | df -i | Show free inodes |
| • | fdisk -l | Show disks partitions sizes and types (run as root) |
| • | rpm -q -a --queryformat '%10{SIZE}\t%{NAME}\n' | sort -k1,1n | List all packages by installed size (Bytes) on rpm distros |
| • | dpkg-query -W --showformat='${Installed-Size;10}\t${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) |
| monitoring/debugging |
| • | 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 -o rss=,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 |
| • | for wtmp in `ls -t /var/log/wtmp*`; do last reboot -f $wtmp; done | grep reboot | Show system reboot history. |
| • | free -m | Show amount of (remaining) RAM (-m displays in MB) |
| System information (see also sysinfo) |
| | hdparm -i /dev/hda | Show info about disk hda |
| | hdparm -tT /dev/hda | Do a read speed test on disk hda |
| | badblocks -s /dev/hda | Test for unreadable blocks on disk hda |
| • | mount | column -t | Show mounted filesystems on the system (and align output) |
| • | 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 |
| 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 |
| interactive |
| • | mc | Powerful filemanager that can browse rpm, tar, ftp, ssh, ... |
| • | screen | Virtual terminals with detach capability, ... |
| • | links | Web browser |
| • | gnuplot | Interactive/scriptable graphing |
| • | octave | Matlab like environment |