unix commands

Command
Description

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apropos whatis
Show commands pertinent to string. See also threadsafe

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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

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time cat
Start stopwatch. Ctrl-d to stop. See also sw

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nice info
Run a low priority command (The "info" reader in this case)

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renice 19 -p $$
Make shell (script) low priority. Use for non interactive tasks

dir navigation

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cd -
Go to previous directory

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cd
Go to $HOME directory

(cd dir && command)
Go to dir, execute command and return to current dir

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pushd .
Put current dir on stack so you can popd back to it

file searching

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alias l='ls -l --color=auto'
quick dir listing

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ls -lrt
List files by date. See also newest and find_mm_yyyy

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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)

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find -type f ! -perm -444
Find files not readable by all (useful for web site)

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find -type d ! -perm -111
Find dirs not accessible by all (useful for web site)

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locate -r 'file[^/]*\.txt'
Search cached index for names. This re is like glob *file*.txt

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look reference
Quickly search (sorted) dictionary for prefix

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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)

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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)

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(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

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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

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iwlist scan
List wireless networks in range

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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)

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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)

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ip route show
List routing table

ip route add default via 1.2.3.254
Set default gateway to 1.2.3.254

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tc qdisc add dev lo root handle 1:0 netem delay 20msec
Add 20ms latency to loopback device (for testing)

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tc qdisc del dev lo root
Remove latency added above

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host pixelbeat.org
Lookup DNS ip address for name or vice versa

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hostname -i
Lookup local ip address (equivalent to host `hostname`)

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whois pixelbeat.org
Lookup whois info for hostname or ip address

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netstat -tupl
List internet services on a system

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netstat -tup
List active connections to/from system

windows networking (Note samba is the package that provides all this windows specific networking support)

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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

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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

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echo 'Test' | tr '[:lower:]' '[:upper:]'
Case conversion

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tr -dc '[:print:]' < /dev/urandom
Filter non printable characters

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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

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echo '(1 + sqrt(5))/2' | bc -l
Quick math (Calculate φ). See also bc

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echo 'pad=20; min=64; (100*10^6)/((pad+min)*8)' | bc
More complex (int) e.g. This shows max FastE packet rate

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echo 'pad=20; min=64; print (100E6)/((pad+min)*8)' | python
Python handles scientific notation

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echo 'pad=20; plot [64:1518] (100*10**6)/((pad+x)*8)' | gnuplot -persist
Plot FastE packet rate vs packet size

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echo 'obase=16; ibase=10; 64206' | bc
Base conversion (decimal to hexadecimal)

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echo $((0x2dec))
Base conversion (hex to dec) ((shell arithmetic expansion))

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units -t '100m/9.69s' 'miles/hour'
Unit conversion (metric to imperial)

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units -t '500GB' 'GiB'
Unit conversion (SI to IEC prefixes)

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units -t '1 googol'
Definition lookup

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seq 100 | (tr '\n' +; echo 0) | bc
Add a column of numbers. See also add and funcpy

calendar

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cal -3
Display a calendar

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cal 9 1752
Display a calendar for a particular month year

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date -d fri
What date is it this friday. See also day

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[ $(date -d "tomorrow" +%d) = "01" ] || exit
exit a script unless it's the last day of the month

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date --date='25 Dec' +%A
What day does xmas fall on, this year

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date --date='@2147483647'
Convert seconds since the epoch (1970-01-01 UTC) to date

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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

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echo "DISPLAY=$DISPLAY xmessage cooker" | at "NOW + 30 minutes"
Popup reminder

locales

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printf "%'d\n" 1234
Print number with thousands grouping appropriate to locale

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BLOCK_SIZE=\'1 ls -l
get ls to do thousands grouping appropriate to locale

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echo "I live in `locale territory`"
Extract info from locale database

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LANG=en_IE.utf8 locale int_prefix
Lookup locale info for specific country. See also ccodes

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locale | cut -d= -f1 | xargs locale -kc | less
List fields available in locale database

recode (Obsoletes iconv, dos2unix, unix2dos)

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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

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recode -lf windows-1252 | grep euro
Lookup table of characters

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echo -n 0x80 | recode latin-9/x1..dump
Show what a code represents in latin-9 charmap

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echo -n 0x20AC | recode ucs-2/x2..latin-9/x
Show latin-9 encoding

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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)

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ls -lSr
Show files by size, biggest last

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du -s * | sort -k1,1rn | head
Show top disk users in current dir. See also dutop

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df -h
Show free space on mounted filesystems

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df -i
Show free inodes on mounted filesystems

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fdisk -l
Show disks partitions sizes and types (run as root)

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rpm -q -a --qf '%10{SIZE}\t%{NAME}\n' | sort -k1,1n
List all packages by installed size (Bytes) on rpm distros

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dpkg-query -W -f='${Installed-Size;10}\t${Package}\n' | sort -k1,1n
List all packages by installed size (KBytes) on deb distros

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dd bs=1 seek=2TB if=/dev/null of=ext3.test
Create a large test file (taking no space). See also truncate

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> file
truncate data of file or create an empty file

monitoring/debugging

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tail -f /var/log/messages
Monitor messages in a log file

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strace -c ls >/dev/null
Summarise/profile system calls made by command

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strace -f -e open ls >/dev/null
List system calls made by command

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ltrace -f -e getenv ls >/dev/null
List library calls made by command

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lsof -p $$
List paths that process id has open

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lsof ~
List processes that have specified path open

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tcpdump not port 22
Show network traffic except ssh. See also tcpdump_not_me

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ps -e -o pid,args --forest
List processes in a hierarchy

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ps -e -o pcpu,cpu,nice,state,cputime,args --sort pcpu | sed '/^ 0.0 /d'
List processes by % cpu usage

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ps -e -orss=,args= | sort -b -k1,1n | pr -TW$COLUMNS
List processes by mem usage. See also ps_mem.py

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ps -C firefox-bin -L -o pid,tid,pcpu,state
List all threads for a particular process

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ps -p 1,2
List info for particular process IDs

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last reboot
Show system reboot history

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free -m
Show amount of (remaining) RAM (-m displays in MB)

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watch -n.1 'cat /proc/interrupts'
Watch changeable data continuously

system information (see also sysinfo) ('#' means root access is required)

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uname -a
Show kernel version and system architecture

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head -n1 /etc/issue
Show name and version of distribution

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cat /proc/partitions
Show all partitions registered on the system

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grep MemTotal /proc/meminfo
Show RAM total seen by the system

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grep "model name" /proc/cpuinfo
Show CPU(s) info

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lspci -tv
Show PCI info

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lsusb -tv
Show USB info

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mount | column -t
List mounted filesystems on the system (and align output)

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grep -F capacity: /proc/acpi/battery/BAT0/info
Show state of cells in laptop battery

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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)

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readline
Line editor used by bash, python, bc, gnuplot, ...

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screen
Virtual terminals with detach capability, ...

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mc
Powerful file manager that can browse rpm, tar, ftp, ssh, ...

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gnuplot
Interactive/scriptable graphing

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links
Web browser

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xdg-open http://www.pixelbeat.org/
open a file or url with the registered desktop application

miscellaneous

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alias hd='od -Ax -tx1z -v'
Handy hexdump. (usage e.g.: • hd /proc/self/cmdline | less)

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alias realpath='readlink -f'
Canonicalize path. (usage e.g.: • realpath ~/../$USER)

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set | grep $USER
Search current environment

touch -c -t 0304050607 file
Set file timestamp (YYMMDDhhmm)

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python -m SimpleHTTPServer
Serve current directory tree at http://$HOSTNAME:8000/