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number the line of a file

cat -n file : number all line cat -b file : number only non empty line see man cat
This is sample output - yours may be different.
0

cat -n file or cat -b file

eastwind · 2009-09-24 12:18:40 4
32 bits or 64 bits?
This is sample output - yours may be different.
7

sudo lshw -C cpu|grep width

sliceoflinux · 2009-09-24 11:43:00 6
Get the total length of all videos in the current dir in H:m:s

You're behind on your TV catch-up, but how far behind? This command tries to open mplayer against all files in the current dir. If it's a video file it will contain ID_LENGTH, which is summed and output in hours, minutes and seconds. Someone better at awk could probably reduce this down a lot. Show Sample Output
This is sample output - yours may be different.
```
30529.18
8h:28m:49s
```
5

mplayer -vo dummy -ao dummy -identify * 2>&1 | grep ID_LENGTH | sed 's/.*=$[0-9]*$/\1/' | xargs echo | sed 's/ /+/g' | bc | awk 'S=$1; {printf "%dh:%dm:%ds\n",S/(60*60),S%(60*60)/60,S%60}'

Strawp · 2009-09-24 10:33:19 6
Extract your list of blocked images hosts from Firefox database

I use this to replicate my blocked images hosts list between work and home to keep my browsing ad-free.
This is sample output - yours may be different.
1

sqlite3 -noheader -list ~/.mozilla/firefox/<your_profile>/permissions.sqlite "select host from moz_hosts where type='image' and permission=2"

chris_trr · 2009-09-24 06:13:10 5
Restart command if it dies.

works well in crontab.
This is sample output - yours may be different.
5

ps -C program_name || { program_name & }

grokskookum · 2009-09-24 03:35:39 3
clean up syntax and de-obfuscate perl script

the command show can be run in vim, here is the same thing on the command line cat script.pl | perl -MO=Deparse | perltidy
This is sample output - yours may be different.
3

%! perl -MO=Deparse | perltidy

grokskookum · 2009-09-24 03:32:04 8
Upgrade all perl modules via CPAN
This is sample output - yours may be different.
5

perl -MCPAN -e 'CPAN::Shell->install(CPAN::Shell->r)'

grokskookum · 2009-09-24 03:27:12 4
Recursive Ownership Change

This will change the ownership of /../../somedirectory as well as all its subdirectories so they will be be owned by user2 - typically used when a directory is owned by root:root
This is sample output - yours may be different.
-1

sudo chown -R user2:user2 /../../somedirectory

bkn390 · 2009-09-23 21:27:45 3
Quick command line math

expr will give you a quick way to do basic math from the CLI. Make sure you escape things like * and leave a space between operators and digits. Show Sample Output
This is sample output - yours may be different.
```
expr 44 + 99 + 128
271
```
4

expr 512 \* 7

chuckr · 2009-09-23 19:11:38 20

Determine configure options used for MySQL binary builds

Output is from Debian Lenny Show Sample Output

grep CONFIG $(which mysqlbug)

Velenux · 2009-09-23 17:12:37 3

Visualizing system performance data
This is sample output - yours may be different.
6

(echo "set terminal png;plot '-' u 1:2 t 'cpu' w linespoints;"; sudo vmstat 2 10 | awk 'NR > 2 {print NR, $13}') | gnuplot > plot.png

grokskookum · 2009-09-23 16:40:13 12
Show current pathname in title of terminal

This helps to keep track of what is going on when you have several tabs open in your terminal. The title automatically changes when you change directories.
This is sample output - yours may be different.
2

export PROMPT_COMMAND='echo -ne "\033]0;${PWD/#$HOME/~}\007";'

dstahlke · 2009-09-23 16:38:06 3
Execute a command with a timeout
This is sample output - yours may be different.
23

timeout 10 sleep 11

grokskookum · 2009-09-23 14:59:40 25
Remove invalid key from the known_hosts file for the IP address of a host

Quick shortcut if you know the hostname and want to save yourself one step for looking up the IP address separately.
This is sample output - yours may be different.
5

ssh-keygen -R `host hostname | cut -d " " -f 4`

flart · 2009-09-23 14:58:28 8
Save current layout of top

'top' has fancy layout modes where you can have several windows with different things displayed. You can configure a layout and then save it with 'W'. It will then be restored every time you run top. E.g. to have two colored windows, one sorted by CPU usage, the other by memory usage, run top top then press the keys <A> <z> <a> <-> <a> <z> <a> <-> <a> and then as you don?t want to repeat this the next time: <W>
This is sample output - yours may be different.
13

<Shift + W>

hfs · 2009-09-23 13:51:22 11
create SQL-statements from textfile with awk

I never can remember the syntax of awk. You can give a different -d option to cut to separate by e.g. commas. Also this allows to do more things with the generated SQL, e.g. to redirect it into different files. Show Sample Output
This is sample output - yours may be different.
```
select * from table where id = "1";
select * from table where id = "2";
select * from table where id = "3";
```
0

for each in `cut -d " " -f 1 inputfile.txt`; do echo "select * from table where id = \"$each\";"; done

hfs · 2009-09-23 13:29:16 3
print all except first collumn
This is sample output - yours may be different.
2

cut -f 2- -d " "

edo · 2009-09-23 13:12:15 3
Remove color codes (special characters) with sed
This is sample output - yours may be different.
24

sed -r "s/\x1B\[([0-9]{1,2}(;[0-9]{1,2})?)?[m|K]//g"

Cowboy · 2009-09-23 12:06:33 266
Execute a command with a timeout

In this example the command "somecommand" will be executed and sent a SIGALARM signal if it runs for more than 10 seconds. It uses the perl alarm function. It's not 100% accurate on timing, but close enough. I found this really useful when executing scripts and commands that I knew might hang E.g. ones that connect to services that might not be running. Importantly this can be used within a sequential script. The command will not release control until either the command completes or the timeout is hit. Show Sample Output
This is sample output - yours may be different.
```
$ perl -e "alarm 10; exec @ARGV" "sleep 2; echo Hello"
Hello
$ perl -e "alarm 10; exec @ARGV" "sleep 20; echo Hello"
Alarm clock
```
5

perl -e "alarm 10; exec @ARGV" "somecommand"

jgc · 2009-09-23 12:03:55 9
print all except first collumn
This is sample output - yours may be different.
5

awk '{$1=""; print}'

hoberion · 2009-09-23 08:13:40 3
Visualizing system performance data

draw `vmstat ` data using gnuplot
This is sample output - yours may be different.
0

vmstat 2 10 | awk 'NR > 2 {print NR, $13}' | gnuplot -e "set terminal png;set output 'v.png';plot '-' u 1:2 t 'cpu' w linespoints;"

Sunng · 2009-09-23 07:19:47 3
dolphins on the desktop (compiz)

xwinwrap allows you to run any program in the root desktop pane. I like to run atlantis, it goes well against Fedora 10's blue sun background. At one time this also served a useful purpose for me as a workaround for a problem that would happen when the video card went into sleep mode.
This is sample output - yours may be different.
-1

xwinwrap -ni -argb -fs -s -st -sp -nf -b -- /usr/libexec/xscreensaver/atlantis -count 20 -window-id WID &

dstahlke · 2009-09-23 05:29:21 3
snarf is a command line resource grabber.

It can transfer files through the http, gopher, finger, and ftp protocols without user interaction. It is small and fast. Show Sample Output
This is sample output - yours may be different.
```
picture.jpg                [\]       4K
5094 bytes transferred in 0.00 sec (2600.54k/sec)
```
0

snarf http://foo.bar.com/picture.jpg

JackiesJungle · 2009-09-23 04:22:57 4
run command with opposite return code

Useful in while and if statements if not grep string filename; then echo string not found; exit 1; fi
This is sample output - yours may be different.
-4

not () { "$@" && return 1 || return 0; }

arcege · 2009-09-23 01:09:53 5
Show which include directories your installation of Perl is using.

This will show where your Perl installation is looking for modules.
This is sample output - yours may be different.
0

perl -le 'print join $/, @INC'

chuckr · 2009-09-22 22:18:35 6
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Read null character seperated fields from a file

Handle any bad named file which contains ",',\n,\b,\t,` etc Store the file name as null character separated list $find . -print0 >name.lst and retrieve it using $read -r -d "" Eg: $find . -print0 >name.lst; $cat name.lst| while IFS="" read -r -d "" file; $do $ls -l "$file"; $done

check open ports without netstat or lsof

Adding formatting to an xml document for easier reading

Sometimes you're trying to read through an xml file to determine whats wrong with it and a tool had removed all the linebreaks. xmllint will go ahead and make it pretty for you.

Get your external IP address if your machine has a DNS entry

Netcat brute force on administration login panel

gpg decrypt several files

Change directory (cd) to the directory where all your encrypted files are placed, and then run the command - then you are asked to insert your secret gpg password - ubuntu 8.04

remove hostname from known_hosts

Show allocated disk space:

Convert spaces in file names to underscores

Create directory named after current date

Not a discovery but a useful one nontheless. In the above example date format is 'yyyymmdd'. For other possible formats see 'man date'. This command can be also very convenient when aliased to some meaningful name: $ alias mkdd='mkdir $(date +%Y%m%d)'

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