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Replaces every ocurrences of 'old' for 'new' in all files specified

Replaces every ocurrence of 'old' for 'new' in all files specified. After the 'i' char you can put a '~' or whatever to create a backup file for each replaced with the name equal to the original plus character.
This is sample output - yours may be different.
0

perl -i -pe "s/old/new/g" *

pandres · 2009-02-05 12:07:27 66
cycle through a 256 colour palette

just for fun
This is sample output - yours may be different.
14

yes "$(seq 232 255;seq 254 -1 233)" | while read i; do printf "\x1b[48;5;${i}m\n"; sleep .01; done

pixelbeat · 2009-02-05 12:01:37 25
Serve current directory tree at http://$HOSTNAME:8000/
This is sample output - yours may be different.
846

python -m SimpleHTTPServer

pixelbeat · 2009-02-05 11:57:43 146
Shows the largest files in your archives
This is sample output - yours may be different.
0

tar -tvjf backup.tar.bz2 | sort -nrk 3 | head

Sekenre · 2009-02-05 11:57:18 89
Remove invalid host keys from ~/.ssh/known_hosts

Useful if you have to tunnel ssh through a local port and it complains of the host key being different. Much easier than manually editing the file.
This is sample output - yours may be different.
9

ssh-keygen -R \[localhost\]:8022

Sekenre · 2009-02-05 11:48:09 113
find all processes named hunger and force kill, minus the grep itself and output to a file called fu.bar
This is sample output - yours may be different.
-3

ps -auwx|egrep hunger|grep -v grep| awk '{print "kill -9",$1}' > ~/fu.bar

lendellray · 2009-02-05 11:43:38 30
rgrep: recursive grep without .svn

Only excludes .svn from filenames. Show Sample Output
This is sample output - yours may be different.
```
[nf@dev ~/css]$ rgrep sprites
./template.php:require "css_sprites.php";
./template.php: $abs_path.'/sprites/',
./template.php: 'sprites.css',
./template.php:include 'sprites.css';
```
2

alias rgrep="find . $ ! -name .svn -o -prune $ -type f -print0 | xargs -0 grep"

nf · 2009-02-05 11:23:23 34
Get the 10 biggest files/folders for the current direcotry
This is sample output - yours may be different.
51

du -s * | sort -n | tail

bambambazooka · 2009-02-05 11:18:43 33
Start urxvt and do whatever is needed to open the screen session named "main"

Open a terminal (urxvt in this case) to connect to a screen session (named "main") and create the screen session if necessary.
This is sample output - yours may be different.
0

screen -ls | grep main && urxvt -name screen -e screen -x main || urxvt -name screen -e screen -R -S main

trey · 2009-02-05 10:51:31 191
SSH to a machine's internet address if it is not present on your local network

Ping machine once, waiting 1 second for response until failing. Upon fail, ssh globally, otherwise ssh locally.
This is sample output - yours may be different.
1

ping localip -c 1 -W 1 &> /dev/null && ssh localip || ssh globalip

trey · 2009-02-05 10:40:26 524
search the manual page names and descriptions
This is sample output - yours may be different.
2

apropos somekeyword

chrisdrew · 2009-02-05 10:29:15 57
locate bin, src, and man file for a command
This is sample output - yours may be different.
4

whereis somecommand

chrisdrew · 2009-02-05 10:29:10 752
locate a command

Returns the pathnames of the files which would be executed in the current environment had its arguments been given as a command.
This is sample output - yours may be different.
0

which somecommand

chrisdrew · 2009-02-05 10:29:04 41
Search through files, ignoring .svn

Variant of find grep that ignores files with .svn in the name. Useful for searching through a local repository of source code.
This is sample output - yours may be different.
-2

find . -type f -print0 | grep -vzZ '.svn' | xargs -0 grep --color -nEHi "SEARCHTERM"

troelskn · 2009-02-05 10:27:15 39
cd canonical (resolve any symlinks)
This is sample output - yours may be different.
-1

alias cdc='cd `pwd -P`'

adavies42 · 2009-02-05 10:15:11 36
ring the bell
This is sample output - yours may be different.
3

alias beep='echo -en "\007"'

adavies42 · 2009-02-05 10:14:24 34
get a directory from one machine to another using tar and ssh
This is sample output - yours may be different.
3

ssh somemachine "cd some dir; tar zcpf - somedirname" |tar zxpf -

mischamolhoek · 2009-02-05 09:10:56 30
A nice command for summarising repeated information
This is sample output - yours may be different.
4

alias counts=sort | uniq -c | sort -nr

porges · 2009-02-05 08:24:02 519
Rip audio from a video file.

Replace and accordingly.
This is sample output - yours may be different.
68

mplayer -ao pcm -vo null -vc dummy -dumpaudio -dumpfile <output-file> <input-file>

sykora · 2009-02-05 08:17:04 40
diff two unsorted files without creating temporary files

bash/ksh subshell redirection (as file descriptors) used as input to diff
This is sample output - yours may be different.
100

diff <(sort file1) <(sort file2)

systemj · 2009-02-04 22:20:13 502
Run a command only when load average is below a certain threshold

Good for one off jobs that you want to run at a quiet time. The default threshold is a load average of 0.8 but this can be set using atrun. Show Sample Output
This is sample output - yours may be different.
```
job 6 at 2009-02-04 19:03
```
45

echo "rm -rf /unwanted-but-large/folder" | batch

root · 2009-02-04 19:07:52 45
Get the full path to a file

Useful in scripts when the file is passed in as an argument. Eg. filepath=$(realpath $1) Show Sample Output
This is sample output - yours may be different.
```
/full/path/to/examplefile.txt
```
7

realpath examplefile.txt

root · 2009-02-04 15:41:44 46
Compare a remote file with a local file

Useful for checking if there are differences between local and remote files.
This is sample output - yours may be different.
176

ssh user@host cat /path/to/remotefile | diff /path/to/localfile -

root · 2009-02-04 11:33:19 79

Search gzipped files

This decompresses the file and sends the output to STDOUT so it can be grepped. A good one to put in loops for searching directories of gzipped files, such as man pages. Show Sample Output

-7

zcat /usr/share/man/man1/grep.1.gz | grep "color"

root · 2009-02-04 09:38:45 54

Display all readline binding that use CTRL

Useful for getting to know the available keyboard shortcuts. Show Sample Output

bind -p | grep -F "\C"

root · 2009-02-03 16:22:14 57

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untar undo

List open files that have no links to them on the filesystem

I have come across a situation in the past where someone has unlinked a file by running an 'rm' command against it while it was still being written to by a running process. The problem manifested itself when a 'df' command showed a filesystem at 100%, but this did not match the total value of a 'du -sk *'. When this happens, the process continues to write to the file but you can no longer see the file on the filesystem. Stopping and starting the process will, more often than not, get rid of the unlinked file, however this is not always possible on a live server. When you are in this situation you can use the 'lsof' command above to get the PID of the process that owns the file (in the sample output this is 23521). Run the following command to see a sym-link to the file (marked as deleted): $ cd /proc/23521/fd && ls -l Truncate the sym-link to regain your disk space: $ > /proc/23521/fd/3 I should point out that this is pretty brutal and *could* potentially destabilise your system depending on what process the file belongs to that you are truncating.

Consolle based network interface monitor

ethstatus part of ethstatus package, is a consolle based monitor for network interfaces. Nicely display on screen a real time summary about bandwidth, speed and packets.

get diskusage of files modified during the last n days

get diskusage of files (in this case logfiles in /var/log) modified during the last n days: $ sudo find /var/log/ -mtime -n -type f | xargs du -ch n -> last modified n*24 hours ago Numeric arguments can be specified as +n for greater than n, -n for less than n, n for exactly n. => so 7*24 hours (about 7 days) is -7 $ sudo find /var/log/ -mtime -7 -type f | xargs du -ch | tail -n1

bash or tcsh redirect both to stdout and to a file

When plumbers use pipes, they sometimes need a T-joint. The Unix equivalent to this is 'tee'. The -a flag tells 'tee' to append to the file, rather than clobbering it. Tested on bash and tcsh.

Convert seconds to [DD:][HH:]MM:SS

Converts any number of seconds into days, hours, minutes and seconds. sec2dhms() { declare -i SS="$1" D=$(( SS / 86400 )) H=$(( SS % 86400 / 3600 )) M=$(( SS % 3600 / 60 )) S=$(( SS % 60 )) [ "$D" -gt 0 ] && echo -n "${D}:" [ "$H" -gt 0 ] && printf "%02g:" "$H" printf "%02g:%02g\n" "$M" "$S" }

Search for a line of text in a directory of files recursively (while limiting to certain file extensions)

Convert seconds to [DD:][HH:]MM:SS

Redirect incoming traffic to SSH, from a port of your choosing

Stuck behind a restrictive firewall at work, but really jonesing to putty home to your linux box for some colossal cave? Goodness knows I was...but the firewall at work blocked all outbound connections except for ports 80 and 443. (Those were wide open for outbound connections.) So now I putty over port 443 and have my linux box redirect it to port 22 (the SSH port) before it routes it internally. So, my specific command would be: $iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-ports 22 Note that I use -A to append this command to the end of the chain. You could replace that with -I to insert it at the beginning (or at a specific rulenum). My linux box is running slackware, with a kernel from circa 2001. Hopefully the mechanics of iptables haven't changed since then. The command is untested under any other distros or less outdated kernels. Of course, the command should be easy enough to adapt to whatever service on your linux box you're trying to reach by changing the numbers (and possibly changing tcp to udp, or whatever). Between putty and psftp, however, I'm good to go for hours of time-killing.

Extract IPv4 addressess from file

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