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creates a bash function to remove certain lines from SSH known_hosts file

sometimes you got conflicts using SSH (host changing ip, ip now belongs to a different machine) and you need to edit the file and remove the offending line from known_hosts. this does it much easier. Show Sample Output
This is sample output - yours may be different.
```
$ sshdel 30
< removes 30th line from the known_hosts file in ~/.ssh >
```
0

function sshdel { perl -i -n -e "print unless (\$. == $1)" ~/.ssh/known_hosts; }

xsawyerx · 2009-02-03 16:20:50 52
Flush and then immediately start watching a file

This is useful for keeping an eye on an error log while developing. The !^ pulls the first arg from the previous command (which needs to be run in a sub-shell for this shortcut to work).
This is sample output - yours may be different.
3

(> errors.log) && tail -f !^

root · 2009-02-03 16:08:19 94
Display which distro is installed
This is sample output - yours may be different.
77

cat /etc/issue

root · 2009-02-03 09:59:24 42
Block an IP address from connecting to a server

This appends (-A) a new rule to the INPUT chain, which specifies to drop all packets from a source (-s) IP address.
This is sample output - yours may be different.
12

iptables -A INPUT -s 222.35.138.25/32 -j DROP

root · 2009-02-02 12:42:04 76

Echo the latest commands from commandlinefu on the console

Self-referential use of wget. Show Sample Output

wget -O - http://www.commandlinefu.com/commands/browse/rss 2>/dev/null | awk '/\s*<title/ {z=match($0, /CDATA\[([^\]]*)\]/, b);print b[1]} /\s*<description/ {c=match($0, /code>(.*)<\/code>/, d);print d[1]"\n"} '

root · 2009-01-30 19:16:50 29

send tweets to twitter (and get user details)

great for outputting tweets from cron jobs and batch scripts Show Sample Output

curl --basic --user "user:pass" --data-ascii "status=tweeting%20from%20%the%20linux%20command%20line" http://twitter.com/statuses/update.json

g__j · 2009-01-30 18:08:35 86

Changes standard mysql client output to 'less'.

Changes standard mysql client output to 'less'. In another words makes query results of mysql command line client to look much better.
This is sample output - yours may be different.
5

echo -e "[mysql]\npager=less -niSFX" >> ~/.my.cnf

boombastic · 2009-01-29 11:45:52 52
scping files with streamlines compression (tar gzip)

it compresses the files and folders to stdout, secure copies it to the server's stdin and runs tar there to extract the input and output to whatever destination using -C. if you emit "-C /destination", it will extract it to the home folder of the user, much like `scp file user@server:`. the "v" in the tar command can be removed for no verbosity.
This is sample output - yours may be different.
15

tar czv file1 file2 folder1 | ssh user@server tar zxv -C /destination

xsawyerx · 2009-01-29 10:38:26 68
add all files not under version control to repository

checks which files are not under version control, fetches the names and runs them through "svn add". WARNING: doesn't work with white spaces.
This is sample output - yours may be different.
13

svn status |grep '\?' |awk '{print $2}'| xargs svn add

xsawyerx · 2009-01-29 10:33:22 81

Ping a URL sending output to file and STDOUT

The tee (as in "T" junction) command is very useful for redirecting output to two places. Show Sample Output

ping google.com | tee ping-output.txt

root · 2009-01-29 10:26:59 86

infile search and replace on N files (including backup of the files)

the addition of ".bk" to the regular "pie" idiom makes perl create a backup of every file with the extension ".bk", in case it b0rks something and you want it back
This is sample output - yours may be different.
10

perl -pi.bk -e's/foo/bar/g' file1 file2 fileN

xsawyerx · 2009-01-29 09:51:11 94
infile search and replace on N files

The "g" at the end is for global, meaning replace all occurrences and not just the first one.
This is sample output - yours may be different.
0

perl -pi -e's/foo/bar/g' file1 file2 fileN

xsawyerx · 2009-01-29 09:47:01 61
Display summary of git commit ids and messages for a given branch

Useful when quickly looking for a commit id from a branch to use with git cherry-pick. Show Sample Output
This is sample output - yours may be different.
```
0165c83d3ec75edded1066f4a042218748f5ef56     Added escaping of keywords on single view
94da1903caec853a3fd183405f3925e2e682b240     Test change to file
299fa310ddbb532a673e35f08c1944ae51f26261     Removed swap files
```
4

git log master | awk '/commit/ {id=$2} /\s+\w+/ {print id, $0}'

root · 2009-01-28 13:32:08 87
Retrieve a list of all webpages on a site

This spiders the given site without downloading the HTML content. The resulting directory structure is then parsed to output a list of the URLs to url-list.txt. Note that this can take a long time to run and you make want to throttle the spidering so as to play nicely.
This is sample output - yours may be different.
3

URL=www.example.com && wget -rq --spider --force-html "http://$URL" && find $URL -type d > url-list.txt && rm -rf $URL

root · 2009-01-27 17:59:08 73
Download all images from a site

This recursively downloads all images from a given website to your /tmp directory. The -nH and -nd switches disable downloading of the directory structure.
This is sample output - yours may be different.
36

wget -r -l1 --no-parent -nH -nd -P/tmp -A".gif,.jpg" http://example.com/images

root · 2009-01-27 17:31:22 157
Command to keep an SSH connection open

This runs the uptime command every 30 seconds to avoid an SSH connection dropping due to inactivity. Granted there are better ways of solving this problem but this is sometimes the right tool for the job.
This is sample output - yours may be different.
3

watch -n 30 uptime

root · 2009-01-27 14:49:21 118
Add all files in current directory to SVN

The --force option bypasses the warning if files are already in SVN.
This is sample output - yours may be different.
1

svn add --force *

root · 2009-01-27 10:53:27 90
Run a command on a remote machine

This counts the number of httpd processes running. Show Sample Output
This is sample output - yours may be different.
```
36
```
3

ssh user@host "ps aux | grep httpd | wc -l"

root · 2009-01-27 00:46:17 308
Find the files that contain a certain term

Simple use of find and grep to recursively search a directory for files that contain a certain term.
This is sample output - yours may be different.
3

find /path/to/dir -type f -exec grep \-H "search term" {} \;

root · 2009-01-26 16:32:14 135
Create a zip archive excluding all SVN folders
This is sample output - yours may be different.
4

zip -r myfile.zip * -x \*.svn\*

root · 2009-01-26 13:47:49 159
Synchronise a file from a remote server

You will be prompted for a password unless you have your public keys set-up.
This is sample output - yours may be different.
3

rsync -av -e ssh user@host:/path/to/file.txt .

root · 2009-01-26 13:39:24 103
Runs previous command but replacing

Really useful for when you have a typo in a previous command. Also, arguments default to empty so if you accidentally run: echo "no typozs" you can correct it with ^z
This is sample output - yours may be different.
575

^foo^bar

root · 2009-01-26 13:25:37 133
Create a quick back-up copy of a file

Uses shell expansion to create a back-up called file.txt.bak
This is sample output - yours may be different.
48

cp file.txt{,.bak}

root · 2009-01-26 12:11:29 95
Analyse a PHP file for instantations and static calls

This grabs all lines that make an instantation or static call, then filters out the cruft and displays a summary of each class called and the frequency. Show Sample Output
This is sample output - yours may be different.
```
1 parent
1 product_Item
1 promotion_Base
1 swc_Response
2 product_ViewHelper
2 product_ViewTransformer
4 promotion_Tab
5 site_Template
6 self
```
-3

grep -o "$new \(\w\+$\|\w\+::\)" file.php | sed 's/new \|:://' | sort | uniq -c | sort

root · 2009-01-26 12:08:47 59
Efficiently print a line deep in a huge log file

Sed stops parsing at the match and so is much more effecient than piping head into tail or similar. Grab a line range using sed '999995,1000005!d' < my_massive_file
This is sample output - yours may be different.
24

sed '1000000!d;q' < massive-log-file.log

root · 2009-01-26 11:50:00 1747
‹ First < 565 566 567 568 >

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Remove all .svn folders

-depth argument will cause find to do a "depth first" tree search, this will eliminate the "No such file or directory" error messages

show the difference

Blink Caps Lock on HDD activity

Some computers these days don't have an HDD activity light, but they still have a useless caps-lock, so why not re-purpose that light to show HDD activity? Requires setleds and dstat and probably needs to run as root.

FizzBuzz in one line of Bash

The (in)famous "FizzBuzz" programming challenge, answered in a single line of Bash code. The "|column" part at the end merely formats the output a bit, so if "column" is not installed on your machine you can simply omit that part. Without "|column", the solution only uses 75 characters. The version below is expanded to multiple lines, with comments added. for i in {1..100} # Use i to loop from "1" to "100", inclusive. do ((i % 3)) && # If i is not divisible by 3... x= || # ...blank out x (yes, "x= " does that). Otherwise,... x=Fizz # ...set x to the string "Fizz". ((i % 5)) || # If i is not divisible by 5, skip (there's no "&&")... x+=Buzz # ...Otherwise, append (not set) the string "Buzz" to x. echo ${x:-$i} # Print x unless it is blanked out. Otherwise, print i. done | column # Wrap output into columns (not part of the test).

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" }

Recursively chmod all dirs to 755 and all files to 644

Get a range on line with sed (first two)

Get the two first lines of a file and quit.

Crash bash, in case you ever want to for whatever reason

This is a very hackish way to do it that I'm mainly just posting for fun, and I guess technically can more accurately be said to result in undefined behavior. What the command does is tell the shell to treat libpng like it's a shell plugin (which it's most certainly not) and attempt to install a "png_create_read" command from the library. It looks for the struct with the information about the command; since it's always the command name followed by "_struct", it'll look for a symbol called "png_create_read_struct". And it finds it, since this is the name of one of libpng's functions. But bash has no way to tell it's a function instead of a struct, so it goes ahead and parses the function's code as if it was command metadata. Inevitably, bash will attempt to dereference an invalid pointer or whatever, resulting in a segfault.

convert Decimal to IP from stdin

https://stackoverflow.com/questions/10768160/ip-address-converter

bulk rename files with sed, one-liner

Far from my favorite, but works in sh and with an old sed that doesn't support '-E'

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