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Copy via tar pipe while preserving file permissions (cp does not!; run this command with root!)

cp options: -p will preserve the file mode, ownership, and timestamps -r will copy files recursively also, if you want to keep symlinks in addition to the above: use the -a/--archive option
This is sample output - yours may be different.
4

cp -pr olddirectory newdirectory

stanishjohnd · 2009-08-22 22:11:24 8
Download Youtube Playlist

This will download a Youtube playlist and mostly anything http://code.google.com/apis/youtube/2.0/reference.html#Video_Feeds The files will be saved by $id.flv
This is sample output - yours may be different.
3

y=http://www.youtube.com;for i in $(curl -s $f|grep -o "url='$y/watch?v=[^']*'");do d=$(echo $i|sed "s|url\='$y/watch?v=$.*$&.*'|\1|");wget -O $d.flv "$y/get_video.php?video_id=$d&t=$(curl -s "$y/watch?v=$d"|sed -n 's/.* "t": "$[^"]*$",.*/\1/p')";done

matthewbauer · 2009-08-22 21:31:29 53
YES = NO
This is sample output - yours may be different.
4

yes n

elzapp · 2009-08-22 20:32:23 116
Copy via tar pipe while preserving file permissions (run this command as root!)

It's the same like 'cp -p' if available. It's faster over networks than scp. If you have to copy gigs of data you could also use netcat and the tar -z option in conjunction -- on the receiving end do: # nc -l 7000 | tar -xzvpf - ...and on the sending end do: # tar -czf - * | nc otherhost 7000
This is sample output - yours may be different.
1

tar -C /oldirectory -cvpf - . | tar -C /newdirector -xvf -

Cowboy · 2009-08-22 20:05:49 5
Print a random 8 digit number
This is sample output - yours may be different.
5

jot -r -n 8 0 9 | rs -g 0

curiousstranger · 2009-08-22 19:31:17 6
watch iptables counters

This will allow you to watch as matches occur in real-time. To filter out only ACCEPT, DROP, LOG..etc, then run the following command: watch 'iptables -nvL | grep -v "0 0" && grep "ACCEPT"' The -v is used to do an inverted filter. ie. NOT "0 0"
This is sample output - yours may be different.
7

watch --interval 0 'iptables -nvL | grep -v "0 0"'

Code_Bleu · 2009-08-22 18:18:05 51
Verbosely delete files matching specific name pattern, older than 15 days.
This is sample output - yours may be different.
6

find /backup/directory -name "FILENAME_*" -mtime +15 | xargs rm -vf

monkeymac · 2009-08-22 16:58:23 6
Remove empty directories

It only works in zsh
This is sample output - yours may be different.
1

rmdir **/*(/^F)

unixmonkey5248 · 2009-08-22 12:31:55 3
Cleanup firefox's database.

Sqlite database keeps collecting cruft as time passes, which can be cleaned by the 'vacuum;' command. This command cleans up the cruft in all sqlite files relating to the user you have logged in as. This command has to be run when firefox is not running, or it will exit displaying the pid of the firefox running.
This is sample output - yours may be different.
11

pgrep -u `id -u` firefox-bin || find ~/.mozilla/firefox -name '*.sqlite'|(while read -e f; do echo 'vacuum;'|sqlite3 "$f" ; done)

kamathln · 2009-08-22 10:36:05 10
List files and sizes

List files and sizes
This is sample output - yours may be different.
0

find / -type f -exec wc -c {} \; | sort -nr | head -100

hemanth · 2009-08-22 09:38:44 10
Reverse DNS lookups

Reverse DNS lookups, from a file with list of IP's, here the file is called lookups.txt
This is sample output - yours may be different.
-1

sed 's/$[0-9]*$\.$[0-9]*$\.$[0-9]*$\.$[0-9]*$.in-addr.arpa domain name pointer$.*$\./\4.\3.\2.\1\5/' \ lookups.txt

hemanth · 2009-08-22 09:37:20 4
Ping sweep without NMAP

Ping sweep without NMAP
This is sample output - yours may be different.
3

for i in `seq 1 255`; do ping -c 1 10.10.10.$i | tr \\n ' ' | awk '/1 received/ {print $2}'; done

hemanth · 2009-08-22 09:34:27 12
DNS cache snooping

DNS cache snooping
This is sample output - yours may be different.
0

for i in `cat names.txt`; do host -r $i [nameserver]; done

hemanth · 2009-08-22 09:26:31 3

Show account security settings Show Sample Output

chage -l <user>

hemanth · 2009-08-22 09:12:03 6

List all groups and the user names that were in each group

"cut" the user names from /etc/passwd and then running a loop over them. Show Sample Output
This is sample output - yours may be different.
```
avahi-autoipd:avahi-autoipd
avahi:avahi
backup:backup
bin:bin
daemon:daemon
debian-tor:debian-tor
debian-transmission:debian-transmission
games:games
gdm:gdm
gnats:gnats
haldaemon:haldaemon
```
3

for u in `cut -f1 -d: /etc/passwd`; do echo -n $u:; groups $u; done | sort

hemanth · 2009-08-22 09:06:02 7
Remove empty directories

You can also use, $ find . -depth -type d -exec rmdir {} \; 2>/dev/null
This is sample output - yours may be different.
6

find . -type d -empty -delete

hemanth · 2009-08-22 09:03:14 8
Random number generation within a range N, here N=10
This is sample output - yours may be different.
3

echo $(( $RANDOM % 10 + 1 ))

hemanth · 2009-08-22 08:57:01 5
power off system in X hours form the current time, here X=2
This is sample output - yours may be different.
1

echo init 0 | at now + 2 hours

hemanth · 2009-08-22 08:10:46 3
Day Date Time> Instead of $ or # at the terminal
This is sample output - yours may be different.
-1

export PS1='\D{%a %D %T}> '

hemanth · 2009-08-22 08:07:47 4
check open ports

Tested in Linux and OSX Show Sample Output
This is sample output - yours may be different.
```
kopete  1782   user   18u  IPv4  12568      0t0  TCP *:8010 (LISTEN)
sshd    2215   root    3u  IPv4  35583      0t0  TCP *:22 (LISTEN)
```
19

lsof -Pni4 | grep LISTEN

evenme · 2009-08-21 22:51:41 75
purge old stale messages on a qmail queue
This is sample output - yours may be different.
0

for i in `grep "unable to stat" /var/log/syslog | cut -d "/" -f 3 | sort | uniq`; do find /var/qmail/queue -name $i -type f -exec rm -v {} \; ; done

foob4r · 2009-08-21 22:03:39 3
delete all DrWeb status, failure and other messages on a postfix server
This is sample output - yours may be different.
0

mailq | grep DrWEB | awk {'print $1'} | sed s/*//g | postsuper -d -

foob4r · 2009-08-21 22:01:41 3
less an message on a postfix mailsystem with a specific message-id
This is sample output - yours may be different.
0

id=<XXXX>; find /var/spool/postfix/ -name $id -exec less {} \;

foob4r · 2009-08-21 21:58:58 3
replace old htaccess php AddHandler values with new one

Alter "AddHandler php5-cgi .php" and "AddHandler php4-cgi .php" entries to new "AddHandler x-httpd-php5 .php" respective php4 entries in all .htaccess files under /var/www Show Sample Output
This is sample output - yours may be different.
```
-
```
0

find /var/www/ -type f -name ".htaccess" -exec perl -pi -e 's/AddHandler[\s]*php(4|5)-cgi/AddHandler x-httpd-php\1/' {} \;

foob4r · 2009-08-21 21:55:22 3
floating point operations in shell scripts

allows you to use floating point operations in shell scripts Show Sample Output
This is sample output - yours may be different.
```
.6000
```
3

echo "scale=4; 3 / 5" | bc

foob4r · 2009-08-21 21:51:46 3
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A DESTRUCTIVE command to render a drive unbootable

THIS COMMAND IS DESTRUCTIVE. That said, lets assume you want to render your boot drive unbootable and reboot your machine. Maybe you want it to boot off the network and kickstart from a boot server for a fresh OS install. Replace /dev/fd0 with the device name of your boot drive and this DESTRUCTIVE command will render your drive unbootable. Your BIOS boot priority should be set to boot from HD first, then LAN.

Create a directory and change into it at the same time

How often do you make a directory (or series of directories) and then change into it to do whatever? 99% of the time that is what I do. This BASH function 'md' will make the directory path then immediately change to the new directory. By using the 'mkdir -p' switch, the intermediate directories are created as well if they do not exist.

Calculate days on which Friday the 13th occurs (inspired from the work of the user justsomeguy)

Friday is the 5th day of the week, monday is the 1st. Output may be affected by locale.

list block devices

Shows all block devices in a tree with descruptions of what they are.

Reverse a file

Patator: A Hydra brute force alternative

FAST Search and Replace for Strings in all Files in Directory

I needed a way to search all files in a web directory that contained a certain string, and replace that string with another string. In the example, I am searching for "askapache" and replacing that string with "htaccess". I wanted this to happen as a cron job, and it was important that this happened as fast as possible while at the same time not hogging the CPU since the machine is a server. So this script uses the nice command to run the sh shell with the command, which makes the whole thing run with priority 19, meaning it won't hog CPU processing. And the -P5 option to the xargs command means it will run 5 separate grep and sed processes simultaneously, so this is much much faster than running a single grep or sed. You may want to do -P0 which is unlimited if you aren't worried about too many processes or if you don't have to deal with process killers in the bg. Also, the -m1 command to grep means stop grepping this file for matches after the first match, which also saves time.

A bash timer

Starts and shows a timer. banner command is a part of the sysvbanner package. Instead of the banner an echo or figlet commands could be used. Stop the timer with Ctrl-C and elapsed time will be shown as the result.

Backup your OpenWRT config (only the config, not the whole system)

You only have to fill in your administrative account and password, and the router FQDN! I recommand to execute this command not over the internet, because there is no encryption (the username and password will be transmitted in plaintext!)

Print line immediately before a matching regex.

Use this if you don't have access to GNU grep's -B option.

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