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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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Count the number of characters in each line

processes per user counter

use Linux ;)

Function to check whether a regular file ends with a newline

tail -c 1 "$1" returns the last byte in the file. Command substitution deletes any trailing newlines, so if the file ended in a newline $(tail -c 1 "$1") is now empty, and the -z test succeeds. However, $a will also be empty for an empty file, so we add -s "$1" to check that the file has a size greater than zero. Finally, -f "$1" checks that the file is a regular file -- not a directory or a socket, etc.

Which processes are listening on a specific port (e.g. port 80)

swap out "80" for your port of interest. Can use port number or named ports e.g. "http"

New files from parts of current buffer

On command mode in Vim you can save parts of the current buffer in another file. * The 'n' value represents the first line of the new file. * The 'm' value represents the last line of the new file. * newfile.txt is the newfile. The results are similar to this command in perl: $ perl -ne 'print if n..m' in.sql > out.sql

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" }

Programmatic way to find and set your timezone

Create a tar of directory structure only

The original suggestion did not work for me, when operating on folders located on an external mount (ie other than the root device) in Ubuntu. A variation using xargs does the trick.

Jump to a directory, execute a command and jump back to current dir

Downmix from stereo to mono and play radio stream with mplayer

The solution to a year long (and extremely frustrating) problem I've had, caused by the fact that I only have one speaker; this command downmixes the stream to monophonic output, making sure I don't miss any of the music. NOTE: When stream is in .m3u format, a -playlist option is required, as shown below: $ mplayer -af pan=1:0.5:0.5 -channels 1 -playlist radiostream.m3u This command works great with aliases for various channels in .bashrc. Sample below: $ alias radio1='mplayer -af pan=1:0.5:0.5 -channels 1 radio1stream.pls'

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