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Follow tail by name (fix for rolling logs with tail -f)

If you use 'tail -f foo.txt' and it becomes temporarily moved/deleted (ie: log rolls over) then tail will not pick up on the new foo.txt and simply waits with no output. 'tail -F' allows you to follow the file by it's name, rather than a descriptor. If foo.txt disappears, tail will wait until the filename appears again and then continues tailing.
This is sample output - yours may be different.
15

tail -F file

recursiverse · 2009-07-23 07:37:11 10
Display screen window number in prompt

Add this to your $HOME/.bashrc file. It will only set this prompt if it is running inside screen ($WINDOW var is set) Looks like this... ion@atomos:~[2]$ Show Sample Output
This is sample output - yours may be different.
```
ion@atomos:~[2]$
```
4

[[ "$WINDOW" ]] && PS1="\u@\h:\w[$WINDOW]\$ "

recursiverse · 2009-07-23 06:46:19 7
Analyze awk fields

Breaks down and numbers each line and it's fields. This is really useful when you are going to parse something with awk but aren't sure exactly where to start. Show Sample Output
This is sample output - yours may be different.
```
1: foo bar this is line one
 1: foo
 2: bar
 3: this
 4: is
 5: line
 6: one
2: blah blah some other stuff
 1: blah
 2: blah
 3: some
 4: other
 5: stuff
```
16

awk '{print NR": "$0; for(i=1;i<=NF;++i)print "\t"i": "$i}'

recursiverse · 2009-07-23 06:25:31 56
Attach screen over ssh

Directly attach a remote screen session (saves a useless parent bash process)
This is sample output - yours may be different.
43

ssh -t remote_host screen -r

recursiverse · 2009-07-23 06:15:04 45
Encrypted archive with openssl and tar

command to decrypt: openssl enc -aes-256-cbc -d < secret.tar.enc | tar x Of course, don't forget to rm the original files ;) You may also want to look at the openssl docs for more options.
This is sample output - yours may be different.
5

tar c folder_to_encrypt | openssl enc -aes-256-cbc -e > secret.tar.enc

recursiverse · 2009-07-23 06:03:39 4
Open windows executable, file, or folder from cygwin terminal

This executes faster than cygstart.exe I put this in a script and added it to my path: cat `which explore.sh` #!/bin/bash if [ $# -eq 0 ]; then explorer.exe $( cygpath `pwd` -w ) & else explorer.exe $( cygpath $1 -w ) & fi; Using the script you just type explore.sh file_or_executable Note: you can do this for any file that has an associated executable in the windows registry. This is quite handy if you want to open pictures or movies from xterm. Show Sample Output
This is sample output - yours may be different.
```
$ explorer $( cygpath "/path/to/executable" -w ) # Run the windows executable
$ explorer $( cygpath "movie file.avi" -w ) # Plays movie file with default player
$ explorer $( cygpath "/path/to/a folder" -w ) # Opens a folder in windows explorer
```
0

explorer $( cygpath "/path/to/file_or_exe" -w )

Highwayman · 2009-07-22 17:00:21 3660
Convert numbers to SI notation

converts any number on the 'stdin' to SI notation. My version limits to 3 digits of precious (working with 10% resistors). Show Sample Output
This is sample output - yours may be different.
```
1
10
100
1k23
10k0
100k
1M00
24k5
4k54
2P35
0m34
0n35
```
2

$ awk '{ split(sprintf("%1.3e", $1), b, "e"); p = substr("yzafpnum_kMGTPEZY", (b[2]/3)+9, 1); o = sprintf("%f", b[1] * (10 ^ (b[2]%3))); gsub(/\./, p, o); print substr( gensub(/_[[:digit:]]*/, "", "g", o), 1, 4); }' < test.dat

mungewell · 2009-07-22 16:54:14 56
find geographical location of an ip address

a shorter version Show Sample Output
This is sample output - yours may be different.
```
Leiden
```
1

lynx -dump http://www.ip-adress.com/ip_tracer/?QRY=$1|sed -nr s/'^.*My IP address city: (.+)$/\1/p'

antcore · 2009-07-22 16:14:56 75
Follow the most recently updated log files

This command finds the 5 (-n5) most frequently updated logs in /var/log, and then does a multifile tail follow of those log files. Alternately, you can do this to follow a specific list of log files: sudo tail -n0 -f /var/log/{messages,secure,cron,cups/error_log} Show Sample Output
This is sample output - yours may be different.
```
==> /var/log/cron <==

==> /var/log/messages <==

==> /var/log/lastlog <==

==> /var/log/wtmp <==

==> /var/log/secure <==

==> /var/log/lastlog <==

==> /var/log/wtmp <==
&#65533;1pts/4ts/4myusermyhost.example.com&#65533;fJ&#65533;&#65533;?
==> /var/log/secure <==
Jul 21 18:36:19 thost sshd[12730]: Accepted password for myuser from 192.168.100.7 port 50066 ssh2
Jul 21 18:36:19 thost sshd[12730]: pam_unix(sshd:session): session opened for user myuser by (uid=0)
```
5

ls -drt /var/log/* | tail -n5 | xargs sudo tail -n0 -f

kanaka · 2009-07-22 14:44:41 22
Mount a partition from within a complete disk dump

Instead of calculating the offset and providing an offset option to mount, let lomount do the job for you by just providing the partition number you would like to loop mount.
This is sample output - yours may be different.
4

lomount -diskimage /path/to/your/backup.img -partition 1 /mnt/foo

olorin · 2009-07-22 11:32:52 16
Read just the IP address of a device

Shows a single line per interface (device), with its IPv4 settings. Shorter command, better readability in output. Show Sample Output
This is sample output - yours may be different.
```
    inet 127.0.0.1/8 scope host lo
    inet 192.168.0.1/24 brd 192.168.0.255 scope global eth0
    inet 192.168.200.1/24 brd 192.168.0.255 scope global eth1
```
-3

ip addr|grep "inet "

RickDeckardt · 2009-07-22 07:38:06 7
get delicious bookmarks on your shell (text version :-))

a variation of avi4now's command - thanks by the way!
This is sample output - yours may be different.
2

curl -u 'username' https://api.del.icio.us/v1/posts/all | sed 's/^.*href=//g;s/>.*$//g;s/"//g' | awk '{print $1}' | grep 'http'

bubo · 2009-07-22 07:32:59 7
Read just the IP address of a device

to clean up the extra lines Show Sample Output
This is sample output - yours may be different.
```
127.0.0.1
192.168.1.127
```
-1

/sbin/ifconfig | grep inet | cut -f 2 -d ":" | cut -f 1 -d " " |egrep -v "^$"

giray · 2009-07-22 07:27:54 3
Matrix Style

Same as above but slooooow it down
This is sample output - yours may be different.
2

while true ; do IFS="" read i; echo "$i"; sleep .01; done < <(tr -c "[:digit:]" " " < /dev/urandom | dd cbs=$COLUMNS conv=unblock | GREP_COLOR="1;32" grep --color "[^ ]")

friedchuckles · 2009-07-22 03:59:07 9
Read just the IP address of a device

another way to output the IP address' of the system
This is sample output - yours may be different.
-1

/sbin/ifconfig | grep inet | cut -f 2 -d ":" | cut -f 1 -d " "

random_bob · 2009-07-21 21:42:04 10
search string in _all_ revisions
This is sample output - yours may be different.
1

for i in `git log --all --oneline --format=%h`; do git grep SOME_STRING $i; done

mad · 2009-07-21 19:14:51 4
Read just the IP address of a device

That one works on Linux. On BSD and Solaris, the ifconfig output is much easier to parse: /sbin/ifconfig -a | awk '/inet/{print $2}'
This is sample output - yours may be different.
0

/sbin/ifconfig | awk -F'[ :]+' '/inet addr/{print $4}'

inof · 2009-07-21 14:18:17 5
restart apache only if config works

making lots of configurations to apache and restarting the server only to find it broken just plain sucks.
This is sample output - yours may be different.
2

alias restart='apache2ctl configtest && apache2ctl restart'

digitalmechanic · 2009-07-21 14:13:15 4
Read just the IP address of a device
This is sample output - yours may be different.
-2

/sbin/ifconfig eth0 | grep "inet addr" | sed -e 's/.*inet addr:$.*$ B.*/\1/g'

digitalmechanic · 2009-07-21 14:10:39 3
Read just the IP address of a device

Found this useful for scripts where I needed to work with the machine's IP. If $DEVICE is not specified, this will return all IPs on the machine. If $DEVICE is set to a network adapter, it will return just that adapter's IP.
This is sample output - yours may be different.
-2

ifconfig $DEVICE | perl -lne '/inet addr:([\d.]+)/ and print $1'

jdob · 2009-07-21 13:48:19 6
Quick alias for case-insensitive grep

This is *NOT* about the -i option in grep. I guess everybody already knows that option. This is about the basic rule of life that the simplest things are sometimes the best. ;-) One day when I used "grep -i" for the umpteenth time, I decided to make this alias, and I've used it ever since, probably more often than plain grep. (In fact I also have aliases egrip and fgrip defined accordingly. I also have wrip="grep -wi" but I don't use this one that often.) If you vote this down because it's too trivial and simplistic, that's no problem. I understand that. But still this is really one of my most favourite aliases.
This is sample output - yours may be different.
-2

alias grip="grep -i"

inof · 2009-07-21 11:12:15 9
Print sorted count of lines

This alias finds identical lines in a file (or pipe) and prints a sorted count of them (the name "sucs" descends from the first letters of the commands). The first example shows the number of logins of users; the one who logged in most often comes last. The second example extracts web client IP addresses from a log file, then pipes the result through the "sucs" alias to find out which clients are performing the most accesses. Or pipe the first column of ps(1) output through "sucs" to see how many processes your users are running. Show Sample Output
This is sample output - yours may be different.
```
$ last | awk '{print $1}' | sucs
  23 fred
  35 kathy
 109 jim
$ awk '{print $1}' httpd-access.log | sucs
   3 10.3.45.28
  45 172.20.23.87
  97 192.128.3.4
 280 10.1.128.16
...
```
0

alias sucs="sort | uniq -c | sort -n"

inof · 2009-07-21 10:55:06 3
Simple list of apache2 virtualhosts

Simply shows virtualhosts enabled, root access not needed (assuming apache2ctl is non-root executable).
This is sample output - yours may be different.
0

/usr/sbin/apache2ctl -S

lingo · 2009-07-21 10:52:49 4
List apache2 virtualhosts

Lists virtualhosts currently enabled for apache2, showing the ServerName:port, conf file and DocumentRoot
This is sample output - yours may be different.
4

/usr/sbin/apache2ctl -S 2>&1 | perl -ne 'm@.*port\s+([0-9]+)\s+\w+\s+(\S+)\s+\((.+):.*@ && do { print "$2:$1\n\t$3\n"; $root = qx{grep DocumentRoot $3}; $root =~ s/^\s+//; print "\t$root\n" };'

lingo · 2009-07-21 10:51:30 3
Command for getting the list of files with perms, owners, groups info. Useful to find the checksum of 2 machines/images.
This is sample output - yours may be different.
-2

find / | xargs ls -l | tr -s ' ' | cut -d ' ' -f 1,3,4,9

pavanlimo · 2009-07-21 08:41:59 7
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Rename all files which contain the sub-string 'foo', replacing it with 'bar'

That is an alternative to command 8368. Command 8368 is EXTREMELY NOT clever. 1) Will break also for files with spaces AND new lines in them AND for an empty expansion of the glob '*' 2) For making such a simple task it uses two pipes, thus forking. 3) xargs(1) is dangerous (broken) when processing filenames that are not NUL-terminated. 4) ls shows you a representation of files. They are NOT file names (for simple names, they mostly happen to be equivalent). Do NOT try to parse it. Why? see this :http://mywiki.wooledge.org/ParsingLs Recursive version: $ find . -depth -name "*foo*" -exec bash -c 'for f; do base=${f##*/}; mv -- "$f" "${f%/*}/${base//foo/bar}"; done' _ {} +

Getting a domain from url, ex: very nice to get url from squid access.log

split source code to page with numbers

Create a tar of directory structure only

Quick HTML image gallery

My take on the original: even though I like the other's use of -exec echo, sed just feels more natural. This should also be slightly easier to improve. I expanded this into a script as an exercise, which took about 35 minutes (had to look up some docs): http://bitbucket.org/kniht/nonsense/src/7c1b46488dfc/commandlinefu/quick_image_gallery.py

Create date based backups

This script creates date based backups of the files. It copies the files to the same place the original ones are but with an additional extension that is the timestamp of the copy on the following format: YearMonthDay-HourMinuteSecond

Calculate sum of N numbers (Thanks to flatcap)

List only directories, one per line

omit the 1 (one) if you don't need one-per-line

generate 30 x 30 matrix

Replaces hexdump with the more succint xxd, and the sed was unnecessarily complex.

Generate hash( of some types) from string

No need to install yet another program when openssl is already installed. :-)

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