NAME

rev - reverse lines of a file or files

SYNOPSIS

rev [file ...]

DESCRIPTION

The rev utility copies the specified files to the standard output, reversing the order of characters in every line. If no files are specified, the standard input is read.

AVAILABILITY

The rev command is part of the util-linux-ng package and is available from ftp://ftp.kernel.org/pub/linux/utils/util-linux-ng/.

This command starts screen with 'htop', 'nethogs' and 'iotop' in split-screen. You have to have these three commands (of course) and specify the interface for nethogs - mine is wlan0, I could have acquired the interface from the default route extending the command but this way is simpler.

htop is a wonderful top replacement with many interactive commands and configuration options. nethogs is a program which tells which processes are using the most bandwidth. iotop tells which processes are using the most I/O.

The command creates a temporary "screenrc" file which it uses for doing the triple-monitoring. You can see several examples of screenrc files here: http://www.softpanorama.org/Utilities/Screen/screenrc_examples.shtml

Resizes all images in the curent directory to x resolution.

It is better than `mogrify -resize *.jpg` because of independence from extension of image (e.g. .jpg and .JPG) (:

Only tested on Linux Ubunty Hardy. Works when file names have spaces. The "-maxdepth 2" limits the find search to the current directory and the next one deeper in this example. This was faster on my system because find was searching every directory before the current directory without the -maxdepth option. Almost as fast as locate when used as above. Must use double quotes around pattern to handle spaces in file names. -print0 is used in combination with xargs -0. Those are zeros not "O"s. For xargs, -I is used to replace the following "{}" with the incoming file-list items from find. Echo just prints to the command line what is happening with mv. mv needs "{}" again so it knows what you are moving from. Then end with the move destination. Some other versions may only require one "{}" in the move command and not after the -I, however this is what worked for me on Ubuntu 8.04. Some like to use -type f in the find command to limit the type.

When you've got a list of numbers each on its row, the ECHO command puts them on a simple line, separated by space. You can then substitute the spaces with an operator. Finally, pipe it to the BC program.

Useful when you have some wrong on a server (nfs freeze/ immortal process)

Create a bunch of random files with random binary content. Basically dd dumps randomly from your hard disk to files random-file*.

Display the amount of memory used by all the httpd processes. Great in case you are being Slashdoted!

slashdot.org webserver adds an X-Bender or X-Fry HTTP header to every response!

A common mistake in Bash is to write command-line where there's command a reading a file and whose result is redirected to that file.

It can be easily avoided because of :

1) warnings "-bash: file.txt: cannot overwrite existing file"

2) options (often "-i") that let the command directly modify the file

but I like to have that small function that does the trick by waiting for the first command to end before trying to write into the file.

Lots of things could probably done in a better way, if you know one...

Same as above but slooooow it down

Next time you are leaching off of someone else's wifi use this command before you start your bittorrent ...for legitimate files only of course.

It creates a hexidecimal string using md5sum from the first few lines of /dev/urandom and splices it into the proper MAC address format. Then it changes your MAC and resets your wireless (wlan0:0).

You got some results in two variables within your shell script and would like to find the differences? Changes in process lists, reworked file contents, ... . No need to write to temporary files. You can use all the diff parameters you'll need. Maybe anything like $ grep "^>"

is helpful afterwards.

This will create the file /tmp/pkgdetails, which will contain a listing of all the files installed on your RPM-based system (RedHat, Fedora, CentOS, etc). Useful should the RPM system/database become corrupted to find which package installed which files.

In Debian based distros, this command will list 'binutils' package details which contains 'nm' command. You can replace 'nm' to any other command.

Save the script as: sort_file

Usage: sort_file < sort_me.csv > out_file.csv

This script was originally posted by Admiral Beotch in LinuxQuestions.org on the Linux-Software forum.

I modified this script to make it more portable.

Infinitely plays beeps with sinusoidally changing sound frequency. Ideal for alarm on an event.

It's the same command as submitted, but first with a command to make all characters green. It's the only way it looked "matrix-like" on my gnome-terminal.

When you use a "for" construct, it cycles on every word. If you want to cycle on a line-by-line basis (and, well, you can't use xargs -n1 :D), you can set the IFS variable to .

This will create a permanent alias to colorize the search pattern in your grep output

Handy use of bc in the command line. No need to get 'into' the bc to perform calculations

Empties all files in /var/log over 5000k. Useful if /var goes crazy or if you just haven't cleaned up in a while.