This will create a 10 MB file named testfile.txt. Change the count parameter to change the size of the file.

As one commenter pointed out, yes /dev/random can be used, but the content doesn't matter if you just need a file of a specific size for testing purposes, which is why I used /dev/zero. The file size is what matters, not the content. It's 10 MB either way. "Random" just referred to "any file - content not specific"

Makes any files in the current directory (and any sub-directories) group-readable.

Using the "! -perm /g=r" limits the number of files to only those that do not already have this property

Using "+" on the end of the -exec body tells find to build the entire command by appending all matching files before execution, so invokes chmod once only, not once per file.

Makes it easy to add keys to new ppa sources entries in apt sources.list

Now to add the key for the chromium-daily ppa:

Useful if you have to put together multiple files into one and they are scattered across subdirectories. For example: You need to combine all .sql files into one .sql file that would be sent to DBAs as a batch script.

You do get a warning if you create a file by the same extension as the ones your searching for.

find . -type f -name *.sql -exec cat {} > BatchFile.txt \;

There are two ways to use "here documents" with bash to fill stdin:

The following example shows use with the "bc" command.

a) Using a delimiter at the end of data:

> k=1024

> m=k*k

> g=k*m

> g

> eeooff

1073741824

b) using the "inline" verion with three less-than symbols:

1073741824

One nice advantage of using the triple less-than version is that the command can easily be recalled

from command line history and re-executed.

PS: in this "description", I had to use the name "less-than" to represent the less-than symbol because the commandlinefu input text box seems to eat up the real less-than symbols. Odd.

You need sysstat and gawk for this to work.

This set of commands was very convenient for me when I was preparing some xml files for typesetting a book. I wanted to check what styles I had to prepare but coudn't remember all tags that I used. This one saved me from error-prone browsing of all my files. It should be also useful if one tries to process xml files with xsl, when using own xml application.

In the above example all files have 4 lines. In "file1" consecutive lines are: "num, 1, 2, 3", in "file2": "name, Jack, Jim, Frank" and in "file3": "scores, 1300, 1100, 980". This one liner can save considerate ammount of time when you're trying to process serious portions of data. "-d" option allows one to set series of characters to be used as separators between data originating from given files.

find all email addresses in a file, printing each match. Addresses do not have to be alone on a line etc. For example you can grab them from HTML-formatted emails or CSV files, etc. Use a combination of

to filter them.

Search for the string "search" and replace it with the string "replace", on all files with the extension php in the curret folder. Do also a backup of each file with the extension "bkp".

Good for summing the numbers embedded in text - a food journal entry for example with calories listed per food where you want the total calories. Use this to monitor and keep a total on anything that ouputs numbers.

This command will open up the two files in FileMerge on OS X. You can also compare two directories.

NOTE: FileMerge is a part of the OS X Developer Tools, available on the install disc.

Tells sort to ignore all characters before the Xth position in the first field per line. If you have a list of items one per line and want to ignore the first two characters for sorting purposes, you would type "sort -k1.3". Change the "1" to change the field being sorted. The decimal value is the offset in the specified field to sort by.

If you're users have ever asked your script to email their reports in separate attachments instead of tar'ring them into one file, then you can use this. You'll need the mailx package of course. In Unix you'd want to add an additional parameter "-m"

(uuencode foo.txt foo.txt; uuencode /etc/passwd passwd.txt)|mailx -m -s "Hooosa!" someone@cmdfu.com

Uses process signal to play next selection

Pressing ESC then * will insert in the command line the results of the autocompletion.

It's hard to explain but if you look the sample output or do

you will understand quickly.

By the way, few reminders about ESC :

- Hold ESC does the same thing as tab tab

- 'ESC .' inserts the last argument of last command (can be done many times in order to get the last argument of all previous commands)

curl doesn't provide url-encoding for 'GET' data, it have an option '--data-urlencode', but its only for 'POST' data. Thats why I need to write down this commandline. With 'perl', 'php' and 'python', this is one liner, but just I wrote it for fun. Works in Ubuntu, will work in all linux varients(I hope it will work in unix varients also).

This will extract all of the urls from a firefox session (including urls in a tab's history). The sessionstore.js file is in ~/.mozilla/firefox/{firefox profile}

Share your "now playing" Amarok song in twitter!

Simple way to achieve a colored SVN diff

Obviously, you can replace 'man' command with any command in this command line to do useful things. I just want to mention that there is a way to list all the commands which you can execute directly without giving fullpath.

Normally all important commands will be placed in your PATH directories. This commandline uses that variable to get commands. Works in Ubuntu, will work in all 'manpage' configured *nix systems.

You can convert any UNIX man page to .txt