Shell Programming and Scripting

HI there !

can you please explain me about "unix2does" command like >> when we used ? what it does ? ...

unix2dos, the program that converts text files in UNIX format to DOS format.

oh thanks dude .. do u have any idea when will we use this in the UNIX script??

unix2dos is a Unix tool to convert an ASCII text file from Unix format (line break) to DOS format (carriage return and line break) and vice versa. When invoked as unix2dos the program will convert a Unix text file to DOS format, when invoked as dos2unix it will convert a DOS text file to UNIX format.
When to use it , simply it depends on your needs one good example if you have bunch of files and you want to automate the process of conversion between UNIX ASCII text format to Windows ASCII text format and vice versa , Just invoke unix2dos from a script.
Here some alternatives to unix2dos in PERL and sed

Code:

$ perl -i -p -e 's/\n/\r\n/' file
$ sed -i -e 's/$/\r/' file

and the reverse operation in some native UNIX tools such tr

Code:

$ tr -d '\r' < file > file2
$ perl -i -p -e 's/\r//' file
$ sed -i -e 's/\r//' file