Programming

how to insert a line of text that is next to the current line(file pointer pointing to) in the file ??

ex:

suppose a file named 'Sample' has the following content in it.

Code:

this is to 
give clear idea about
the problem

if file pointer is pointing to the first line then i want to insert "12345" next to that line
so the file content becomes

Code:

this is to 
12345
give clear idea about
the problem

Note:
insertion of "12345" can any where in the file but next to the current line (the line to which file pointer is pointing to)
thanks in advance

Moderator's Comments:

Please use code tags <- click the link!

And why do you need to use a programming language for this when it can be done in a scripting language like sed awk or perl...

ya..but am reading from a file which has lines in some specific formate like

source no_of_people destination

and each line should have no_of_people=10 otherwise i have to rewrite the line below the current line with no_of_people decreased by 10.

Why can't you do this with a scripting language?