i want to read data from file. I have test.txt. In this i have data

a:123
b:223
c:323

how can search 'b' and get the data 223 and so.

I found some where that i can go via getline and than tell and for data grabing seek.
but i do not know.how to use.

You're welcome. You can always learn more functions from cplusplus website, it's a very comprehensive site :)