touch a big file using c or c++ or php??

hey.. guys..

sorry i can't type in korean

i want to ask you guys about touching a big file using c or c++ or any web script languages.

how big is it?? may be. 100M or 500M...

There is one situation to search information from a big file.

don't allow to use Fork, thread

i don't expect the soultion which is simply.. change buffer size and so on..

what method is suitable for this case?

thanks.