Can I understand that there is exact word (whatever text) in the line, without the string.h library? [duplicate]

I have a text file myfile.txt, and I want to know if there is a line with "ksdjfhksjdfh"-pattern. Can I do that without <string.h> library? How?

Thank you.

I can get any line of the myfile.txt but do not know what to do next.