Question

How can I find out the size of a file I opened with an application written in C?

I would like to know the size because I want to put the content of the loaded file into a string, which I allocate using malloc().

Just writing malloc(10000*sizeof(char)); is IMHO a bad idea.

Answer 1

You need to seek to the end of the file and then ask for the position:

fseek(fp, 0L, SEEK_END); sz = ftell(fp); 

You can then seek back, e.g.:

fseek(fp, 0L, SEEK_SET); 

or (if seeking to go to the beginning)

rewind(fp);