They suffice well enough. Despite severals flaws, they do describe the functions.
I wouldn't recommend it 100% to newbies, but it will suffice since it's the only doc I have offline.
But in case it returns a pointer to the string, then all you have to do is:
int lines = 0;
/* Assume f points to a valid FILE opened for reading... */
while( fgets(buffer, sizeof(Buffer), f) )
/* Only increment lines if fgets read an entire line, otherwise continue reading the line */
if ( Buffer[ strlen(Buffer) ] == '\n' )