replace_extension (3) - Linux Manuals
replace_extension: Replaces filename+extension with a new extension tail. Allegro game programming library.
NAME
replace_extension - Replaces filename+extension with a new extension tail. Allegro game programming library.SYNOPSIS
#include <allegro.h>
char *replace_extension(char *dest, const char *filename, const char *ext, int size);
DESCRIPTION
Replaces the specified filename+extension with a new extension tail, storing at most `size' bytes into the `dest' buffer. If the filename doesn't have any extension at all, `ext' will be appended to it, adding a dot character if needed. You can use the same buffer both as input and output because Allegro internally works on a copy of the input before touching `dest'. Example:
replace_extension(buf, "C:\\game\\prog.exe",
"dat", sizeof(buf));