I use a dictionary program on SunOS and planned to port it onto my Mac. I tried to compile it but got the error message: I know the functions "re_comp" and "re_exec" are used for regular expression and I have imported unistd.h in the header file: Code: ...... #include <unistd.h> #ifdef __svr4__ #include <libgen.h> #else extern char *re_comp(char *); extern int re_exec(char *); #endif ...... I've even tried to take off the if-else condition. Anyhow the code compiles on SunOS but not on Mac. Is that because these two functions are deprecated or not provided on Mac? Any suggestion? Thanks a ton.