Question

I noticed that there was (at least on Mac OS X) both a <string.h> header and a <strings.h> header. man 3 string reveals that they contain different functions. Is there any reason for this?

Answer 1

strings.h comes from the BSD branch in the unix evolution. Its content has been standardized by POSIX, but most of it is marked as legacy and can be easily replaced with other functions:

int    bcmp(const void *, const void *, size_t); /* LEGACY, see memcmp */
void   bcopy(const void *, void *, size_t); /* LEGACY, see memcpy, memmove */
void   bzero(void *, size_t); /* LEGACY, see memset */
int    ffs(int);
char  *index(const char *, int); /* LEGACY, see strchr */
char  *rindex(const char *, int); /* LEGACY, see strrchr */
int    strcasecmp(const char *, const char *);
int    strncasecmp(const char *, const char *, size_t);