There are two types of functions in string.h. The str... functions such as strcat() and the mem... functions like memset(). Generally the Mem... functions are for a fixed size and have an extra parameter specifying it while the str... require the terminating '\0'. The mem... functions are not for string handling but for working with structs etc. I list them here for completeness.
- void * memset(void *s,int c, size_t n) - sets n bytes of *s to the value c and returns s.
- void memcpy(void *to, const void* from,size_t n) - copies a block of n bytes from *from to *to. Must not overlap.
- void memmove(void *to, const void* from, size_t n) - copies a block of n bytes from *from to *to. Can overlap.
- int memcmp(const void *s1, const void* s2, size_t n) - compares n bytes from *s1 with *s2. 0 if identical.
- void * memchr(const void *s, int c, size_t n) - Searches n bytes of *s for the value c and returns a void * pointer to it if found, null if not found.
This shows two badge structures initialized using memset() to clear all fields. The strcpy() function is used to assign strings and then memcpy() used to copy one badge into another before printing the values out. The memcpy() and memmove() functions are identical except that memmove() allows overlapping and memcpy() doesn't. Most CPUs have instructions to do fast copying and the compiler will use this if it can.
On the next page : A look at the char functions in ctype.h
