#include <string.h>
char *stpcpy (char *dest, char *src) - Copy one string into another.
int strcmp(char *string1, char *string2) - Compare string1 and string2 to determine alphabetic order.
char *strcpy(char *string1, char *string2) - Copy string2 to stringl.
char *strerror(int errnum) - Get error message corresponding to specified error number.
int strlen(char *string) - Determine the length of a string.
char *strncat(char *string1, char *string2, size_t n) - Append n characters from string2 to stringl.
int strncmp(char *string1, char *string2, size_t n) - Compare first n characters of two strings.
char *strncpy(char *string1, char *string2, size_t n) - Copy first n characters of string2 to stringl .
char *strnset(char *string, int c, size _t n) - Set first n characters of string to c.
char *strrchr(char *string, int c) - Find last occurrence of character c in string.