Standard C language learning summary 10

String related operation functions

    int atoi(const char *nptr);

    function : String rotation int type

    long atol(const char *nptr);

    function : String rotation long type

    long long atoll(const char *nptr);

    function : String rotation long long type

    double atof(const char *nptr);

    function : String rotation double type

    char *strstr(const char *haystack, const char *needle);

    function : stay haystack To find out whether there is a substring needle

    Return value :needle stay haystack The first place in , Return if not found NULL

    int sprintf(char *str,const char *format, ...);

    function : Output various types of data to string str

    Return value : Number of converted characters

    int sscanf(const char *str, const char *format, ...);

    function : from str Parse and read data into variables

    Return value : The number of successfully resolved variables

    void *memcpy(void *dest, const void *src, size_t n);

    function : from src Location copy n Byte to dest The location of

    function : call chaining

    int memcmp(const void *s1, const void *s2, size_t n);

    function : Compare the values of two pieces of memory , Compare by byte , Once the results are compared, there will be no comparison later

    Return value : s1 == s2 0

            s1 < s2 negative

            s1 > s2 Positive numbers