字符串操作

(strcpy)和内存拷贝(memcpy)有什么不同?它们适合于在哪种情况下使用?

    strcpy()函数只能拷贝字符串。strcpy()函数将源字符串的每个字节拷贝到目录字符串中，当遇到字符串末尾的null字符(\0)时，它会删去该字符，并结束拷贝。
    memcpy()函数可以拷贝任意类型的数据。因为并不是所有的数据都以null字符结束，所以你要为memcpy()函数指定要拷贝的字节数。
      在拷贝字符串时，通常都使用strcpy()函数；在拷贝其它数据(例如结构)时，通常都使用memcpy()函数。

例如：

#include
#include
typedef struct cust_str {
    int id ;
    char last_name [20] ;
    char first_name[15];
} CUSTREC;

int main (void)
{
    char * src_string = "This is the source string" ;
    char dest_string[50];
    CUSTREC src_cust;
    CUSTREC dest_cust;
    printf("Hello! I'm going to copy src_string into dest_string!\n");
    /* Copy src_ string into dest-string. Notice that the destination
      string is the first argument. Notice also that the strcpy()
      function returns a pointer to the destination string. */
    printf("Done! dest_string is: %s\n" ,
        strcpy(dest_string, src_string)) ;
    printf("Encore! Let's copy one CUSTREC to another. \n") ;
    prinft("I'll copy src_cust into dest_cust. \n");
    /* First, intialize the src_cust data members. */
    src_cust. id = 1 ;
    strcpy(src_cust. last_name, "Strahan");
    strcpy(src_cust. first_name, "Troy");
    /* Now, Use the memcpy() function to copy the src-cust structure to
        the dest_cust structure. Notice that, just as with strcpy(), the
        destination comes first. */
    memcpy(&dest_cust, &src_cust, sizeof(CUSTREC));
    printf("Done! I just copied customer number # %d (%s %s). " ,
        dest_cust. id, dest_cust. first_name, dest_cust. last_name) ;

   system("pause");

   return (0);
}

//删去字符串尾部空格的函数

/* The rtrim() function removes trailing spaces from a string. */

char * rtrim(char*str)

{

    int n = strlen(str) -1;/* Start at the character BEFORE
                               the null character (\0). */

    while(n>0)

    {

        if(*(str+n) != '')/* If we find a nonspace character: */

        {

              *(str+n+1) = '\0';/* Put the null character at one
                                     character past our current
                                     position. */

              break;

        }

        else

         {

              n--;

          }

    }

    return str;*Return a pointer to the string*/

}

测试：

int main(void)
{
    char trail_str[] = "This string has trailing spaces in it   ";
   /* Show the status of the string before calling the rtrim()
       function. */
    printf("Before calling rtrim(), trail_str is '%s'\n" , trail_str);
    printf("and has a length of %d. \n" , strlen (trail_str));
   /* Call the rtrimO function to remove the trailing blanks. */
    rtrim(trail_str) ;
   /* Show the status of the string
       after calling the rtrim() function. */
    printf("After calling rttim(), trail_ str is '%s'\n", trail_str );
    printf ("and has a length of %d. \n" , strlen(trail_str)) ;
   
    system("pause");
    return(0);
}