如何复制char ** a-C的值

Question

In this code:

#include <stdio.h>
void givetome(char** skey);
int main(int argc, const char * argv[]) {
    char *skey[5];
    givetome(&skey[5]);
    printf("%s\n",*skey);
    return 0;
}
void givetome(char **skey){
    char f[5]={'g','h','f','d','s'};
    for (int i=0; i<5; i++) {
        *skey[i]=f[i];
    }
}

I'm not able to copy the values from the vector "f" to the vector "skey". Someone to help?

Answer 1

With givetome(&skey[5]) , you start assigning characters at the end of skey and thereby exceed array bounds then. With givetome(&skey[0]) or simply givetome(skey) it should work.

BTW: as you print the result as a string, you'll need to terminate the string with '\\0' :

#include <stdio.h>
void givetome(char* skey);
int main(int argc, const char * argv[]) {
    char skey[6];
    givetome(skey);
    skey[5] = '\0';
    printf("%s\n",skey);
    return 0;
}
void givetome(char *skey){
    char f[5]={'g','h','f','d','s'};
    for (int i=0; i<5; i++) {
        skey[i]=f[i];
    }
}

Answer 2

Lots of problems here.

You defined skey as an array of pointers. What you want is an array of characters:

char skey[5];

Then when you call the function:

givetome(&skey[5]);

You pass the address of the array element with index 5. The largest index in an array of size 5 is 4, so you're passing a pointer to one past the end of the array. You want to pass the array by name, which passes in the address of the first element.

givetome(skey);

Then, since we've redefined skey , we need to change givetome to accept a char * . Then when assigning, assign to skey[i] , not *skey[i] .

You'll also have a problem printing because %s expects a string, which is defined as a null-terminated array of characters. The array doesn't contain a null byte, so printing will read past the end of the array. So add a null byte to the end of f and save room for it in skey .

With all the changes, the code should look like this.

#include <stdio.h>

void givetome(char *skey);

int main(int argc, const char * argv[]) {
    char skey[6];
    givetome(skey);
    printf("%s\n", skey);
    return 0;
}

void givetome(char *skey){
    char f[6]={'g','h','f','d','s', '\0'};
    for (int i=0; i<6; i++) {
        skey[i]=f[i];
    }
}