CODEWITHSUNDEEP
cpointersfile-iostrtok
Zahaib Akhtar
Zahaib Akhtar

Reputation: 1078

Using a character pointer array to store multiple char arrays

I have the following code in which I'm reading lines from a file and want to save them using a character pointer array. As I'm using one buffer inside my file read loop all my pointers in the character array end up pointing towards the last line read from file as the last line is the one that is currently held in the buffer when the loop terminates. How can I store them such that each pointer in the character array points to different char arrays in the order they were read.

int num_clients_to_start = 0;
char *token1, *token2,  *str;
FILE* fp;
char bufr[256];
char testchar[255] = {}; 
char *start_client[10];

while(fgets(bufr, 256, fp) != NULL){

    if(bufr[0] == '#'|| bufr[0] == '\n')
    continue;

    str = bufr;

    token2 = "";  /* initializing an empty token 2 */
        for(str = bufr;  ;str = NULL){
    token1 = strtok(str, " ");
    if(strcmp(token2, "client_name") == 0){
        sprintf(testchar,"%s", token1);
            start_client[num_clients_to_start] = testchar;
        num_clients_to_start++;
    }                   

    token2 = token1;

    if(str == NULL){
            break;
    }
  }//end of for loop

}//end of while loop

printf("client1 = %s client2 = %s client3 = %s",start_client[0],start_client[1],start_client[2]);

My input file is the following:

client_name abc
client_name def
client_name xyz

And print statement outputs:

client1 = xyz
client2 = xyz
client3 = xyz

Upvotes: 1

Views: 3958

Answers (2)

David Ranieri
David Ranieri

Reputation: 41036

Note that start_client[0], [1], [2] are all pointers to the last string (readed by fgets)

Use strdup in order to allocate them:

start_client[num_clients_to_start] = strdup(testchar);

As strdup can be an external identifier, use a prototype

#include <string.h>

char *strdup(const char *s);

And don't forget to free() at the end

Upvotes: 3

Some programmer dude
Some programmer dude

Reputation: 409364

You assign the same pointer to all entries in the start_client array. The array testchar will get different contents, but the pointer to it will always be the same. You might want to make start_client an array of arrays of char, and copy the string instead.

Like

char start_client[10][256];

And

strcpy(start_client[num_clients_to_start++], token1);

Upvotes: 1

Related Questions