Array only adds duplicate values

Question

When I print the contents of my array, it seems to override every element with the last command entered:

typedef struct
{
  int   argc;
  char* argv[10;
  char* myArray[80];
  size_t size;

} Command;

Inside main:

Command cmd;

cmd.myArray[cmd.size++] = buffer;

(Buffer being user input that I've checked with a printf to make sure it was the right thing being stored)

The function:

void myFunction(const Command* cmd)
{
  for (size_t i = 0; i < (cmd->size)-1; ++i)
    {
      printf("%s\n", cmd->myArray[i]);
    }
}

Any help would be greatly appreciated.

Are you allocating memory for char * pointer's before initializing it ?? And show what output you are getting. It would be easy to understand your questions — KARTHIK BHAT
– KARTHIK BHAT, Commented Jan 23, 2014 at 4:32

Barmar · Accepted Answer · 2014-01-23 04:28:33Z

4

You're setting every element of myArray to the same thing, buffer. You need to make copies of it to get distinct values:

char *temp = malloc(strlen(buffer)+1);
strcpy(temp, buffer);
cmd.myArray[cmd.size++] = temp;

answered Jan 23, 2014 at 4:28

Barmar

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Sergey Kalinichenko · Accepted Answer · 2014-01-23 04:28:02Z

2

This assignment transfers the ownership of the buffer:

cmd.myArray[cmd.size++] = buffer;

In other words, from that assignment on you must not modify the buffer, because by doing so you would alter a previously stored command. In order for this to work properly, you need to either copy the buffer, or allocate a new one on each iteration. If you would like to use a copy, add a call to strdup:

cmd.myArray[cmd.size++] = strdup(buffer);

If you would prefer to allocate a new buffer, add

cmd.myArray[cmd.size++] = buffer;
buffer = malloc(BUF_SIZE); // buffer needs to be a `char *`

answered Jan 23, 2014 at 4:28

Sergey Kalinichenko

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Comments

Ted Bigham · Accepted Answer · 2014-01-23 04:36:05Z

0

If buffer is also a char*, you might need something like this instead:

cmd.myArray[cmd.size++] = buffer[cmd.size];

answered Jan 23, 2014 at 4:36

Ted Bigham

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