Invalid write of size 1 when using strcpy to calloc'ed location

Question

I'm trying to parse a given string into an array of NULL terminated commands, since I'm designing a C shell. So my desired command structure is :

// Null terminated commands
char** command1 = {"ls", "-l", NULL};
char** command2 = {"wc", NULL};

// Final NULL terminated array of commands
char*** cmd = {command1, command2, NULL};

And my code is :

#include<stdio.h>
#include<stdlib.h>
#include<string.h>

int main()
{
    int lastPipe = 0; // To track the last position of the "|" symbol
    int pipeCount = 0; // Count of the pipes

    char*** commands = (char***) calloc (10, sizeof(char**));
    for (int i=0; i<10; i++)
    {
        commands[i] = (char**) calloc (10, sizeof(char*));
        for (int j=0; j<10; j++)
        {
            commands[i][j] = (char*) calloc (10, sizeof(char));
        }
    }

    int a = 0;

    char* argVector[] = {"ls", "|", "wc", NULL};

    // argVector is the parsed version of the input string
    // For instance, argVector = {"ls", "|", "wc", NULL};
    for (int i=0; argVector[i] != NULL; i++)
    {
        if (strcmp(argVector[i], "|") == 0)
        {
            if (lastPipe == 0)
            {
                for (a=0; a<i; a++)
                    strcpy(commands[pipeCount][a], argVector[a]); 

                // Make NULL terminated command
                commands[pipeCount][a] = NULL;

                // Update Pipe location
                lastPipe = i;
                pipeCount++;
            }

            else
            {
                for (a = lastPipe+1; a<i; a++)
                {
                    strcpy(commands[pipeCount][a-lastPipe-1], argVector[a]);
                }

                // Make NULL terminated command
                commands[pipeCount][a-lastPipe-1] = NULL;

                // Update Pipe location
                lastPipe = i;
                pipeCount++;
           }

       }

        if (pipeCount > 0)
        {
            for(a=lastPipe + 1; a<=i; a++)
            {
                if (strcmp(argVector[a], "|") != 0)
                    // This line gives the Segmentation Fault
                    strcpy(commands[pipeCount][a-lastPipe-1], argVector[a]);
            }
            commands[pipeCount][a-lastPipe-1] = NULL;
        }

    }

    // Now, I must have a NULL terminated array of Commands
    commands[pipeCount][a] = NULL;
    commands[pipeCount] = NULL;

    // Print the commands
    for (int i=0; commands[i]!=NULL; i++)
    {
        for(int j=0; commands[i][j]!=NULL; j++)
        {
            printf("Commands[%d][%d] = %s\n", i, j, commands[i][j]);
        }
    }
}

When I run this, I get a segmentation fault, and when I looked at valgrind, it showed me :

==12458== Invalid write of size 1
==12458==    at 0x483BDC8: strcpy (vg_replace_strmem.c:512)
==12458==    by 0x109E4B: main (pipe.c:251)
==12458==  Address 0x0 is not stack'd, malloc'd or (recently) free'd

Apparently, the last strcpy has a problem, but I'm at my wits end. How can I solve this? Not sure how I'm getting these errors

EDIT : Posted full code so that you can reproduce the errors

Answer 1

Like @DavidRanieri said, the problem stems with me overwriting the elements with NULL, due to my incorrect indexing. So I simply changed those two lines with :

    commands[pipeCount+1][a] = NULL;
    commands[pipeCount+1] = NULL;

And now, everything works as expected.