pointer and 2d array

[nate]

If I want to access an individual character in a pointer to an array (*argv[3]) can you access it by means of a 2d array. Say I wanted the 4th character of argv[3], is it as simple as argv[3][3] or do I need to move to contents of argv[3] to a single D array and access it that way? Thank you in advanced.

[itsme86]

That's actually an array of pointers, not a pointer to an array. And yeah you can just do argv[3][3];

[Brian]

It is as simple as argv[3][3].

e;fb

[nate]

Thanks. Yea I remember the name for it just a couple minutes ago but a name's a name. :P

[nate]

One more thing. This is a small thing I used to test how each index of argv[] was terminated and I found something interesting that I didn't know.

#include <stdio.h>

int main(int argc, char *argv[])
{
        int i;
        for ( i=0 ; i < 20; i++ )
                printf("%c",argv[1][i]);
        printf("\n");
        return 0;
}

Just prints every character of the index of argv[i]. I tested it a couple times and here were my results.

ate@ncward:~/c$ gcc try.c -o try
nate@ncward:~/c$ try cow
cowCPLUS_INCLUDE_PA
nate@ncward:~/c$ try cower
cowerCPLUS_INCLUDE_
nate@ncward:~/c$ try dddddddddddddddd
ddddddddddddddddCPL
nate@ncward:~/c$ try
Segmentation fault
nate@ncward:~/c$ try
Segmentation fault
nate@ncward:~/c$ try k
kCPLUS_INCLUDE_PATH

Im on Slack 10, 2.6.8 kernel and whatever gcc came with Slack 10. My question is simply that there is no way that this little function is portable ( maybe so I don't know ) but how are the indexs of argv[] terminated. I would just test until I hit the 'C' but I don't think this would be smart.

[itsme86]

They're terminated the same way every string is terminated in C, with a '\0'. You could rewrite your loop control like this:

for( i=0 ; argv[1][i] != '\0' ; i++ )

Also, you might want to try adding something like this right before your loop:

if(argc != 2)
{
  puts("Usage: try <word>");
  return 1;
}

This guarantees that the loop will only run if they pass a command line argument.