Thread: String Memory Allocation Program Help

So this program is supposed to take the input string and break it down to each individual argument into separate lines then add ".txt" to each end of the arguments after.
For example if I prompt
./nondebugmain programming is rewarding
The program should do this:
./nondebugmain
programming
is
rewarding
./nondebugmain.txt
programming.txt
is.txt
rewarding.txt

Here's my code so far.

Code:

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

void main(int argc, char **argv)
{

int i;
int size;
char *new=NULL;

// print out each command-line argument on a separate line.
for(i=0;i<argc;i++)
printf("Command-line argument %d: %s\n",i,argv[i]);

for(i=0;i<argc;i++)
new = (char*)malloc(strlen(argv[i]+5));

for(i=0;i<argc;i++)
{    
strcpy(new,argv[i]);
strcat(new,".txt");
argv[i]=*new;
}

// print out the arguments again
for(i=0;i<argc;i++)
printf("Command-line argument %d: %s\n",i,argv[i]);

}

There seems to be an error I missed and I cannot seem to be able to find it. Any tips would be nice and helpful. Thank you in advance

Originally Posted by leinad0213

Code:

new = (char*)malloc(strlen(argv[i]+5));

This has the unfortunate effect of doing the exact opposite of (what I assume) is the intention. You get the length of the string in argv[i] -5.

The reason is the argv[i] is a pointer, pointing at the first character of the string. If you add 5 to that address you will move ahead 5 characters in the string, and consequently 5 characters closer to the end.

What you need to do is to take the length of the string and add 5 to the argument of malloc.

Oh just noticed that bug. I fixed it but I keep getting the error "main.c:25:10: warning: assignment makes pointer from integer without a cast [enabled by default]"

You sir were an amazing help. Removing the * term from argv[i] = *new worked like a charm and the program ran just as intended. I lift my hat to you. Kudos and thank you so very much