strcat Core Dump

monil · 03-08-2005, 08:34 AM

I have used the sys function to get the pathname as follows...

Code:

#include <string.h>

int main()
{
char *cmd = "asas/sdfsdf/ghgf";
char *dir = "dirname ";

strcat(dir,cmd);
puts(dir);
//system(dir);
return 0;
}

What i need is "dirname asas/sdfsdf/ghgf"

I need to pass this to the system function (commented...)

Thank you.

-Monil

hk_linux · 03-08-2005, 08:51 AM

The memory for cmd and dir are allocated at compile time itself. You are tyring to copy another string into the same variable without allocating more memory. Thats why it is dumping.

Try allocating for cmd, dir and then reallocate for dir and proceed.

int main()
{
char *cmd;
char *dir;
int newsize;

cmd = (char *) calloc (20,1);
dir = (char *) calloc (20,1);

strcpy (cmd, "asas/sdfsdf/ghgf");
strcpy (dir, "dirname ");
newsize = strlen(cmd) + strlen(dir) +1; // 1 for NULL

dir = (char *) realloc (dir, newsize);
strcat(dir,cmd);
puts(dir);
//system(dir);
return 0;
}

HTH

hk_linux · 03-08-2005, 08:52 AM

Also check for the return status of calloc and realloc.

Hko · 03-08-2005, 11:15 AM

Quote:

Originally posted by hk_linux
Also check for the return status of calloc and realloc.

...also free() the memory when your program doesn't need the strings anymore.
e.g.:

Code:

int main()
{
    char *cmd;
    char *dir;
    int newsize;

    cmd = (char *) calloc (20,1);
    dir = (char *) calloc (20,1);

    strcpy (cmd, "asas/sdfsdf/ghgf");
    strcpy (dir, "dirname ");
    newsize = strlen(cmd) + strlen(dir) +1; // 1 for NULL

    dir = (char *) realloc (dir, newsize);
    strcat(dir,cmd);
    puts(dir);
    //system(dir);
    free(cmd);
    free(dir);
    return 0;
}

Hko · 03-08-2005, 11:20 AM

Or, easier:

Code:

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

#define MAXLEN 80

int main()
{
    char dir[MAXLEN];

    strcpy(dir, "dirname ");
    strcat(dir, "asas/sdfsdf/ghgf");
    puts(dir);
    //system(dir);
    return 0;
}