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Old 03-08-2005, 09:34 AM   #1
monil
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Registered: Mar 2005
Posts: 19

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strcat Core Dump


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
 
Old 03-08-2005, 09:51 AM   #2
hk_linux
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Registered: Nov 2004
Location: India
Distribution: RedHat, PCQLinux, Fedora
Posts: 95

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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
 
Old 03-08-2005, 09:52 AM   #3
hk_linux
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Location: India
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Also check for the return status of calloc and realloc.
 
Old 03-08-2005, 12:15 PM   #4
Hko
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Registered: Aug 2002
Location: Groningen, The Netherlands
Distribution: Debian
Posts: 2,536

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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;
}
 
Old 03-08-2005, 12:20 PM   #5
Hko
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Registered: Aug 2002
Location: Groningen, The Netherlands
Distribution: Debian
Posts: 2,536

Rep: Reputation: 111Reputation: 111
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;
}
 
  


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