The main problem is that you are copying the pointer values of result readdir
is giving you. And the pointer points to the string value, which changes
everytime read-dir is invoked.
Look below for a fix:
On Tuesday 21 September 2004 11:35 am, Bruce Shaw wrote:
> I'm working on the partitions problem in HOST-RESOURCES-MIB for Solaris.
> As it stands, the code is making all sorts of wrong decisions about which
> partition it's supposed to be using. I'm trying to write a simple
> stand-alone program to do it correctly and when that's working, fix the HRM
> code. My problem is that my application isn't behaving as I expect it to.
>
> Here's the code as it stands..
>
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <sys/types.h>
> #include <dirent.h>
> #include <unistd.h>
>
> typedef struct pentry part_entry;
>
> struct pentry {
> char *pdevname;
> char *sdname;
> char *ppath;
> };
>
> main()
> {
> FILE *fp;
// No need for *fp?
> DIR *dr;
> struct dirent *dr_entry;
> char buf[256];
> char dname[21];
>
> part_entry pentries[256];
>
> int i = 0;
> int j = 0;
>
> dr = opendir("/dev/dsk");
> while ((dr_entry = readdir(dr)) != NULL) {
> sprintf(dname,"/dev/dsk/%s",dr_entry->d_name);
> printf("fname -> %s\n",dname);
> pentries[i].pdevname = dname;
// change it to:
pentries[i].pdevname = strdup(dname);
> printf("pentry = %s\n",pentries[i].pdevname);
> if (readlink(dname, buf, 256) < 0)
> printf("bad symbolic link\b");
> else {
> printf("%s\n",buf);
> pentries[i].ppath = buf;
// and change it too:
pentries[i].ppath = strdup(buf);
> printf("pentry = %s\n",pentries[i].ppath);
> }
> unlink(dname);
// You probably just want to clean the memory:
memset(&dname, 0x00, 21);
> i++;
> }
> closedir(dr);
> printf("found %d entries\n",i);
> for (j = 0; j < i; j++) {
> printf("j= %d\n",j);
> printf(" dev= %s\n", pentries[j].pdevname);
> printf(" path= %s\n", pentries[j].ppath);
// These guys free the memory so you don't end up with memory leak.
free(pentries[i].pdevname);
free(pentries[i].ppath);
> }
> }
>
> ***********
>
> When I execute the while loop, it reads the directory and link information
> and prints it out correctly both times. When I get to the for loop at the
> end, it prints a zero, then the device name (/dev/dsk/c4t6d0s7) for the
> LAST partition read (not the first one), then segfaults.
>
> I tried changing the declarations for the strings inside pentry eg. char
> sdname[9] and the assignments to eg. strcpy(pentries[i].ppath,buf) but when
> I ran it, it blew away the contents of /dev/dsk so now I'm scared to do
> anything.
>
> Yes, I know I'm not null-terminating my strings but I'm obviously doing
> something else fundamentally wrong. Yes, I've RTFM'd the C manuals but
> they just got me more confused than ever because none of the examples are
> alike and none are adequately explained.
>
> Have I mentioned recently that I hate pointers?
>
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--
Regards,
Konrad Rzeszutek,
IBM Cambridge;l 1-617-693-1718
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