Finds all devices with quotas:

#include <stdio.h>
#include <stdlib.h>
#include <malloc.h>
#include <mntent.h>
#include <string.h>
 
FILE *setdev()
{
 FILE *fp;
 if ((fp = setmntent(MOUNTED, "r")) == NULL) {
  fprintf(stderr, "Error calling setmntent\n");
 }
 return fp;
}
 
int getdev(FILE * fp,char *device)
{
 struct mntent *mnt;
        char *p;
        char *h;
 
 while ((mnt = getmntent(fp)) != NULL) {
  if (hasmntopt(mnt, "usrquota")) {
    if ((h = hasmntopt(mnt,"loop=/dev/loop")) != NULL) {
                    snprintf(device,255,"%s",h+5);
      p=device;
                    while(*p++) {
        if ( *p == ',') {
   *p='\0';
   break;
        }}
    return strlen(device);
   } else {
     snprintf(device,255,"%s",mnt->mnt_fsname);
    return strlen(device);
   }
  }
 
 }
 
 return 0;
}
 
int main(void)
{
 FILE *fp;
 char device[256];
 
 if ((fp = setdev()) == NULL) {
  fprintf(stderr, "setdev returned NULL\n");
  exit(1);
 }
 
 while ( getdev(fp,device)) {
  printf("%s\n", device);
 
 }
 
 endmntent(fp);
 exit(0);
}