FILE* status = fopen( "/proc/self/status", "r" );

long   ru_idrss;         /* integral unshared data size */
long   ru_isrss;         /* integral unshared stack size */

#include <sys/resource.h>
#include <errno.h>

errno = 0;
struct rusage* memory = malloc(sizeof(struct rusage));
getrusage(RUSAGE_SELF, memory);
if(errno == EFAULT)
    printf("Error: EFAULTn");
else if(errno == EINVAL)
    printf("Error: EINVALn");
printf("Usage: %ldn", memory->ru_ixrss);
printf("Usage: %ldn", memory->ru_isrss);
printf("Usage: %ldn", memory->ru_idrss);
printf("Max: %ldn", memory->ru_maxrss);

typedef struct {
    unsigned long size,resident,share,text,lib,data,dt;
} statm_t;

void read_off_memory_status(statm_t& result)
{
  unsigned long dummy;
  char statm_path[100];
  snprintf(statm_path,99,"/proc/%d/statm",PID);

  FILE *f = fopen(statm_path,"r");
  if(!f){
    perror(statm_path);
    abort();
  }
  if(7 != fscanf(f,"%ld %ld %ld %ld %ld %ld %ld",
    &result.size,&result.resident,&result.share,&result.text,&result.lib,&result.data,&result.dt))
  {
    perror(statm_path);
    abort();
  }
  fclose(f);
}

/proc/[pid]/statm
          Provides information about memory usage, measured in pages.
          The columns are:

              size       total program size
                         (same as VmSize in /proc/[pid]/status)
              resident   resident set size
                         (same as VmRSS in /proc/[pid]/status)
              share      shared pages (from shared mappings)
              text       text (code)
              lib        library (unused in Linux 2.6)
              data       data + stack
              dt         dirty pages (unused in Linux 2.6)