Memory usage of current process in C

You can always just open the 'files' in the /proc system as you would a regular file (using the 'self' symlink so you don't have to look up your own pid):

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

Of course, you now have to parse the file to pick out the information you need.

I came across this post: http://appcrawler.com/wordpress/2013/05/13/simple-example-of-tracking-memory-using-getrusage/

Simplified version:

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

int main() {
  struct rusage r_usage;
  getrusage(RUSAGE_SELF,&r_usage);
  // Print the maximum resident set size used (in kilobytes).
  printf("Memory usage: %ld kilobytes\n",r_usage.ru_maxrss);
  return 0;
}

(tested in Linux 3.13)

This is a terribly ugly and non-portable way of getting the memory usage, but since getrusage()'s memory tracking is essentially useless on Linux, reading /proc/<pid>/statm is the only way I know of to get the information on Linux.

If anyone know of cleaner, or preferably more cross-Unix ways of tracking memory usage, I would be very interested in learning how.

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

void read_off_memory_status(statm_t& result)
{
  unsigned long dummy;
  const char* statm_path = "/proc/self/statm";

  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);
}

From the proc(5) man-page:

   /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)

The getrusage library function returns a structure containing a whole lot of data about the current process, including these:

long   ru_ixrss;         /* integral shared memory size */
long   ru_idrss;         /* integral unshared data size */
long   ru_isrss;         /* integral unshared stack size */

However, the most up-to-date linux documentation says about these 3 fields

(unmaintained) This field is currently unused on Linux

which the manual then defines as:

Not all fields are completed; unmaintained fields are set to zero by the kernel. (The unmaintained fields are provided for compatibility with other systems, and because they may one day be supported on Linux.)

See getrusage(2)