% strace -e open ps
open("/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
open("/lib/x86_64-linux-gnu/libprocps.so.3", O_RDONLY|O_CLOEXEC) = 3
open("/lib/x86_64-linux-gnu/libdl.so.2", O_RDONLY|O_CLOEXEC) = 3
open("/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
open("/sys/devices/system/cpu/online", O_RDONLY|O_CLOEXEC) = 3
open("/usr/lib/locale/locale-archive", O_RDONLY|O_CLOEXEC) = 3
open("/proc/self/stat", O_RDONLY)       = 3
open("/proc/uptime", O_RDONLY)          = 3
open("/proc/sys/kernel/pid_max", O_RDONLY) = 4
open("/proc/meminfo", O_RDONLY)         = 4
open("/proc/1/stat", O_RDONLY)          = 6
open("/proc/1/status", O_RDONLY)        = 6
open("/proc/2/stat", O_RDONLY)          = 6
open("/proc/2/status", O_RDONLY)        = 6
open("/proc/3/stat", O_RDONLY)          = 6
open("/proc/3/status", O_RDONLY)        = 6
…

% strace -e open ps
…
open("/proc/1/stat", O_RDONLY)          = 6
open("/proc/1/status", O_RDONLY)        = 6
open("/proc/1/cmdline", O_RDONLY)       = 6
…

int main()
   {
         :
       PROCTAB *proctab = openproc(<OPTIONS>) ;
         :
         :
       proc_t procinfo ;
       while(readproc(proctab, &procinfo) != null)
       {
          <do something with procinfo data>
       }
         :
         :
       procend(proc) ;
       return 0 ;
    }

PROCTAB *proctab = openproc(PROC_FILLMEM | PROC_FILLCOM) ;