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To get total installed RAM I can use popen("sysctl -n hw.memsize", "r"), but is there some library to get this info without running external tools?

tig
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  • It's usually a bad idea to have your program make decisions based on the total memory available. A much better design would be to let the user configure how much memory it's allowed to use. Usually when programs examine available memory themselves they treat it as if all (or most) of that memory belongs to them, whereas in reality it's shared with other processes (and perhaps other users). – R.. GitHub STOP HELPING ICE Jul 09 '10 at 14:53
  • You can read about my goal: http://stackoverflow.com/questions/3211063/force-allocating-real-memory I wrote that script and by default it frees 1/8 of installed memory (512Mb is what I need when I have 4Gb total), so I need to find how much is this, also I can specify how much memory to free with parameter. I'll put it somewhere, when I have time :) – tig Jul 09 '10 at 16:22

2 Answers2

5

sysctl

You can use sysctl (more detail here)

The symbols used in this section are declared in the file sysctl.h. — Function: 

int sysctl (int *names, int nlen, void *oldval, size_t *oldlenp, void *newval, size_t newlen)

getrusage

getrusage

#include <sys/resource.h> 

int getrusage(int who, struct rusage *usage); 

struct rusage {
    struct timeval ru_utime; /* user time used */
    struct timeval ru_stime; /* system time used */
    long   ru_maxrss;        /* maximum resident set size */
    long   ru_ixrss;         /* integral shared memory size */
    long   ru_idrss;         /* integral unshared data size */
    long   ru_isrss;         /* integral unshared stack size */
    long   ru_minflt;        /* page reclaims */
    long   ru_majflt;        /* page faults */
    long   ru_nswap;         /* swaps */
    long   ru_inblock;       /* block input operations */
    long   ru_oublock;       /* block output operations */
    long   ru_msgsnd;        /* messages sent */
    long   ru_msgrcv;        /* messages received */
    long   ru_nsignals;      /* signals received */
    long   ru_nvcsw;         /* voluntary context switches */
    long   ru_nivcsw;        /* involuntary context switches */
};
Jacob
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1

You can use the api getrusage

     int who = RUSAGE_SELF;
    struct rusage usage={0,};
    int ret=0;
    ret = getrusage(who, &usage);

Look up the structure of rusage and pick the values of concern to you.

Praveen S
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