sysinfo — return system information


#include <sys/sysinfo.h>
int sysinfo( struct sysinfo *info);


sysinfo() returns certain statistics on memory and swap usage, as well as the load average.

Until Linux 2.3.16, sysinfo() returned information in the following structure:

struct sysinfo {
  long   uptime;
/* Seconds since boot */
  unsigned long   loads[3];
/* 1, 5, and 15 minute load averages */
  unsigned long   totalram;
/* Total usable main memory size */
  unsigned long   freeram;
/* Available memory size */
  unsigned long   sharedram;
/* Amount of shared memory */
  unsigned long   bufferram;
/* Memory used by buffers */
  unsigned long   totalswap;
/* Total swap space size */
  unsigned long   freeswap;
/* Swap space still available */
  unsigned short   procs;
/* Number of current processes */
  char   _f[22];
/* Pads structure to 64 bytes */

In the above structure, the sizes of the memory and swap fields are given in bytes.

Since Linux 2.3.23 (i386) and Linux 2.3.48 (all architectures) the structure is:

struct sysinfo {
    long uptime;             /* Seconds since boot */
    unsigned long loads[3];  /* 1, 5, and 15 minute load averages */
    unsigned long totalram;  /* Total usable main memory size */
    unsigned long freeram;   /* Available memory size */
    unsigned long sharedram; /* Amount of shared memory */
    unsigned long bufferram; /* Memory used by buffers */
    unsigned long totalswap; /* Total swap space size */
    unsigned long freeswap;  /* Swap space still available */
    unsigned short procs;    /* Number of current processes */
    unsigned long totalhigh; /* Total high memory size */
    unsigned long freehigh;  /* Available high memory size */
    unsigned int mem_unit;   /* Memory unit size in bytes */
    char _f[20−2*sizeof(long)−sizeof(int)];
                             /* Padding to 64 bytes */

In the above structure, sizes of the memory and swap fields are given as multiples of mem_unit bytes.


On success, sysinfo() returns zero. On error, −1 is returned, and errno is set to indicate the error.



info is not a valid address.


sysinfo() first appeared in Linux 0.98.pl6.


This function is Linux-specific, and should not be used in programs intended to be portable.


All of the information provided by this system call is also available via /proc/meminfo and /proc/loadavg.




This page is part of release 5.11 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at−pages/.

  Copyright (C) 2016, Michael Kerrisk <>
Based on an earlier version of the page where a few pieces were
copyright (C) 1993 by Dan Miner ( and subsequently
others (see old changelog below).
The structure definitions are taken more or less straight from the kernel
source files.

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Modified Sat Jul 24 12:35:12 1993 by Rik Faith <>
Modified Tue Oct 22 22:29:51 1996 by Eric S. Raymond <>
Modified Mon Aug 25 16:06:11 1997 by Nicolás Lichtmaier <>