sysinfo — returns information on overall system statistics


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


Until Linux 2.3.16, sysinfo() used to return 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 */

and the sizes were given in bytes.

Since Linux 2.3.23 (i386), 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 */

and the sizes are given as multiples of mem_unit bytes.

sysinfo() provides a simple way of getting overall system statistics. This is more portable than reading /dev/kmem.


On success, zero is returned. On error, −1 is returned, and errno is set appropriately.



pointer to struct sysinfo is invalid


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

The Linux kernel has a sysinfo() system call since 0.98.pl6. Linux libc contains a sysinfo() routine since 5.3.5, and glibc has one since 1.90.




This page is part of release 3.52 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at−pages/.

  Copyright (C) 1993 by Dan Miner (

 Permission is granted to freely distribute or modify this file
 for the purpose of improving Linux or its documentation efforts.
 If you modify this file, please put a date stamp and HOW you
 changed this file.  Thanks.   -DM

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 <>