clear_user(9) [centos man page]

CLEAR_USER(9)						    Memory Management in Linux						     CLEAR_USER(9)

NAME

       clear_user - Zero a block of memory in user space.

SYNOPSIS

       unsigned long clear_user(void __user * to, unsigned long n);

ARGUMENTS

       to
	   Destination address, in user space.

       n
	   Number of bytes to zero.

DESCRIPTION

       Zero a block of memory in user space.

       Returns number of bytes that could not be cleared. On success, this will be zero.

COPYRIGHT

Kernel Hackers Manual 3.10					     June 2014							     CLEAR_USER(9)

SYSINFO(2)						     Linux Programmer's Manual							SYSINFO(2)

NAME

       sysinfo - returns information on overall system statistics

SYNOPSIS

       #include <sys/sysinfo.h>

       int sysinfo(struct sysinfo *info);

DESCRIPTION

       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.

RETURN VALUE

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

ERRORS

       EFAULT pointer to struct sysinfo is invalid

CONFORMING TO

       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.

SEE ALSO

       proc(5)

COLOPHON

       This page is part of release 3.44 of the Linux man-pages project.  A description of the project, and information about reporting bugs,  can
       be found at http://www.kernel.org/doc/man-pages/.

Linux								    2012-05-05								SYSINFO(2)