Free Knowledge Resources


Linux Manual Pages


Free Software * Books

Source Code

Free Media

Linux

mincore(2)


NAME

   mincore - determine whether pages are resident in memory

SYNOPSIS

   #include <unistd.h>
   #include <sys/mman.h>

   int mincore(void *addr, size_t length, unsigned char *vec);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

   mincore():
       Since glibc 2.19:
           _DEFAULT_SOURCE
       Glibc 2.19 and earlier:
           _BSD_SOURCE || _SVID_SOURCE

DESCRIPTION

   mincore()  returns a vector that indicates whether pages of the calling
   process's virtual memory are resident in core (RAM), and  so  will  not
   cause  a  disk  access  (page fault) if referenced.  The kernel returns
   residency information about the pages starting at the address addr, and
   continuing for length bytes.

   The  addr  argument  must  be  a multiple of the system page size.  The
   length argument need not be a multiple of  the  page  size,  but  since
   residency   information   is   returned  for  whole  pages,  length  is
   effectively rounded up to the next multiple of the page size.  One  may
   obtain the page size (PAGE_SIZE) using sysconf(_SC_PAGESIZE).

   The   vec   argument  must  point  to  an  array  containing  at  least
   (length+PAGE_SIZE-1)  /  PAGE_SIZE  bytes.   On   return,   the   least
   significant  bit  of each byte will be set if the corresponding page is
   currently resident in memory, and be clear otherwise.  (The settings of
   the  other bits in each byte are undefined; these bits are reserved for
   possible later use.)  Of course the information returned in vec is only
   a  snapshot: pages that are not locked in memory can come and go at any
   moment, and the contents of vec may already be stale by the  time  this
   call returns.

RETURN VALUE

   On  success,  mincore()  returns  zero.   On error, -1 is returned, and
   errno is set appropriately.

ERRORS

   EAGAIN kernel is temporarily out of resources.

   EFAULT vec points to an invalid address.

   EINVAL addr is not a multiple of the page size.

   ENOMEM length is greater than (TASK_SIZE - addr).  (This could occur if
          a  negative value is specified for length, since that value will
          be interpreted as a large unsigned integer.)   In  Linux  2.6.11
          and earlier, the error EINVAL was returned for this condition.

   ENOMEM addr to addr + length contained unmapped memory.

VERSIONS

   Available since Linux 2.3.99pre1 and glibc 2.2.

CONFORMING TO

   mincore()  is  not specified in POSIX.1, and it is not available on all
   UNIX implementations.

BUGS

   Before kernel 2.6.21, mincore() did not return correct information  for
   MAP_PRIVATE  mappings,  or  for  nonlinear  mappings (established using
   remap_file_pages(2)).

SEE ALSO

   mlock(2), mmap(2)

COLOPHON

   This page is part of release 4.09 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
   https://www.kernel.org/doc/man-pages/.



Opportunity


Personal Opportunity - Free software gives you access to billions of dollars of software at no cost. Use this software for your business, personal use or to develop a profitable skill. Access to source code provides access to a level of capabilities/information that companies protect though copyrights. Open source is a core component of the Internet and it is available to you. Leverage the billions of dollars in resources and capabilities to build a career, establish a business or change the world. The potential is endless for those who understand the opportunity.

Business Opportunity - Goldman Sachs, IBM and countless large corporations are leveraging open source to reduce costs, develop products and increase their bottom lines. Learn what these companies know about open source and how open source can give you the advantage.



Free Software


Free Software provides computer programs and capabilities at no cost but more importantly, it provides the freedom to run, edit, contribute to, and share the software. The importance of free software is a matter of access, not price. Software at no cost is a benefit but ownership rights to the software and source code is far more significant.

Free Office Software - The Libre Office suite provides top desktop productivity tools for free. This includes, a word processor, spreadsheet, presentation engine, drawing and flowcharting, database and math applications. Libre Office is available for Linux or Windows.



Free Books


The Free Books Library is a collection of thousands of the most popular public domain books in an online readable format. The collection includes great classical literature and more recent works where the U.S. copyright has expired. These books are yours to read and use without restrictions.

Source Code - Want to change a program or know how it works? Open Source provides the source code for its programs so that anyone can use, modify or learn how to write those programs themselves. Visit the GNU source code repositories to download the source.



Education


Study at Harvard, Stanford or MIT - Open edX provides free online courses from Harvard, MIT, Columbia, UC Berkeley and other top Universities. Hundreds of courses for almost all major subjects and course levels. Open edx also offers some paid courses and selected certifications.

Linux Manual Pages - A man or manual page is a form of software documentation found on Linux/Unix operating systems. Topics covered include computer programs (including library and system calls), formal standards and conventions, and even abstract concepts.


birds banner