Free Knowledge Resources


Linux Manual Pages


Free Software * Books

Source Code

Free Media

Linux

getpid(2)


NAME

   getpid, getppid - get process identification

SYNOPSIS

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

   pid_t getpid(void);
   pid_t getppid(void);

DESCRIPTION

   getpid() returns the process ID of the calling process.  (This is often
   used by routines that generate unique temporary filenames.)

   getppid() returns the process ID of the parent of the calling process.

ERRORS

   These functions are always successful.

CONFORMING TO

   POSIX.1-2001, POSIX.1-2008, 4.3BSD, SVr4.

NOTES

   If  the  caller's  parent  is  in  a  different  PID   namespace   (see
   pid_namespaces(7)), getppid() returns 0.

   C library/kernel differences
   Since  glibc  version  2.3.4,  the  glibc wrapper function for getpid()
   caches PIDs, so as to avoid additional  system  calls  when  a  process
   calls getpid() repeatedly.  Normally this caching is invisible, but its
   correct operation relies  on  support  in  the  wrapper  functions  for
   fork(2),  vfork(2),  and clone(2): if an application bypasses the glibc
   wrappers for these system calls by using syscall(2),  then  a  call  to
   getpid()  in  the  child will return the wrong value (to be precise: it
   will return the PID of the parent  process).   See  also  clone(2)  for
   discussion  of  a  case  where getpid() may return the wrong value even
   when invoking clone(2) via the glibc wrapper function.

SEE ALSO

   clone(2),   fork(2),   kill(2),   exec(3),   mkstemp(3),    tempnam(3),
   tmpfile(3), tmpnam(3), credentials(7), pid_namespaces(7)

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