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CentOS 7.0 - man page for getppid (centos section 2)

GETPID(2)				      Linux Programmer's Manual 				    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, 4.3BSD, SVr4.
NOTES
Since glibc version 2.3.4, the glibc wrapper function for getpid() caches PIDs, so as to avoid additional sys- tem calls when a process calls getpid() repeatedly. Normally this caching is invisible, but its correct oper- ation 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)
COLOPHON
This page is part of release 3.53 of the Linux man-pages project. A description of the project, and informa- tion about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/. Linux 2008-09-23 GETPID(2)
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