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

NAME         top

       getpid, getppid - get process identification

SYNOPSIS         top

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

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

DESCRIPTION         top

       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.  This will be either the ID of the process that created this
       process using fork(), or, if that process has already terminated, the
       ID of the process to which this process has been reparented (either
       init(1) or a "subreaper" process defined via the prctl(2)
       PR_SET_CHILD_SUBREAPER operation).

ERRORS         top

       These functions are always successful.

CONFORMING TO         top

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

NOTES         top

       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         top

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

COLOPHON         top

       This page is part of release 4.11 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

Linux                            2017-05-03                        GETPID(2)

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