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Man page of GETPID
GETPID
Section: Linux Programmer's Manual (2)
Updated: 2015-07-23
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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
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Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- ERRORS
-
- CONFORMING TO
-
- NOTES
-
- C library/kernel differences
-
- SEE ALSO
-
- COLOPHON
-
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