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.
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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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/.