GETPIDSection: Linux Programmer's Manual (2)
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NAMEgetpid, getppid - get process identification
DESCRIPTIONgetpid() returns the process ID of the calling process. (This is often used by routines that generate unique temporary filenames.)
ERRORSThese functions are always successful.
CONFORMING TOPOSIX.1-2001, 4.3BSD, SVr4.
NOTESSince 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 ALSOclone(2), fork(2), kill(2), exec(3), mkstemp(3), tempnam(3), tmpfile(3), tmpnam(3), credentials(7)
COLOPHONThis page is part of release 3.21 of the Linux man-pages project. A description of the project, and information about reporting bugs, can be found at http://www.kernel.org/doc/man-pages/.