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, 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/.

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