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       getpid, getppid - get process identification


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

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


       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.


       These functions are always successful.


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


       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.


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


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