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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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