HPUX fork[2]

 fork(2)                                                             fork(2)





 NAME
      fork - create a new process

 SYNOPSIS
      #include <unistd.h>

      pid_t fork(void);

 DESCRIPTION
      fork() causes the creation of a new process.  The new process (child
      process) is an exact copy of the calling process (parent process).
      This means that the child process inherits the following attributes
      from the parent process:

           o  Real, effective, and saved user ID.  o
           o  Real, effective, and saved group ID.
           o  List of supplementary group IDs (see getgroups(2)).
           o  Process group.  ID
           o  Environment.
           o  File descriptors.
           o  Close-on-exec flags (see exec(2)).
           o  Signal handling settings (SIG_DFL, SIG_IGN, address).
           o  Signal mask (see sigvector(2)).
           o  Profiling on/off status (see profil(2)).
           o  Command name in the accounting record (see acct(4)).
           o  Nice value (see nice(2)).
           o  All attached shared memory segments (see shmop(2)).
           o  Current working directory
           o  Root directory (see chroot(2)).
           o  File mode creation mask (see umask(2)).
           o  File size limit (see ulimit(2)).
           o  Real-time priority (see rtprio(2)).

      Each of the child's file descriptors shares a common open file
      description with the corresponding file descriptor of the parent.
      This implies that changes to the file offset, file access mode, and
      file status flags of file descriptors in the parent also affect those
      in the child, and vice-versa.

      The child process differs from the parent process in the following
      ways:

           The child process has a unique process ID.  The child process ID
           also does not match any active process group ID.

           The child process has a different parent process ID (which is the
           process ID of the parent process).

           The set of signals pending for the child process is initialized
           to the empty set.




 Hewlett-Packard Company            - 1 -     HP-UX Release 9.0: August 1992






 fork(2)                                                             fork(2)





           The trace flag (see ptrace(2) PT_SETTRC request) is cleared in
           the child process.

           The AFORK flag in the ac_flags component of the accounting record
           is set in the child process.

           Process locks, text locks, and data locks are not inherited by
           the child (see plock(2)).

           All semadj values are cleared (see semop(2)).

           The child process's values of tms_utime, tms_stime, tms_cutime,
           and tms_cstime are set to zero (see times(2)).

           The time left until an alarm clock signal is reset to 0 (clearing
           any pending alarm), and all interval timers are set to 0
           (disabled).

      The vfork(2) system call can be used to fork processes more quickly
      than fork(), but has some restrictions.  See vfork(2) for details.

      If a parent and child process both have a file opened and the parent
      or child closes the file, the file is still open for the other
      process.

 RETURN VALUE
      Upon successful completion, fork() returns a value of 0 to the child
      process and returns the process ID of the child process to the parent
      process.  Otherwise, a value of -1 is returned to the parent process,
      no child process is created, and errno is set to indicate the error.

      The parent and child processes resume execution immediately after the
      fork() call; they are distinguished by the value returned by fork.

 ERRORS
      fork() fails and no child process is created if one or more of the
      following is true:

           [EAGAIN]       The system-imposed limit on the total number of
                          processes under execution would be exceeded.

           [EAGAIN]       The system-imposed limit on the total number of
                          processes under execution by a single user would
                          be exceeded.

           [ENOMEM]       There is insufficient swap space and/or physical
                          memory available in which to create the new
                          process.

 WARNINGS
      Standard I/O streams (see stdio(3S)) are duplicated in the child.



 Hewlett-Packard Company            - 2 -     HP-UX Release 9.0: August 1992






 fork(2)                                                             fork(2)





      Therefore, if fork is called after a buffered I/O operation without
      first closing or flushing the associated standard I/O stream (see
      fclose(3S)), the buffered input or output might be duplicated.

 AUTHOR
      fork() was developed by AT&T, the University of California, Berkeley,
      and HP.

 SEE ALSO
      acct(2), chroot(2), exec(2), exit(2), fcntl(2), getgroups(2),
      lockf(2), nice(2), plock(2), profil(2), ptrace(2), rtprio(2),
      semop(2), setuid(2), setpgrp(2), shmop(2), times(2), ulimit(2),
      umask(2), vfork(2), wait(2), fclose(3S), stdio(3S), acct(4),
      signal(5).

 STANDARDS CONFORMANCE
      fork(): AES, SVID2, XPG2, XPG3, XPG4, FIPS 151-2, POSIX.1





































 Hewlett-Packard Company            - 3 -     HP-UX Release 9.0: August 1992