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FORK(2V)                                                              FORK(2V)



NAME
       fork - create a new process

SYNOPSIS
       int fork()

SYSTEM V SYNOPSIS
       pid_t fork()

DESCRIPTION
       fork()  creates  a  new process.  The new process (child process) is an
       exact copy of the calling process except for the following:

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

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

       o  The child process has its own  copy  of  the  parent's  descriptors.
          These  descriptors  reference  the same underlying objects, so that,
          for instance, file pointers in file objects are shared  between  the
          child  and  the parent, so that an lseek(2V)) on a descriptor in the
          child process can affect a subsequent read(2V) or write(2V)  by  the
          parent.  This descriptor copying is also used by the shell to estab-
          lish standard input and output for newly created processes  as  well
          as to set up pipes.

       o  The  child  process  has its own copy of the parent's open directory
          streams (see directory(3V)).  Each  open  directory  stream  in  the
          child  process  shares  directory stream positioning with the corre-
          sponding directory stream of the parent.

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

       o  The child processes resource utilizations are set to  0;  see  getr-
          limit(2).   The  it_value and it_interval values for the ITIMER_REAL
          timer are reset to 0; see getitimer(2).

       o  The   child   process's   values   of   tms_utime(),    tms_stime(),
          tms_cutime(), and tms_cstime() (see times(3V)) are set to zero.

       o  File  locks  (see  fcntl(2V))  previously  set by the parent are not
          inherited by the child.

       o  Pending alarms (see alarm(3V)) are cleared for the child process.

       o  The set of signals pending for the child  process  is  cleared  (see
          sigvec(2)).

RETURN VALUES
       On  success,  fork()  returns  0  to  the child process and returns the
       process ID of the child process to the  parent  process.   On  failure,
       fork()  returns  -1  to  the parent process, sets errno to indicate the
       error, and no child process is created.

ERRORS
       fork() will fail and no child process will be created if one or more of
       the following are true:

       EAGAIN         The  system-imposed  limit  on  the total number of pro-
                      cesses under execution would be exceeded.  This limit is
                      determined when the system is generated.

                      The  system-imposed  limit  on  the total number of pro-
                      cesses  under  execution  by  a  single  user  would  be
                      exceeded.   This  limit is determined when the system is
                      generated.

       ENOMEM         There is insufficient swap space for the new process.

SEE ALSO
       execve(2V), getitimer(2), getrlimit(2), lseek(2V), read(2V),  semop(2),
       wait(2V), write(2V)



                                21 January 1990                       FORK(2V)