.th fork IV 4/21/86
.sh NAME
fork  -  spawn new process
.sh SYNOPSIS
.ft B
fork( )
.ft R
.sh DESCRIPTION
Fork is the only way new processes are created.  The new process's core
image is a copy of that of the caller of fork.  The only distinction is
the return location and the fact that r0 in the old (parent) process
contains the process ID of the new (child) process.  This process ID is
used by wait.
.s3
The two returning processes share all open files that existed before
the call.  In particular, this is the way that standard input and
output files are passed and also how pipes are set up.
.s3
From C, the child process receives a 0 return, and the parent receives
a non-zero number which is the process ID of the child; a return of -1
indicates inability to create a new process.
.sh "SEE ALSO"
wait (IV), execv (IV)
.sh DIAGNOSTICS
The error bit (c-bit) is set in the old process if a new process could
not be created because of lack of process space.  From C, a return of
-1 (not just negative) indicates an error.

