AT&T UNIX™PC Unix System V Users Manual - tenox

FORK(2) FORK(2)
NAME
fork - create a new process
SYNOPSIS
int fork ()
DESCRIPTION
Fork causes creation of a new process. The new process (child
process) is an exact copy of the calling process (parent process).
This means the child process inherits the following attributes from
the parent process:
environment
close-on-exec flag (see exec(2))
signal handling settings (i.e., SIG_DFL, SIG_ING, function
address)
set-user-ID mode bit
set-group-ID mode bit
profiling on/off status
nice value (see nice(2))
all attached shared memory segments (see shmop(2))
process group ID
tty group ID (see exit(2) and signal(2))
trace flag (see ptrace(2) request 0)
current working directory
root directory
file mode creation mask (see umask(2))
file size limit (see ulimit(2))
The child process differs from the parent process in the following
ways:
The child process has a unique process ID.
The child process has a different parent process ID (i.e.,
the process ID of the parent process).
The child process has its own copy of the parent's file
descriptors. Each of the child's file descriptors shares a
common file pointer with the corresponding file descriptor
of the parent.
All semadj values are cleared (see semop (2)).
Process locks, text locks and data locks are not inherited
by the child (see plock(2)).
The child process's utime, stime, cutime, and cstime are
set to 0.
The child process has a different amount of time left until
an alarm clock signal (see alarm(2)).
Fork will fail and no child process will be created if one or more
of the following are true:
The system-imposed limit on the total number of
processes under execution would be exceeded. [EAGAIN[
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