V1/man/man2/wait.2

        11/3/71                                                SYS WAIT (II)


NAME              wait -- wait for process to die

SYNOPSIS          sys      wait                / wait = 7.
                  (process ID in r0)

DESCRIPTION       wait causes its caller to delay until one of its child processes
                  terminates. If any child has already died, return is immediate; if
                  there are no children, return is immediate with the error bit set. In
                  the case of several children several waits are needed to learn of all
                  the deaths.

FILES

SEE ALSO          fork

DIAGNOSTICS       error bit (c--bit) on if no children not previously waited for.

BUGS              A child which dies but is never waited for is not really gone in that
                  it still consumes disk swap and system table space. This can make it
                  impossible to create new processes. The bug can be noticed when
                  several & separators are given to the shell not followed by an
                  command without an ampersand. Ordinarily things clean themselves up
                  when an ordinary command is typed, but it is possible to get into a
                  situation in which no commands are accepted, so no waits are done;
                  the system is then hung.

                  The fix, probably, is to have a new kind of fork which creates a
                  process for which no wait is necessary (or possible); also to limit
                  the number of active or inactive descendants allowed to a process.

OWNER             ken, dmr