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From: stevesu@azure.UUCP (Steve Summit)
Newsgroups: net.unix-wizards
Subject: Re: "swapfd" (more unix ideas)
Message-ID: <288@azure.UUCP>
Date: Fri, 28-Jun-85 01:26:46 EDT
Article-I.D.: azure.288
Posted: Fri Jun 28 01:26:46 1985
Date-Received: Sun, 23-Jun-85 03:18:33 EDT
References: <6954@ucbvax.ARPA> <5687@utzoo.UUCP>
Organization: Tektronix, Beaverton OR
Lines: 22

> 1) have a swapfd system call
>         Usage:  swapfd(fd1,proc,fd2)
> or possibly:    swapfd(proc1,fd1,proc2,fd2)
> 
> what this does, is makes procs (usually another process) fd2, to become
> my fd1, and my fd1 to become (point to a file structure) of procs fd2.

I don't know if it's what the original submittor had in mind, but
the reason I've thought a call like this would be neat is because
you could use it to give a shell the ability to manipulate i/o
"after the fact," just like job control lets you manipulate
backgroundness/foregroundness "after the fact."  Is that command
taking too long?  Type control-Z and background it.  Don't want
the output coming out asysynchronously?  Well, I haven't thought
of a syntax, but the idea is that you want to reconnect the
standard output of the process to a file.  It gets hard if the
process in question has played with its file descriptors, like
repoening file descriptor 1 as something else, or dup'ing file
descriptor 1 to some other file descriptor and then using it
there.  It gets messy.
                                         Steve Summit
                                         tektronix!tekmdp!stevesu