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Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!mit-eddie!mit-amt!mit-caf!vlcek
From: vlcek@mit-caf.MIT.EDU (Jim Vlcek)
Newsgroups: comp.lang.c,comp.unix.wizards
Subject: Re: redirect stdin when using execl
Message-ID: <2489@mit-caf.MIT.EDU>
Date: 11 Jun 89 03:48:31 GMT
References: <851@pcsbst.UUCP> <5587@goofy.megatest.UUCP>
Reply-To: vlcek@mit-caf.UUCP (Jim Vlcek)
Organization: Microsystems Technology Laboratories, MIT
Lines: 22

In article <5587@goofy.megatest.UUCP> djones@megatest.UUCP (Dave Jones) writes:
>> In article <414@sc50.UUCP> ron@sc50.UUCP ( Ron Winnacott ) writes:
>>>Can anyone tell me how to redirect stdin when I use execl to 
>>>start a new program.
>
>Under BSD Unix, you use dup2. 

plus a bit of code showing how to fork(), dup2(), and then execl() to
get the desired effect.

I think a much better way, under BSD, is to use freopen() to attach
stdin to the redirected file.  Such redirection is, in fact, precisely
the intended usage of this function call.  Is freopen() a Berklism, or
do you have that in Sys V as well?  I'm almost completely unfamiliar
with the latter.

The original example, passing the string "<" and the redirected file,
was so innocently misguided I really got a laugh out of it.
execl()'ing "/bin/sh" to parse the command, or using system(), on the
other hand, were somewhat less amusing.

Jim Vlcek  (vlcek@caf.mit.edu  uunet!mit-caf!vlcek)