Xref: utzoo comp.unix.questions:31150 comp.lang.c:39141
Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!cs.utexas.edu!uunet!mcsun!ukc!ox-prg!msc7.comlab!imc
From: imc@prg.ox.ac.uk (Ian Collier)
Newsgroups: comp.unix.questions,comp.lang.c
Subject: Re: UNIX commands in C
Message-ID: <751.imc@uk.ac.ox.prg>
Date: 4 May 91 11:34:38 GMT
References: <1991Apr28.153127.24926@jack.sns.com> <24527@well.sf.ca.us> <REARL.91May1113957@nutrimat.gnu.ai.mit.edu>
Sender: news@prg.ox.ac.uk
Reply-To: imc@prg.ox.ac.uk (Ian Collier)
Organization: Oxford University Computing Laboratory, UK
Lines: 27

In article <REARL.91May1113957@nutrimat.gnu.ai.mit.edu>, rearl@gnu.ai.mit.edu (Robert Earl) wrote:
>In article <24527@well.sf.ca.us> ron@well.sf.ca.us (Ronald Hayden) writes:
>|   #include <stdio.h>
>|
>|   main ()
>|   {
>|    printf("\nTesting the UNIX 'who' command --\n");
>|    system("who");
>|    printf("\nDone.\n");
>|    exit(1);
>|   }

>Since system() [and popen()] does an implicit fork, it's good practice
>to explicitly flush output buffers before you call this routine;

[etc]

Also, that should really be "/bin/who" rather than just "who", unless
you are going to set the path explicitly in the program. Otherwise the
program could break on someone else's machine if they do not have /bin
in their path (unlikely) or if some other random program called "who"
appears before /bin/who in the path. If you do this in an suid program
be absolutely certain to specify the path, or else this creates a
security loophole.

Ian Collier
Ian.Collier@prg.ox.ac.uk | imc@ecs.ox.ac.uk