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Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!athena.mit.edu!jik
From: jik@athena.mit.edu (Jonathan I. Kamens)
Newsgroups: comp.unix.questions,comp.unix.wizards
Subject: Re: system() --- the C function from hell?
Keywords: system, unix, question, does anyone use this line?
Message-ID: <10965@bloom-beacon.MIT.EDU>
Date: 30 Apr 89 11:23:05 GMT
References: <1827@uop.edu>
Sender: daemon@bloom-beacon.MIT.EDU
Reply-To: jik@athena.mit.edu (Jonathan I. Kamens)
Followup-To: comp.unix.questions
Organization: Massachusetts Institute of Technology
Lines: 58

In article <1827@uop.edu> jeff@uop.edu (Jeff Ferguson) writes:
>	Hi kids,
>
>	The system() call seems to wreak havoc with integer variables.
>I have the following code:

Since you have failed to provide all of the relevant code, most
specifically the declaration of the variable str, I can't tell you for
sure what is wrong, but I can tell you that it has nothing to do with
system, and I can also tell you that what I suspect is wrong is that
you are not allocated enough space for str so that your sprintf is
overwriting your integer variables (You declared str to be "char *,"
perhaps?).  Here's your sample code in a simple program wrapper and a
sample run of it that works:

		      *************************

#include <stdio.h>

main()
{
     int hip, lowp;
     char str[50];

     fprintf(stdout, "Enter hip: ");
     fflush(stdout);
     scanf("%d", &hip);

     fprintf(stdout, "Enter lowp: ");
     fflush(stdout);
     scanf("%d", &lowp);

     sprintf(str, "/bin/mkdir directory");
     system(str);

     fprintf(stdout, "lowp = %d, hip = %d\n", lowp, hip);
}

		      *************************

oliver% a.out
Enter hip: 3
Enter lowp: 3
lowp = 3, hip = 3
oliver% ls -d directory
directory/
oliver%

		      *************************

Jonathan Kamens			              USnail:
MIT Project Athena				410 Memorial Drive, No. 223F
jik@Athena.MIT.EDU				Cambridge, MA 02139-4318
Office: 617-253-4261			      Home: 617-225-8218

P.S. I have directed follow-ups to comp.unix.questions, as you should
have done.  Did this really need to go to comp.unix.wizards in the
first place?