bin/105721: Misleading error message from e.g. "df -l -t ufs"

[Fabian Ruch]

The following reply was made to PR bin/105721; it has been noted by GNATS.

From: Fabian Ruch <Fabian.Ruch at gmx.de>
To: bug-followup at FreeBSD.org,  john at jnielsen.net
Cc:  
Subject: Re: bin/105721: Misleading error message from e.g. "df -l -t ufs"
Date: Tue, 28 Nov 2006 16:46:59 +0100

 A short time ago I contacted the submitter John Nielsen. Now he 
 suggested that I send a similar mail as followup. This is my first look 
 at a problem report as you probably can see when looking at my "fix" 
 (works out, but maybe doesn't please you). Please give me feedback and 
 tell me what to do better next time.
 
 When there are filesystems not mounted locally df should report an error 
 if the '-l' and '-t' arguments are specified at the same time. But the 
 correct error ("-l and -t are mutually exclusive.") is only mentioned if 
 you specify the '-t' argument before the '-l' one. Otherwise df thinks 
 '-t' is specified twice ("only one -t option may be specified").
 Another problem can be discussed. Shall df break if the '-l' argument is 
 specified but it doesn't effect anything? df behaves in the same 
 situation in different ways depending on the order the arguments appear. 
 For example if '-l' specified first df ignores this and goes on. In 
 contrast df breaks if '-l' is specified after '-t' ("-l and -t are 
 mutually exclusive."). This should be displayed in both cases or in none 
 of both.
 
 Now there is more than one way to solve the problem. We could declare 
 another flag variable (to tell df that '-l' is specified). Another way 
 is to check whether '-l' effects df's work.
 The added Fix does declare another flag variable (no great work, I 
 know). df will break at to points. The first breakpoint is when the '-t' 
 argument is specified twice and '-l' isn't specified at this time. The 
 second breakpoint is when '-t' and '-l' are specified at the same time.
 
 Regards,
     Fabian
 
 --
 
   --- df.c        Mon Jan 10 09:39:21 2005
   +++ df.c        Sun Nov 26 17:59:04 2006
   @@ -93,7 +93,7 @@
           return (a > b ? a : b);
    }
 
   -static int     aflag = 0, cflag, hflag, iflag, nflag;
   +static int     aflag = 0, lflag = 0, cflag, hflag, iflag, nflag;
    static struct  ufs_args mdev;
 
    int
   @@ -147,8 +147,9 @@
                           hflag = 0;
                           break;
                   case 'l':
   -                       if (vfslist != NULL)
   +                       if (!lflag && vfslist != NULL)
                                   errx(1, "-l and -t are mutually 
 exclusive.");
   +                       lflag = 1;
                           vfslist = makevfslist(makenetvfslist());
                           break;
                   case 'm':
   @@ -159,7 +160,9 @@
                           nflag = 1;
                           break;
                   case 't':
   -                       if (vfslist != NULL)
   +                       if (lflag)
   +                               errx(1, "-l and -t are mutually 
 exclusive.");
   +                       else if (vfslist != NULL)
                                   errx(1, "only one -t option may be 
 specified");
                           fstype = optarg;
                           vfslist = makevfslist(optarg);