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Re: [command line arguments] more elegant solution ??

From BartC <bc@freeuk.com>
Newsgroups comp.lang.c
Subject Re: [command line arguments] more elegant solution ??
Date 2016-12-11 23:43 +0000
Organization A noiseless patient Spider
Message-ID <o2ko86$jgi$1@dont-email.me> (permalink)
References <f5132d7e-048b-4115-ad9e-4f5cfa8533e7@googlegroups.com> <o2k5rm$t8h$1@dont-email.me> <871sxew6n8.fsf@bsb.me.uk>

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On 11/12/2016 20:30, Ben Bacarisse wrote:
> BartC <bc@freeuk.com> writes:
> <snip>
>
>> (Testing the third argument is a number is the only tricky bit. You
>> might try converting it to a number using atol, converting back to a
>> string using sprintf, and comparing that string with argv[2].)
>
> That does not always work (as I am sure you know) because there may be
> leading space,

Leading spaces are unlikely in this case.

  a sign, zeros etc.  The simplest "student" solution is
> probably just
>
>   sscanf(argv[i], "%d", &num) == 1
>
> For the test you ignore num, but it's likely that a later version will
> actually use it.  A neat use of scanf failing to match input allows you
> test the whole string:
>
>   sscanf(argv[i], "%d %c", &num, &ch) == 1
>
> If the number is followed by anything other than white-space characters,
> the result will be 2 not 1.

I don't know all the intricacies of sscanf.

But there is one thing that only occurs under Linux that could screw 
things up (not here because there will be at least two other files).

If the 3rd parameter is *, and there happens to be one file in the 
directory with a numeric name, such as 9177, that will then appear as a 
valid argument. (You may have noticed a big thread in the python group 
about this.)

Even here, it's hard to completely rule out someone typing something 
with * or ? as the second argument, and ending up with input that passes 
the test, depending on some random pattern of filenames.

However the OP mustn't worry about this... (it's just a Linux quirk).

-- 
Bartc

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Thread

[command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 07:56 -0800
  Re: [command line arguments] more elegant solution ?? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-11 16:47 +0000
    Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 09:16 -0800
      Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 09:26 -0800
        Re: [command line arguments] more elegant solution ?? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-11 19:05 +0000
          Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 11:15 -0800
            Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 11:53 -0800
              Re: [command line arguments] more elegant solution ?? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-11 20:03 +0000
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 12:26 -0800
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 12:33 -0800
                Re: [command line arguments] more elegant solution ?? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-11 20:33 +0000
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 12:35 -0800
                Re: [command line arguments] more elegant solution ?? "James R. Kuyper" <jameskuyper@verizon.net> - 2016-12-11 16:06 -0500
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 13:11 -0800
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 13:20 -0800
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 13:25 -0800
                Re: [command line arguments] more elegant solution ?? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-11 21:32 +0000
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 13:44 -0800
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 13:47 -0800
                Re: [command line arguments] more elegant solution ?? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-11 21:56 +0000
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 14:04 -0800
                Re: [command line arguments] more elegant solution ?? Robert Spanjaard <spamtrap@arumes.com> - 2016-12-11 23:07 +0100
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 14:15 -0800
                Re: [command line arguments] more elegant solution ?? Robert Spanjaard <spamtrap@arumes.com> - 2016-12-11 23:32 +0100
                Re: [command line arguments] more elegant solution ?? jameskuyper@verizon.net - 2016-12-11 14:42 -0800
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 14:52 -0800
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 14:40 -0800
                Re: [command line arguments] more elegant solution ?? jameskuyper@verizon.net - 2016-12-11 14:55 -0800
                Re: [command line arguments] more elegant solution ?? "James R. Kuyper" <jameskuyper@verizon.net> - 2016-12-11 19:44 -0500
                Re: [command line arguments] more elegant solution ?? Richard Heathfield <rjh@cpax.org.uk> - 2016-12-11 23:20 +0000
                Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 15:28 -0800
                Re: [command line arguments] more elegant solution ?? jameskuyper@verizon.net - 2016-12-11 16:28 -0800
      Re: [command line arguments] more elegant solution ?? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-11 18:57 +0000
  Re: [command line arguments] more elegant solution ?? Barry Schwarz <schwarzb@dqel.com> - 2016-12-11 10:04 -0800
    Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 11:25 -0800
  Re: [command line arguments] more elegant solution ?? BartC <bc@freeuk.com> - 2016-12-11 18:29 +0000
    Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 11:25 -0800
    Re: [command line arguments] more elegant solution ?? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-11 20:30 +0000
      Re: [command line arguments] more elegant solution ?? BartC <bc@freeuk.com> - 2016-12-11 23:43 +0000
        Re: [command line arguments] more elegant solution ?? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2016-12-11 19:02 -0500
          Re: [command line arguments] more elegant solution ?? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2016-12-11 19:13 -0500
            Re: [command line arguments] more elegant solution ?? BartC <bc@freeuk.com> - 2016-12-12 00:55 +0000
              Re: [command line arguments] more elegant solution ?? BartC <bc@freeuk.com> - 2016-12-12 01:02 +0000
                Re: [command line arguments] more elegant solution ?? Keith Thompson <kst-u@mib.org> - 2016-12-11 19:02 -0800
                Re: [command line arguments] more elegant solution ?? BartC <bc@freeuk.com> - 2016-12-12 11:50 +0000
                Re: [command line arguments] more elegant solution ?? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-12 13:46 +0000
                Re: [command line arguments] more elegant solution ?? BartC <bc@freeuk.com> - 2016-12-12 14:43 +0000
                Re: [command line arguments] more elegant solution ?? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-12 22:09 +0000
                Re: [command line arguments] more elegant solution ?? Keith Thompson <kst-u@mib.org> - 2016-12-12 08:58 -0800
              Re: [command line arguments] more elegant solution ?? Lew Pitcher <lew.pitcher@digitalfreehold.ca> - 2016-12-11 20:06 -0500
              Re: [command line arguments] more elegant solution ?? jameskuyper@verizon.net - 2016-12-11 17:37 -0800
              Re: [command line arguments] more elegant solution ?? Keith Thompson <kst-u@mib.org> - 2016-12-11 18:59 -0800
        Re: [command line arguments] more elegant solution ?? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2016-12-12 02:47 +0000
  Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-11 15:11 -0800
  Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-12 00:25 -0800
  Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-12 00:27 -0800
    Re: [command line arguments] more elegant solution ?? Barry Schwarz <schwarzb@dqel.com> - 2016-12-12 01:01 -0800
      Re: [command line arguments] more elegant solution ?? Dexterr <dejangru@gmail.com> - 2016-12-12 09:42 -0800
        Re: [command line arguments] more elegant solution ?? "James R. Kuyper" <jameskuyper@verizon.net> - 2016-12-12 13:58 -0500
        Re: [command line arguments] more elegant solution ?? Barry Schwarz <schwarzb@dqel.com> - 2016-12-12 14:18 -0800

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