Groups | Search | Server Info | Login | Register

Groups > comp.lang.c.moderated > #445

Re: Convert string to C expression syntax

Show all headers | View raw

On Tue, 30 Jul 2013 21:58:38 -0500 (CDT), nilay <nilaybhatt@gmail.com>
wrote:

>Hi,
>I want to do the following,
>
>==========================================
>int main(int argc, char *argv[])
>{
>    ...
>    if (*argv[1]) 
>    {
>      ...
>    }
>    ...
>}
>==========================================
>
>as i tried to show above, I want to pass a filter condition
>at command-line input. And I want to convert that input string
>to 'if-condition expression' so that it can be used in the program.
>How can it be done?? I am struggling very hard to get it right.

It depends on what type of condition you want to check for.

If you want to check if the string exists, you would actually check
argc.  C does not support omitted command line arguments except at the
end.

If you want to check for an empty string (and your system allows you
to specify one as a command line argument), then the code you posted
will check that.  An empty string is an array of 1 char and that char
has the value '\0'.  Your code evaluates the first char in the array
pointed to by argv[1].

If you want to check whether the string has a certain value, you would
use strcmp or strncmp in the condition of your if statement. Something
along the lines of 
     if (!strcmp(argv[1], "ABC")
          {/* equal code */}
     else
          {/* optional not equal code */}

-- 
Remove del for email
-- 
comp.lang.c.moderated - moderation address: clcm@plethora.net -- you must
have an appropriate newsgroups line in your header for your mail to be seen,
or the newsgroup name in square brackets in the subject line.  Sorry.

Back to comp.lang.c.moderated | Previous | Next — Previous in thread | Next in thread | Find similar

Thread

Convert string to C expression syntax nilay <nilaybhatt@gmail.com> - 2013-07-30 21:58 -0500
  Re: Convert string to C expression syntax James Kuyper <jameskuyper@verizon.net> - 2013-07-31 21:22 -0500
  Re: Convert string to C expression syntax Barry Schwarz <schwarzb@dqel.com> - 2013-07-31 21:22 -0500
    Re: Convert string to C expression syntax Keith Thompson <kst-u@mib.org> - 2013-08-01 12:58 -0500
      Re: Convert string to C expression syntax Ike Naar <ike@ukato.freeshell.org> - 2013-08-01 21:05 -0500
        Re: Convert string to C expression syntax Keith Thompson <kst-u@mib.org> - 2013-08-02 18:34 -0500
  Re: Convert string to C expression syntax gordonb.uvkjx@burditt.org (Gordon Burditt) - 2013-07-31 21:22 -0500
  Re: Convert string to C expression syntax Roberto Waltman <usenet@rwaltman.com> - 2013-08-05 11:24 -0500
  Re: Convert string to C expression syntax malcolm.mclean5@btinternet.com - 2013-09-02 04:09 -0500
  Re: Convert string to C expression syntax "Paul D. DeRocco" <pderocco@ix.netcom.com> - 2013-09-06 23:25 -0500
    Re: Convert string to C expression syntax James Kuyper <jameskuyper@verizon.net> - 2013-09-11 17:27 -0500
      Re: Convert string to C expression syntax "Paul D. DeRocco" <pderocco@ix.netcom.com> - 2013-09-12 11:34 -0500
      Re: Convert string to C expression syntax Francis Glassborow <francis.glassborow@btinternet.com> - 2013-09-12 11:38 -0500
  Re: Convert string to C expression syntax Nitin Tripathi <2nitintr@gmail.com> - 2013-09-11 17:31 -0500

csiph-web