Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > comp.lang.c > #42403

Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead?

Show all headers | View raw

rivkaumiller@gmail.com writes:
> How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead?
>
> For example, compact while loops are written like this in k&r
>
> while ((c=getchar())!=NULL){
>
>   // do certain actions
>
> }

NULL is a null pointer constant.  getchar() returns EOF when it's unable
to read a character.  And be sure that "c" is defined as an int, not as
a char.

> and I want to convert a stanza like
>
> fscanf ( FpSource, "%d" , &input );
> while (input != EOF){
>
>   // do certain actions
>
>   fscanf ( FpSource, "%d" , &input );
> }
>
> into the above form with getchar() so that there is a single instance of fscanf.

To use any input function, you need to understand the value that it
returns.

getchar() returns the value of the character it just read from stdin,
treated as an unsigned char and converted to int (for typically systems,
it will be a value in the range 0..255).  That's if it's able to read a
character.  If it's not, either because there are no more characters to
be read or because there was an error, it returns EOF, which is a
negative int value (typically -1, but don't assume that).

fscanf(), if it's successful, returns the number of items it read.
For

    fscanf(FpSource, "%d" , &input);

it returns 1 if it was able to read an int value into "input".

If an input failure occurs, it returns EOF.  Otherwise, it returns the
number of items it was able to read, which in this case will be either 0
or 1.  (It's 0 if the input doesn't match the syntax of an optionally
signed decimal integer.)

That, along with the other followups, should be enough information get
you going.

Note that comparing the value of input to EOF doesn't make much sense;
input==EOF doesn't say anything meaningful about the input.

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for JetHead Development, Inc.
"We must do something.  This is something.  Therefore, we must do this."
    -- Antony Jay and Jonathan Lynn, "Yes Minister"

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

Thread

How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? rivkaumiller@gmail.com - 2014-03-30 19:04 -0700
  Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Richard Damon <Richard@Damon-Family.org> - 2014-03-30 22:31 -0400
    Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? rivkaumiller@gmail.com - 2014-03-30 19:43 -0700
      Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Richard Damon <Richard@Damon-Family.org> - 2014-03-30 23:09 -0400
  Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? rivkaumiller@gmail.com - 2014-03-30 19:35 -0700
  Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? rivkaumiller@gmail.com - 2014-03-30 19:47 -0700
    Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? "BartC" <bc@freeuk.com> - 2014-03-31 11:53 +0100
      Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-03-31 17:50 +0000
        Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Kaz Kylheku <kaz@kylheku.com> - 2014-03-31 18:55 +0000
          Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? "BartC" <bc@freeuk.com> - 2014-03-31 22:51 +0100
            Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Kaz Kylheku <kaz@kylheku.com> - 2014-03-31 22:46 +0000
              Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? "BartC" <bc@freeuk.com> - 2014-04-01 00:03 +0100
              Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-03-31 20:33 -0400
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? "BartC" <bc@freeuk.com> - 2014-04-01 09:35 +0100
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Keith Thompson <kst-u@mib.org> - 2014-04-01 07:35 -0700
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? "BartC" <bc@freeuk.com> - 2014-04-01 17:19 +0100
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Keith Thompson <kst-u@mib.org> - 2014-04-01 10:14 -0700
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? "BartC" <bc@freeuk.com> - 2014-04-01 18:59 +0100
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Öö Tiib <ootiib@hot.ee> - 2014-04-04 00:29 -0700
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? "BartC" <bc@freeuk.com> - 2014-04-04 12:35 +0100
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Seungbeom Kim <musiphil@bawi.org> - 2014-04-08 11:48 -0700
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Öö Tiib <ootiib@hot.ee> - 2014-04-08 15:52 -0700
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-02 18:38 +0000
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Keith Thompson <kst-u@mib.org> - 2014-04-02 11:48 -0700
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-02 23:18 +0000
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Kaz Kylheku <kaz@kylheku.com> - 2014-04-03 00:05 +0000
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? James Kuyper <jameskuyper@verizon.net> - 2014-04-02 21:12 -0400
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Keith Thompson <kst-u@mib.org> - 2014-04-02 19:16 -0700
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-03 03:16 +0000
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? James Kuyper <jameskuyper@verizon.net> - 2014-04-02 15:07 -0400
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Ben Bacarisse <ben.usenet@bsb.me.uk> - 2014-04-01 23:00 +0100
                Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Seungbeom Kim <musiphil@bawi.org> - 2014-04-08 11:56 -0700
            Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Phil Carmody <thefatphil_demunged@yahoo.co.uk> - 2014-04-01 02:14 +0300
            Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? glen herrmannsfeldt <gah@ugcs.caltech.edu> - 2014-04-01 04:52 +0000
              Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? "BartC" <bc@freeuk.com> - 2014-04-01 09:56 +0100
  Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Eric Sosman <esosman@comcast-dot-net.invalid> - 2014-03-30 22:49 -0400
  Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? James Kuyper <jameskuyper@verizon.net> - 2014-03-30 22:58 -0400
    Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? rivkaumiller@gmail.com - 2014-03-31 09:10 -0700
      Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? James Kuyper <jameskuyper@verizon.net> - 2014-03-31 12:25 -0400
      Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Keith Thompson <kst-u@mib.org> - 2014-03-31 10:56 -0700
  Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? James Kuyper <jameskuyper@verizon.net> - 2014-03-30 23:09 -0400
  Re: How to modify ((c=getchar())!=NULL) to use fscanf or scanf instead? Keith Thompson <kst-u@mib.org> - 2014-03-31 08:55 -0700

csiph-web