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Re: do I need strcmp ?

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In <4eb4605c$0$20319$bbae4d71@news.suddenlink.net> "Bill Cunningham" <nospam@nspam.invalid> writes:

>     I am doing a comparison here and the code works and then doesn't work. 
> My goal is to start a string to be recognized by a function only if it 
> starts with a +. Kind of like cpp doesn't recognize preprocessor commands 
> unless # is present.

> #include <stdio.h>
> #include <string.h>

> int main()
> {
>     char *plus;
>     char *string = "+ hello there\n";
>     plus = strchr(string, '+');
>     if ((int) plus[0] == '+')
>  printf("ok\n");
>     if ((int) plus[0] != '+')
>  printf("no\n");
> }

> This code as it is works marvelously when finding + in a string. If 
> something other than + is used, I do not get no but a segmentation fault. Is 

That's because strchr returns NULL when the target character is not found,
which causes 'plus' to have a null value.  Then, when you attempt to
look at plus[0], the program crashes.

> the only way around this to use strcmp to see if the first character of the 
> string is + or not? Can the code be changed to accomplish what I want 
> without using strcmp?

Using strchr seems like overkill in this case.  You don't even need the
'plus' variable.  Just look for the character directly:

  char *string = "+hello there\n";

  if(string[0] == '+')
    printf("ok\n");
  else
    printf("no\n");

-- 
John Gordon                   A is for Amy, who fell down the stairs
gordon@panix.com              B is for Basil, assaulted by bears
                                -- Edward Gorey, "The Gashlycrumb Tinies"

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Thread

do I need strcmp ? "Bill Cunningham" <nospam@nspam.invalid> - 2011-11-04 17:59 -0500
  Re: do I need strcmp ? John Gordon <gordon@panix.com> - 2011-11-04 22:16 +0000
    Re: do I need strcmp ? "Bill Cunningham" <nospam@nspam.invalid> - 2011-11-04 18:20 -0500
  Re: do I need strcmp ? Martin Ambuhl <mambuhl@earthlink.net> - 2011-11-04 18:36 -0400
    Re: do I need strcmp ? Nick Keighley <nick_keighley_nospam@hotmail.com> - 2011-11-06 15:05 -0800
      Re: do I need strcmp ? Keith Thompson <kst-u@mib.org> - 2011-11-06 15:25 -0800

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