🚀 go-pugleaf

On 10 Jan 1999 21:55:16 GMT, "Dan Akunis" <akunis@glx.chief.co.il>
wrote:

> Here is the C code for your BASIC script:
> 
> #include<stdio.h>
> #include<conio.h>

There is no conio.h header in the C programming language.  It's OK to
discuss it in the Borland and MS-DOS newsgroups but it is off-topic in
alt.comp.lang.learn.c-c++.

> #include<string.h>
> 
> void main()
>   {
>     char x[50],text[50]="This is default text";
>     int  x1=0,amount=50;
>     printf("\n");
>     printf("Enter something if you like!  <%s> ",text);
>     gets(x);

Never NEVER NEVER use gets().  It is the most dangerous function in
the entire standard C library.  Using it is a mark of the
Klewless(tm).

What happens when the user types 51 characters into your 50 character
array?  Or 100?  Or 200?

Answer: BCD (Burn, Crash, Die).




>     if (strlen(x))

If gets() or most other string input functions fail, the contents of
the buffer are undefined, and might not represent a valid string.
This could cause strlen() to crash, particularly on a protected mode
operating system.

>       strcpy(text,x);
>     printf("Enter a value <%d> ",amount);
>     scanf("%d",&x1);
>     if (x1 != 0)
>       amount=x1;
>     printf("\n");
>     printf("The value of text$ now = %s\n",text);
>     printf("The amount = %d\n",amount);
>     getch();
>   }
> 
> mbt4w <DontlikeSpam@overthere.com> wrote in article
> <36990041.3BADD052@overthere.com>...
> > Hi,
> > 
> > I would like to allow defaults to user input in C. 
> > I'm using Borland C++ 4.52 on Win98. I'm trying to learn 
> > standard C programming or has close as possible even though 
> > I'm using a C++ package.   It seems the input commands I've 
> > tried so far will not allow an 'empty' entry. 
> > 
> > What I would like to happen is :
> > � Prompt the user for an input while displaying a default entry
> > � If the user presses only the enter key use the default entry
> > � If another value was entered, used it.
> > 
> > Below is a basic program that does this. 
> > How do I do it in C?
> > 
> > text$ = "This is default text"
> > amount = 50
> > PRINT
> > PRINT "Enter something if you like! <"; text$; "> ";
> > INPUT x$
> > IF x$ <> "" THEN text$ = x$
> > PRINT "Enter a value. <"; amount; "> ";
> > INPUT x
> > IF x <> 0 THEN amount = x
> > PRINT
> > PRINT "The value of text$ now = "; text$
> > PRINT "The amount ="; amount
> > 
> > 
> > Thanks
> > 

<Jack>

Dan's basic idea is sound, in that you evaluate the input in a second
variable and only replace the real value if the new one is good.

For a safe replacement for gets() which removes the '\n' at the end of
the string, see http://home.att.net/~jackklein/ctips01.html#safe_gets.

</Jack>
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