Reading characters other than letters or digits in C

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Following piece of code reads from a file and then prints output on the screen.

C++

#define _CRT_SECURE_NO_WARNINGS
#include "stdafx.h"
int main ()
{
	char c;
	int i;
	for (i=0; (c!=EOF); ++i)
	{
		c=getchar();
		printf("%c",c);
	}
}

When I execute .exe file and redirect the input to ReadMe.txt and output to tmp.txt by giving following command in cmd:

file.exe < ReadMe.txt > tmp.txt

program prints a funny character at the end of the file i.e., ÿ. To avoid this I want to mention the range of valid character in the loop which means program should terminate if any character outside this range hits the loop iteration. I know,

Letters range::- 'a' to 'z' , 'A' to 'Z'

(c<'A') && (c>'Z') && (c<'a') && (c>'z')

Digits range::- '0' to '9'

(c<'0') && (c>'9')

Now I want the range of other characters i.e., ~!@#$%^&*()-+=_[]{}\|:;"'<>,.?/

I was wondering if someone can help me in that.

Posted 15-Aug-14 1:46am

rf_libra

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OriginalGriff · Accepted Answer · 2014-08-15T01:56:00

Solution 1

Not quite what you want: 'A' is less that 'Z' and less than 'a'!

C++

if ( ((c >= 'A') && (c <= 'Z')) || ((c >= 'a') && (c <= 'z')))
   {
   // It's an Alpha
   }

C++

if ((c >= '0') && (c <= '9'))
   {
   // It's an Digit
   }

And you can check for the other print able characters quite easily.
But...

C++

if ((c >= ' ') && (c <= '~'))
   {
   // It's printable.
   }

Might be easier.

Posted 15-Aug-14 1:56am

OriginalGriff

Comments

[no name] 15-Aug-14 8:01am

Sorry @OriginalGriff, I didn't get what you said. ('A' is less than 'Z') ?

OriginalGriff 15-Aug-14 8:06am

Oh yes. Characters have an "order" in whatever encoding you use: ASCII, Unicode, even EBCDIC.
For ASCII (and also Unicode, but it's a lot bigger:
http://www.asciitable.com/index/asciifull.gif
For a "standard" text file, you can treat anything below space or above tilde as "unprintable"

[no name] 15-Aug-14 8:19am

@OriginalGriff , I modified the original code as:

#define _CRT_SECURE_NO_WARNINGS
#include "stdafx.h"

int main ()
{
char c;
int i;
for (i=0; (c!=EOF); ++i)
{
c=getchar();
if ( ((c <= 'A') && (c >= 'Z')) || ((c <= 'a') && (c >= 'z')))
{
c='%';
}
if ((c <= '0') && (c >= '9'))
{
c='%';
}
if ((c <= ' ') && (c >= '~'))
{
c='%';
}
printf("%c",c);
}
}
I'm still not able to get rid of this funny character (ÿ). It still gets printed at the end of output file.

OriginalGriff 15-Aug-14 8:39am

Um.
Did you read what I wrote, at all?
Is something is not A-Z or a-z, it will never pass your digit check.
Try the last way I showed you, and if it is printable, print it. Otherwise, do nothing.