CODEWITHSUNDEEP
cnewline
user2263800
user2263800

Reputation: 303

c K&R count newlines, tabs and spaces

I'm attempting exercise 1-8 in the K&R book but having an issue with the amount of newlines being found:

Write a program to count blanks, tabs and newlines.

#include <stdio.h>

main()
{
    int c, nl, tabs, blanks;

    nl, tabs, blanks = 0;
    while ((c = getchar()) != EOF)
    {
            if (c == '\n')
                    ++nl;
                    printf("%d\n", nl);
            if (c == ' ')
                    ++blanks;
            if (c == '\t')
                    ++tabs;
    }
    printf("\n Blanks: %d\nNewlines: %d\nTabs: %d\n\n", blanks, nl, tabs);
}

I run the program on itself and the output I receive is:

Blanks: 32 
Newlines: -1216989677
Tabs: 25

Why is this happening? My first thought was that it could be the minimum possible number of an integer but I checked and I don't believe its that.

Upvotes: 2

Views: 189

Answers (3)

Deduplicator
Deduplicator

Reputation: 45654

You did not initialize nl and tabs, so your program has undefined behavior.

nl, tabs, blanks = 0;

only initializes blanks. It should be

nl = tabs = blanks = 0;

There's one more error: Neither programmer intent nor indentation defines blocks, only curly braces {} do:

if (c == '\n')
    ++nl;
printf("%d\n", nl);

I corrected the indentation of the block to make the error obvious. Not quite what you wanted, so use curly braces to group the two statements as one block.

Anyway, consider writing C89 without deprecated compatibility features or even better C11.
That means you have to provide proper prototypes. Possible ones for main:

int main(void)
int main(int argc, char *argv[])

Also, enable more warnings, and strive for warning-free compilation: -Wall -Wextra
Doing so (including reading and acting on the warnings) will help you identify and correct many errors the easy way.

Upvotes: 3

hdante
hdante

Reputation: 8020

nl = tabs = blanks = 0;

Compile with -Wall and you'll see the error:

cc -Wall -c a.c
(...)    
a.c:4:4: warning: left-hand operand of comma expression has no effect [-Wunused-value]
a.c:4:7: warning: left-hand operand of comma expression has no effect [-Wunused-value]

Upvotes: 3

CS Pei
CS Pei

Reputation: 11047

Change this line nl, tabs, blanks = 0; to 

    nl=tabs= blanks = 0;

Upvotes: 2

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