Thread: Program not printing the first and last string characters

Well I am almost done with this exercise where I had to print the longest line from a set of input lines.

Code:

#include <stdio.h>#include <stdlib.h>


#define MAX 1000


int main()
{
int len=0,i,j,c,k;
char line[MAX];
char longest[MAX];


while ((c = getchar())!= EOF)
{
    for(i=0,j=0 ; (c=getchar()) != '\n'; i++){
            line[i]=c;
            j++;}
    if(j>len){len = j;
                for(k=0;k<j-1;k++){
                longest[k]=line[k];
                }
}
}
printf("%d\n %s",len,longest);


}

There is just one problem. It leaves out the first and last character of the longest string. Where's my mistake?

You're throwing away the first char by reading it into c with the outer loop and then immediately reading another char into c with the inner loop.

You're leaving out the last char by only copying up to j - 2 (by using the condition k < j - 1).

Your j variable is useless since it mirrors i.

You have no buffer-overflow protection.

Your inner loop will become infinite if there's no newline after the last line in the file since you aren't testing for EOF there.

You need to zero-terminate longest if you're going to print if with printf (or use any other standard library functions that require zero-terminated strings).

And your spacing is terrible.

BTW, are you not allowed to use fgets and strcpy?

Code:

    while (fgets(line, sizeof line, stdin) != NULL))
        int sz = strlen(line);
        if (sz > len) {
            len = sz;
            strcpy(longest, line);
        }

I didn't see a statement like this before:

Code:

int len=0,i,j,c,k;

What's it doing?
I know this form:

Code:

int x=5;

Originally Posted by Salem

> int len=0,i,j,c,k;
> What's it doing?
Declaring 5 integer variables, but only initialising one one them to zero.
Do you know which variable ends up being zero?

I remembered it now, I think only len=0

So how to write the inner loop without overwriting the initial char c? And how to zero-terminate a string?

This example was given in K&R's first chapter and he never introduces strlen and strcpy in that so I thought there must be a way to do this without using them.

Of course there's a way to do it without fgets, strlen and strcpy (you could, for example, write them all yourself!).

But perhaps something like this:

Code:

i = len = 0;
while ((c = getchar()) != EOF) {
    if (c == '\n') {
        if (i > len) {
            len = i;
            // copy line to longest
        }
        i = 0;
    }
    else
        line[i++] = c;
}

When copying line to longest don't leave off the last character! And remember to zero-terminate it, i.e., set the char after the last one you copied to '\0'. Surely the book must mention that. If the book hasn't mentioned that yet, then you can't print it out using printf (since printf wouldn't know where to stop printing characters), but you could print it with a loop that only prints the first len chars.