Can't figure out why I am getting strange output - c

Question

I'm pretty novice. I've been working through the K&R C programming book, and one of the exercises was to write a program that prints any input lines that are longer than 80. Here's my code:
include <stdio.h>
#define MAXLINE 1000
int getaline(char line[], int maxline);
int main()
{
int i, c;
char line[MAXLINE];
if ((c = getaline(line, MAXLINE)) > 80){
for (i =0; i < MAXLINE; ++i)
if (c != '\0')
printf("%c", line[i]);
printf("\n");
}
}
/* reads a line into S, returns the length of that line */
int getaline(char s[], int lim)
{
int c, i;
for (i = 0; i < lim-1 && (c = getchar()) != EOF && c != '\n'; ++i)
s[i] = c;
if (c == '\n') {
s[i] = c;
++i;
}
s[i] = '\0';
return i;
}
So I'll pipe a line longer than 80 chars to the compiled program. Here's the output:
cat input.txt | ./a.out
1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111
??i?F???4?w??>&Y?_???xf?7U?h#?
??i??7U?v??i??7U??7U?(?7U?#?
H??i?8?7U??7U?
It prints the line, but it gives all this anomalous output. I tried to figure out why, but I just can't seem to find why.
However, I am pretty sure that the problem lies in the getaline function.
Any help would be greatly appreciated! :)

Answer 1

You are confusing c with the current character.
Try this, change this
for (i =0; i < MAXLINE; ++i)
with
for (i = 0 ; i < c ; ++i)
and the check should be
if (line[i] != '\0')
instead of
if (c != '\0')
your getaline() function returns, i the position of the last character read, you are comparing it with the null termination byte.
Also if you are null terminating the string, why don't you just
printf("%s\n", line);
this code should work
#include <stdio.h>
#define MAXLINE 1000
int getaline(char line[], int maxline);
int main()
{
int i, c;
char line[MAXLINE];
if ((c = getaline(line, MAXLINE)) > 80)
printf("%s\n", line);
return 0; // you must return from main()
}
/* reads a line into S, returns the length of that line */
int getaline(char s[], int lim)
{
int c, i;
for (i = 0 ; (i < lim - 1) && ((c = getchar()) != EOF) && (c != '\n') ; ++i)
s[i] = c;
if (c == '\n')
{
s[i] = c;
++i;
}
s[i] = '\0';
return i;
}

Answer 2

You're checking c as though it were a character, when it's the line-length count; it will never be equal to \0, so you keep pringting.
if ((c = getaline(line, MAXLINE)) > 80){
// c now equals, let's say, 81
for (i =0; i < MAXLINE; ++i)
// c is still 81, we never fail
if (c != '\0')
printf("%c", line[i]);
printf("\n");
}
Consider this instead:
if (getaline(line, MAXLINE) > 80) {
for (i =0; i < MAXLINE; ++i)
{
c = line[i];
if (c != '\0')
printf("%c", c;
else
break;
}
printf("\n");
}

Answer 3

Replace
for (i =0; i < MAXLINE; ++i)
if (c != '\0')
printf("%c", line[i]);
by
for (i =0; i < c; ++i)
printf("%c", line[i]);