exercise1-18.md

Exercise 1-18

Write a program to remove trailing blanks and tabs from each line of input, and to delete entirely blank lines

Process

Decisions about how to interpret this exercise and the constraints around the solution

• 'trailing' meaning blanks: ' ' and tabs: '\t' AFTER the last char in the line and BEFORE the end of the line
• 'blank lines' meaning lines consisting of only blanks and tabs and '\n' or lines consisting of only a '\n'
• the solution won't deal with lines longer than the buffer, which in this case is 80
• if the last line in the input does not end in a '\n', the program will also not end in a '\n'

I decided to use the getline function from previous exercises as it seems fitting and a good way to structure the program.

There was some difficulty in cleaning up the order of operations so it reads logically.

I think a solution to handling infinitly long input lines would take a more complex approach similar to the previous exercise. After looking at some solutions online, the idea of the program doing multiple passes instead of trying to do it all in 1 chunk seems like a cool idea.

Final Code

#include <stdio.h>

#define MAX_LENGTH 80
#define FALSE	0
#define TRUE	1

int getline(char line[], int limit);

int main()
{
	char line[MAX_LENGTH];
	int len, i, endnewline = TRUE;
	
	while((len = getline(line, MAX_LENGTH)) != 0){
		
		/* does last input line end in newline */
		if(line[len - 1] == '\n')
			len = len - 1; /* skip newline char */
		else
			endnewline = FALSE;
		
		/* skip all trailing whitespace */
		while((line[len-1] == '\t' || line[len-1] == ' ') && (len > 0))
			len--;
		
		/* print output */
		if (len > 0) {
			for (i=0; i < len; i++)
				putchar(line[i]);
			
			if (endnewline == TRUE)
				putchar('\n');
		}
	}
	
	return 0;
}

/* getline: read a line into s, return length */
int getline(char line[], int limit)
{
    int c, i;
    
    for (i=0; i<limit-1 && (c=getchar()) != EOF && c!='\n'; ++i)
        line[i] = c;
    if (c == '\n') {
        line[i] = c;
        ++i;
    }
    line[i] = '\0';
    return i;
}

Output

Back to Main