tcpl_ex-1-20.c

tcpl_ex-1-20.c

/*
 * Exercise 1-20. Write a program detab that replaces tabs in the input 
 * with the proper number of blanks to space to the next tab stop. Assume
 * a fixed set of tab stops, say every n columns. Should n be a variable 
 * or a symbolic parameter?  
 */

#include <stdio.h>

#define	MAXLEN	1000
#define	TABLEN	8
#define	TAB	'\t'
#define	NL	'\n'
#define  SPACE	' '

int getline(char line[], int limit);
void replacetab(char from[]);

int main(void)
{
	char line[MAXLEN];
	
	while (getline(line, MAXLEN) > 0)
	{
		replacetab(line);
	}

	return 0;

}

int getline(char line[], int limit)
{
	int i, j, c;
	for (i = j = 0; (c = getchar()) != EOF && c != NL; j++)
	{
		if (i < limit - 2)
		{
			line[i++] = c;
		}
	}
	if (c == NL)
	{
		line[i++] = NL;
		j++;
	}
	line[i] = '\0';
	
	return j;
}

void replacetab(char from[])
{
	int i, j, c, pos, offset;
	for (i = pos = 0; (c = from[i]) != '\0'; i++)
	{
		if (c == TAB)
		{
			offset = pos;
			for (j = 0; j < TABLEN - (offset % TABLEN); j++)
			{
				putchar(SPACE);
				pos++;
			}
		}
		else 
		{
			putchar(c);
			pos++;
		}
	}
}