Ex 1-21

Write a program entab that replaces strings of blanks with the minimum number of tabs and blanks to achieve the same spacing. Use the same stops as for detab . When either a tab or a single blank would suffice to reach a tab stop, which should be given preference?

#include<stdio.h>
#define TABINC 8
#define MAXLINE 1000

void entab(char line[]);
int Getline(char s[], int lim);

main()
{
        char line[MAXLINE];
        int len;

        while((len = Getline(line, MAXLINE)) > 0){
                entab(line);
        }
}

int Getline(char s[], int lim)
{
        int i, c;

        for(i = 0; ((c = getchar()) != EOF) && c != ‘\n’; ++i)
                s[i] = c;
        if(c == ‘\n’){
                s[i] = ‘\n’;
                ++i;
        }

        s[i] = ‘\0’;

        return i;

}

void entab(char s[])
{
        int i, nt, nb;
        nt = nb = 0;

        for(i = 0; s[i] != ‘\n’; ++i){
                if(s[i] == ’ ‘){
                        if((i + 1) % TABINC != 0) {//Not enough blanks for a tab
                                ++nb;
                        } else {
                                nb = 0;
                                ++nt;  //Now has TABINC blanks to replace with a tab
                        }
                } else {
                        for(; nt > 0; —nt)
                                putchar(‘\t’);
                        if(s[i] == ‘\t’){
                                nb = 0;
                                putchar(‘\t’);
                        }
                        else
                                for(; nb > 0; —nb)
                                        putchar(’ ‘);
                        printf(“%c”, s[i]);
                }
        }
        putchar(‘\n’);
}