fold line program : takes lines from the stdin until EOF (ctrl+D), and folds them on more rows, just like in word.

foldLine1.cpp

#include <stdio.h>
#define MAXLINE 400
#define FOLDLINE 40

int getline(char line[MAXLINE]){
    int i=0, c;
    while ((c=getchar()) != EOF && c!= '\n'){
        line[i++]=c;
    }
    if (c=='\n') line[i++]=c;
    line[i]='\0';
    
    return i;
}

int foldLine(char line[], int length){
    int index=0, j=0;
    
    if (length<=FOLDLINE+1) {
        printf("%s", line);
        return 0;
    }
    
    while (j<=length){
        
        //the next 40(e.g.) chars
        index=j+FOLDLINE;
        
        //if the chars left in line are less that 40(e.g.), print what's left, ret
        if(index>length) {
            while (j<=length){
                printf("%c",line[j]);
                j++;
            }
            return 0;
        }
        //printf("\nj=%d",j);
        //go back until you have reached the first white character
        while ((index > j ) && (line[index] != ' ') && (line[index] != '\t') ) {
            index--;
            //printf(" %d", index);
        }
        
        if(index<=j)
            for (int k=j; k<(j+FOLDLINE); k++) {
                printf("%c", line[k]);
            }
        else
        //print from the start to the last white character found front->back
        for (int k=j; k < index; k++){
            printf("%c",line[k]);
        }
        
        printf("\n");
        
        if (index<=j) index=index+FOLDLINE-1;
        j=index+1;
        
    }
    
}

int main(){
    int length=0;
    char line[MAXLINE];
    
    while ((length=getline(line)) > 0){
        
        foldLine(line, length);
    }

    
    return 0;
}