Question

The legal department of a big company is looking for a way to redact certain sensitive documents before they can be released publicly. A redacted document has certain words deleted or blacked out.

For this problem, censored words will be hidden with asterisks, leaving only their first letter intact. Censored words should be matched regardless of their case.

Write program redact.c that reads entire lines from the user, and hides certain words according to a list of words received as program arguments, as illustrated in the following example.

$ cat udhr_art26.txt
(1) Everyone has the right to education. Education shall be
free, at least in the elementary and fundamental stages.
Elementary education shall be compulsory.  Technical and
professional education shall be made generally available and
higher education shall be equally accessible to all on the
basis of merit.
(2) Education shall be directed to the full development of
the human personality and to the strengthening of respect
for human rights and fundamental freedoms.  It shall promote
understanding, tolerance and friendship among all nations,
racial or religious groups, and shall further the activities
of the United Nations for the maintenance of peace.
(3) Parents have a prior right to choose the kind of
education that shall be given to their children.
$ ./redact education right t < udhr_art26.txt
(1) Everyone has the r**** to e********. E******** shall be
free, at least in the elementary and fundamental stages.
Elementary e******** shall be compulsory.  Technical and
professional e******** shall be made generally available and
higher e******** shall be equally accessible to all on the
basis of merit.
(2) E******** shall be directed to the full development of
the human personality and to the strengthening of respect
for human r****s and fundamental freedoms.  It shall promote
understanding, tolerance and friendship among all nations,
racial or religious groups, and shall further the activities
of the United Nations for the maintenance of peace.
(3) Parents have a prior r**** to choose the kind of
e******** that shall be given to their children.
$

Here are a list of requirements, assumptions and hints:

This program shall contain no global variables.

We assume that the maximum number of characters a line can contain is 80.

Censored words less than 2 characters should be ignored.

You will probably need to split the problem into a hierarchy of functions. A possible set of functions could include:

A function that hides a certain number of characters in a line, starting from a given position.

A function that hides a certain word in a line (e.g. by iterating through the string and locating the word).

A function that hides a collection of words in a line.

The main function should be the brain, reading the line from the user and calling the censor function before displaying the censored line.

In order to match strings while ignoring their case, you can use strncasecmp()function provided by the libc.

List of some important libc functions that are used in the reference program: strlen(), strncasecmp(), fgets().

follot the guidelines if possible

Answer 1

Please read the comments to understand the functionality of the code.

#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <ctype.h>
//
///*
// *
// */
//function to split the sentence read from file into words
int split(char *str, char *arr[20]) {
    int beginIndex = 0;
    int endIndex;
    int maxWords = 20;//Assuming Maximum words in a line can be 20
    int wordCnt = 0;

    while (1) {
        while (isspace(str[beginIndex])) {//check if the character is a space
            ++beginIndex;
        }
        if (str[beginIndex] == '\0')//if it is a space then this is end of word, add null character
            break;
        endIndex = beginIndex;
        while (str[endIndex] && !isspace(str[endIndex])) {//find the starting and eding index of the word
            ++endIndex;
        }
        int len = endIndex - beginIndex;
        char *tmp = calloc(len + 1, sizeof (char));
        memcpy(tmp, &str[beginIndex], len);//get the word
        arr[wordCnt++] = tmp;//store the word in array
        beginIndex = endIndex;
        if (wordCnt == maxWords)
            break;
    }
    return wordCnt;
}

void censorLine(char *line, int count, char **words) {
    int i, j, k;
    char *arr[20]; //Maybe 20 words in a line
    int n = split(line, arr);
    for (i = 0; i < n; i++) {
        for (j = 0; j < count; j++) {
            if (strncasecmp(arr[i], words[j], strlen(words[j])) == 0)
                for (k = 1; k < strlen(arr[i]); k++)
                    arr[i][k] = '*'; //replace characters with * except the first character
        }
        printf("%s ", arr[i]);
    }
}
int main(int argc, char** argv) {
    FILE *fin;
    fin = fopen("udhr_art26.txt", "r");
    int i;
    for (i = 0; i < argc; i++) {
        printf("%s\n", argv[i]);
    }
    char* line = malloc(80); //read 1 line and allocate 80 because 1 line can have 80 characters
    while (fgets(line, 80, fin) != NULL) {//read data from file line by line
        censorLine(line, argc, argv); //censor line to the user
    }
}