tempWord[0]='\0' Does not reset String somehow - c

Question

I wrote a program in C, The expected result should be:
$ cat poem.txt
Said Hamlet to Ophelia,
I'll draw a sketch of thee,
What kind of pencil shall I use?
2B or not 2B?
$ ./censor Ophelia < poem.txt
Said Hamlet to CENSORED,
I'll draw a sketch of thee,
What kind of pencil shall I use?
2B or not 2B?
But I got this:
$ ./censor Ophelia < poem.txt
Said Hamlet tomlet CENSORED,
I'lllia drawlia arawlia sketcha ofetcha theecha,
Whatcha kindcha ofndcha pencila shallla Ihallla usellla?
2Bsellla orellla notllla 2Botllla?
I use tempWord to store every word and compare it with the word that needs to be censored. Then I use tempWord[0]='\0' to reset the temp String, so that I can do another comparison. But it seems not working. Can anyone help?
# include <stdio.h>
# include <string.h>
int compareWord(char *list1, char *list2);
int printWord(char *list);
int main(int argc, char *argv[]) {
int character = 0;
char tempWord[128];
int count = 0;
while (character != EOF) {
character = getchar();
if ((character <= 'z' && character >= 'a') ||
(character <= 'Z' && character >= 'A') ||
character == 39) {
tempWord[count] = character;
count++;
} else {
if (count != 0 && compareWord(tempWord, argv[1])) {
printf("CENSORED");
count = 0;
tempWord[0] = '\0';
}
if (count != 0 && !compareWord(tempWord, argv[1])) {
printWord(tempWord);
count = 0;
tempWord[0] = '\0';
}
if (count == 0) {
printf("%c", character);
}
}
}
return 0;
}
int printWord(char *list) {
// print function
}
int compareWord(char *list1, char *list2) {
// compareWord function
}

Answer 1

There are multiple issues in your code:
You do not test for end of file at the right spot: if getc() returns EOF, you should exit the loop immediately instead of processing EOF and exiting at the next iteration. The classic C idiom to do this is:
while ((character = getchar()) != EOF) {
...
For portability and readability, you should use isalpha() from <ctype.h> to check if the byte is a letter and avoid hardcoding the value of the value of the apostrophe as 39, use '\'' instead.
You have a potential buffer overflow when storing the bytes into the tempWord array. You should compare the offset with the buffer size.
You do not null terminate tempWord, hence the compareWord() function cannot determine the length of the first string. The behavior is undefined.
You do not check if a command line argument was provided.
The second test is redundant: you could just use an else clause.
You have undefined behavior when printing the contents of tempWord[] because of the lack of null termination. This explains the unexpected behavior, but you might have much worse consequences.
printWord just prints a C string, use fputs().
The compWord function is essentially the same as strcmp(a, b) == 0.
Here is a simplified and corrected version:
#include <ctype.h>
#include <stdio.h>
#include <string.h>
int main(int argc, char *argv[]) {
char tempWord[128];
size_t count = 0;
int c;
while ((c = getchar()) != EOF) {
if (isalpha(c) || c == '\'') {
if (count < sizeof(tempWord) - 1) {
tempWord[count++] = c;
}
} else {
tempWord[count] = '\0';
if (argc > 1 && strcmp(tempWord, argv[1]) == 0) {
printf("CENSORED");
} else {
fputs(tempWord, stdout);
}
count = 0;
putchar(c);
}
}
return 0;
}
EDIT: chux rightfully commented that the above code does not handle 2 special cases:
words that are too long are truncated in the output.
the last word is omitted if it falls exactly at the end of file.
I also realized the program does not handle the case of long words passed on the command line.
Here is a different approach without a buffer that fixes these shortcomings:
#include <ctype.h>
#include <stdio.h>
int main(int argc, char *argv[]) {
const char *word = (argc > 1) ? argv[1] : "";
int count = 0;
int c;
for (;;) {
c = getchar();
if (isalpha(c) || c == '\'') {
if (count >= 0 && (unsigned char)word[count] == c) {
count++;
} else {
if (count > 0) {
printf("%.*s", count, word);
}
count = -1;
putchar(c);
}
} else {
if (count > 0) {
if (word[count] == '\0') {
printf("CENSORED");
} else {
printf("%.*s", count, word);
}
}
if (c == EOF)
break;
count = 0;
putchar(c);
}
}
return 0;
}

Answer 2

tempWord[0] = '\0';
It will not reset the variable to null. It just assign the '\0' to the first position. But The values which are assigned are still in memory only. Only the first position is assigned to '\0'. So, to reset the character array try the below.
memset(tempWord, 0, 128);
Add the above line instead of your tempWord[0] = '\0'.
And also this will solves you don't need to add the '\0' at end of each word. This itself will work. But for the first time your have to reset the character array using the same memset function. Before entering to the loop you have to set the tempWord to null using the memset function.

Answer 3

Using tempWord[0]='\0' will not reset the whole array, just the first element. Looking at your code, there are 2 ways you could go forward, either reset the whole array by using memset:
memset(tempWord, 0, sizeof tempWord);
or
memset(tempWord, 0, 128);
(or you can only clear it by the size of last word, also it needs string.h which you have already included),
Or you could just set the element after the length of 'current word' to be '\0' (ex, if current word is the then set tempWord[3]='\0', since strlen checks the string till null char only) which can be placed before those 2 ifs checking if the strings are equal or not, your new while loop will look like this:
{
character = getchar();
if((character<='z' && character>='a')||(character<='Z' && character>='A')||character == 39)
{
tempWord[count]=character;
count++;
}else {
tempWord[count]='\0';
if(count!=0 && compareWord(tempWord, argv[1]))
{
printf("CENSORED");
count=0;
}
if(count!=0 && !compareWord(tempWord, argv[1]))
{
printWord(tempWord);
count=0;
}
if (count==0)
{
printf("%c", character);
}
}
}
(it works, tested)