Writing selected text from a file to txt file using C - c

Question

prefacing by saying, I've lurked in Stackoverflow and this is my first Question, but thank you all you kind souls for your contributions!
I am trying to write comments and classes from a .java file to a .txt file using C programming. I used the fgetc and fputc functions to do this and managed to write the whole file across, but when I try to communicate that I only want the comments right up to the class (so before the "{" and everything after the "}") it seems to not print anything. I am quite new to C and just a bit stuck. I have included my code below, any help would be super appreciated. Sorry if this is hard to understand, I am not natively English speaking.
#include <stdio.h>
#include <stdlib.h>
int main(int argc, char **argv)
{
FILE *input = fopen("text.java", "r"); //opens file
FILE *comments = fopen("comments.txt", "w");
char ch;
ch = fgetc(input);
while(ch != EOF)
{
while(!strcmp(ch, "{"))
{
fputc(ch, comments);
ch = fgetc(input);
}
ch = fgetc(input);
}
fclose(input);
fclose(comments);
return 0;
}

Answer 1

As already pointed out in the comments section by someone else, your code has the following errors:
The return type of fgetc is int, not char. The value EOF cannot be represented in char, so you should not truncate the int return value to char. Instead, you should declare ch as an int.
The function strcmp is for comparing strings, not characters.
When calling fgetc in your inner loop, you are not checking the return value for EOF.
Also, your algorithm for solving the problem does not seem correct.
One way to solve the problem is for your program to always remember whether it is inside a brace or not, and to act accordingly. For example, you can declare a bool inside_brace variable which always specifies whether you are inside a brace or not, like this:
#include <stdio.h>
#include <stdlib.h>
//the following line is necessary for the "bool" data type
#include <stdbool.h>
int main( int argc, char **argv )
{
FILE *input = fopen("text.java", "r");
FILE *comments = fopen("comments.txt", "w");
int ch;
bool inside_brace = false;
while ( ( ch = fgetc(input) ) != EOF )
{
if ( !inside_brace )
{
if ( ch == '{' )
{
inside_brace = true;
continue;
}
fputc( ch, comments );
}
else //inside a brace
{
if ( ch == '}' )
{
inside_brace = false;
continue;
}
}
}
fclose(input);
fclose(comments);
return EXIT_SUCCESS;
}
Note that this solution will only work if you only have one nesting level of braces, i.e. that you don't have one { inside another { without first closing the first { with a }. If it is possible that you have more than one level of nesting, then the variable bool inside_brace will not be sufficient. Instead, you will need a counter to keep track of the current nesting level, for example like this:
#include <stdio.h>
#include <stdlib.h>
int main( int argc, char **argv )
{
FILE *input = fopen("text.java", "r");
FILE *comments = fopen("comments.txt", "w");
int ch;
int nesting_level = 0;
while ( ( ch = fgetc(input) ) != EOF )
{
switch ( ch )
{
case '{':
nesting_level++;
continue;
case '}':
nesting_level--;
if ( nesting_level < 0 )
{
fprintf( stderr, "Error: Negative nesting level encountered!\n" );
return EXIT_FAILURE;
}
continue;
}
if ( nesting_level == 0 )
fputc( ch, comments );
}
}
fclose(input);
fclose(comments);
return EXIT_SUCCESS;
}