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C-program to identify the comment in the code and print the comment.

Rajnish Tripathi 21:54

 Here in this article we will learn how to identify the comment in the c program and print that comment . In this code we will use the file handling . By using the file handling first we take input by the user and write it in this file and then read the code from the file and find the comment in the code.

Note:- the line start from // is a single line comment in C-programming and the content written in /*   comment */ is a multiline comment in C-programming.

So we have to find the both the comments in the code . 

To know more about file handling :-- Click here

Code:-

#include<stdio.h>
#include<string.h>

int main()
{
FILE *fp;
char str[200];
// logic for writing the code in the file
fp=fopen("file.txt","w");
if(fp==NULL)
printf("Error in opening the file\n");
else
{
char ch;
printf("Enter the $ for ending the editing\n");
scanf("%c",&ch);
fputc(ch,fp);
while(ch!='$')
{
scanf("%c",&ch);
fputc(ch,fp);
}
fclose(fp);
}
printf("The comments are:-\n");
// logic for finding the comment in the code
fp=fopen("file.txt","r");
if(fp==NULL)
printf("Error in opening the file\n");
else
{
while(fgets(str,200,fp)!=NULL)
{
int i,l,flag=0;
l= strlen(str);
for(i=0;i<l-1;i++)
{
// logic to find single line comment
if(str[i]=='/' && str[i+1]=='/')
{
for(int j=i+2;j<l;j++)
printf("%c",str[j]);
printf("\n");
break;
}
// logic to find comment is multiline
if(str[i]=='/' && str[i+1]=='*')
{
i=i+2;
for(int j=i;str[j];j++)
{
// if there is any single line comment inside the multiline
if(str[j]=='/' && str[j+1]=='/')
{
j+=2;
for(int k=j;k<l;k++)
printf("%c",str[k]);
break;
}
else
printf("%c",str[j]);
}
printf("\n");
flag=1;
break;
}
}
// if multiline comment found
// then scan next line for the full comment
if(flag==1)
{
while(fgets(str,200,fp)!=NULL)
{
int i=0;
l=strlen(str);
while(i<l-1)
{
// if there is any single line comment
if(str[i]=='/' && str[i+1]=='/')
{
i+=2;
for(int k=i;k<l;k++)
printf("%c",str[k]);
break;
}
else
{
if(str[i]=='*' && str[i+1]=='/')
{
flag=0;
break;
}
printf("%c",str[i]);
i++;
}
}
printf("\n");
// if comment end then break
if(flag==0)
break;
}
}
}
}
return 0;
}

Output:- 

 Lets a input of code:-
#include<stdio.h>
int main()
{
/* this is multiline comment
// and this is single line comment inside the multiline comment
and this is end of the multiline comment*/
}
// End of the main function
$

 when we give the this input then first this code will written in the file . and then we will read the file and find the comment inside C-program.
Enter the $ for ending the editing
#include<stdio.h>
int main()
{
/* this is multiline comment
// and this is single line comment inside the multiline comment
and this is end of the multiline comment*/
}
// End of the main function
$

The comments are:-
this is multiline comment

and this is single line comment inside the multiline comment

and this is end of the multiline comment
End of the main function



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