count only lines of code...

Question: How can I only count the lines of code in a source file and ignore the comment lines and blank lines?
For example, if I have a source file as follows how would I only count the lines as described above.
Thanks!
Flight

Code:

#include <stdio.h>
#include <stdlib.h>

int main()
{

//declarations
char file_name[100], line1[10] ;
FILE *inp1, *out1 ;
int count, update_counter ;

   // init some stuf
   count=0 ;
   update_counter = 0 ;

    // prompt the user
    printf("Enter Filename : ")  ;

   // read the keyboard input
    fgets(file_name, sizeof(file_name), stdin);

   //remove the newline character from the end of the filename
   file_name[strlen(file_name) - 1] = '\0' ;

   // open input file
   inp1 = fopen(file_name, "r") ;

    if(inp1 == NULL)	
   {
      fprintf(stderr, "can't open %s\n", file_name) ;
      exit(EXIT_FAILURE) ;
   }

   // open output file #1
   out1 = fopen("output1.txt", "w") ;

    if(out1 == NULL)	
   {
       fprintf(stderr, "can't open %s\n", "output1.txt") ;
       exit(EXIT_FAILURE) ;
   }

    // count the words in the input file
    for ( ;; )
    {
       int ch = fgetc(inp1);
       if ( ch == EOF )
       {
          break;
       }
       if ( isalnum(ch) || ispunct(ch))
       {
          update_counter = 1;

       }
       else if ( isspace(ch) && update_counter )
       {
          count++ ;
          update_counter = 0;
       }
    }

    //for those files that end with lines with no line feeds
    //this will increment the counter one last time...
    if (update_counter)
    {
	  count++;
    }
 
    //write the word count to the output file
    fprintf(out1,"File %s contains %d words \n", file_name, count) ;

    // we're done...close files
    fclose(inp1) ;
    fclose(out1) ;

    return 0;
}

What part are you having trouble with?

Read a line, determine its type, and either count it or don't. Remember that:
- Comments and code can exist on the same line
- Comments can run across multiple lines

I would want to exclude those lines which are blank and those that are entirely a comment line. Just not sure how to do this.

Have you managed to open the file, and read a line in?

A line is empty if all it's characters meet the criteria for function isspace().
http://www.rt.com/man/isspace.3.html

Parse the line you've just read and check each character against that function. If they all return true, the line can be deemed empty.

To be a comment line (just comment, no code), the first non-white space characters need to be /* or //. Depending on which it is, the last non-white space character may need to be */. Again, some buffer parsing is needed for this. (watch out for the multi-line comments).

This is one small part in a much bigger design. Think about how you might fit it all together (on paper) before you start coding.

First you need to strip leading whitespace, that's easy so I won't go into it. Then do something like this:

Code:

if (string[0] == '/' && (string[1] == '*' || string[1] == '/'))
  /* Comment */
if (string[0] == '\0')
  /* Empty line */

Okay, I'll go into stripping leading whitespace:

Code:

void *lws(char *string) {
  char *s;

  for (s = string; *s != '\0' && isspace(*s); s++)
    ;
  memmove(string, s, strlen(s) + 1);
}

good advice. All comment lines are of the syntax "//". Would I be wise to choose the function 'getc' to search for a new line '\n' followed by the '/' and then another '/'? or is there a better way to accomplish this?

twm...you kind of blew me away with the stripping of the white space..my previous reply was to hammer's I didn't see yours until after I replied. Any advice on my previous reply...either twm or hammer.

>or is there a better way to accomplish this?
There's no "good" way to work with strings in C, but it's usually better to use fgets to get a line and then work with it in memory. My last post assumed such a setup.

Read a complete line with fgets() and parse the buffer in memory.

Depending on how you do this, you probably won't need to actually strip the leading white space, only advance the pointer to the beginning of the data. This saves the memmove() call in twm's sample.

flightsimdude, start by opening and reading the file. Write everything you read to the screen. Once you've done this, you have a basis to move forward on. Post it when you've done if you want comments/advice or if you have trouble. When this stage is complete, then start to worry about comment lines etc.

ok I'm completely humbled...not that I needed any! How do I advance the pointer...or is there another simpler way to read through the file and ignore the blank lines and lines that are comment only type lines? I know I'm probably trying your patience. If I am I won't post any more questions.
Thanks!
Flight

>This saves the memmove() call in twm's sample.
>How do I advance the pointer...
Well, if you want to do it the easy way...

Code:

char *sws(char *s) {
  while (isspace(*s))
    s++;

  return s;
}

>>I know I'm probably trying your patience.
Not at all.

Try doing as I said in my previous post. It's hard to help you if we don't know what level you're at, by seeing your code we can judge how to help you better.

thanks guys. It's late for me now. Ill be back tomorrow after I try what you have conveyed to me. Thanks again!