reading in lines of text from file

Question

gcc 4.5.1 c89

I am using the following code to read in a line of text from a configuration file. The configuration file is small at the moment, will grow with new fields to add. And I can pretty much design what the configuration file will look like myself. So I have done it in the following way:

config.cfg

# Configuration file to be loaded 

# protocol to use either ISDN, SIP, 
protocol: ISDN

# run application in the following mode, makecall or waitcall
mode: makecall

I have used the colon as a way to search for the type of configuration that will be needed. I am just wondering if there a better way to do this?

My code I have used is as follows:

static int load_config(FILE *fp)
{
    char line_read[LINE_SIZE] = {0};
    char *type = NULL;
    char field[LINE_SIZE] = {0};
    char *carriage_return = NULL;

    /* Read each line */
    while(fgets(line_read, LINE_SIZE, fp) != NULL) {
        if(line_read != NULL) {
            /* Ignore any hashs and blank lines */
            if((line_read[0] != '#') && (strlen(line_read) > 1)) {
                /* I don't like the carriage return, so remove it. */
                carriage_return = strrchr(line_read, '\n');
                if(carriage_return != NULL) {
                    /* carriage return found so relace with a null */
                    *carriage_return = '\0';
                }

                /* Parse line_read to extract the field name i.e. protocol, mode, etc */
                parse_string(field, line_read);
                if(field != NULL) {
                    type = strchr(line_read, ':');
                    type+=2; /* Point to the first character after the space */

                    if(strcmp("protocol", field) == 0) {
                        /* Check the protocol type */
                        printf("protocol [ %s ]\n", type);
                    }
                    else if (strcmp("mode", field) == 0) {
                        /* Check the mode type */
                        printf("mode [ %s ]\n", type);
                    }
                }
            }
        }
    }

    return TRUE;
}

/* Extract the field name for the read in line from the configuration file. */
static void parse_string(char *dest, const char *string)
{
    /* Copy string up to the colon to determine configuration type */
    while(*string != ':') {
        *dest++ = *string++;
    }
    /* Insert nul terminator */
    *dest = '\0';
}

Answer 1

easier should be:

static int load_config(FILE *fp)
{
  int r=0;
  char line[LINE_SIZE], field[LINE_SIZE], type[LINE_SIZE], dummy[LINE_SIZE];

  /* Read each line */
  while( fgets(line, LINE_SIZE, fp) )
  {
    if( strchr(line,'\n') ) *strchr(line,'\n')=0;
    if( 3==sscanf(line,"%[^: ]%[: ]%s,field,dummy,type) )
      ++r,printf("\n %s [ %s ]",field,type);
  }
  return r;
}

Answer 2

<regex.h> is your friend!

http://www.gnu.org/s/libc/manual/html_node/Regular-Expressions.html

Answer 3

If you can design what the configuration file will look like i'd go for XML, parsing it with Expat. It's painless.

Answer 4

The standard answer to simple parsing problem is to use lex and yacc.

However, as you have freedom to set the form of the configuration file, you should use one of the numerous libraries that implement various configuration file formats, and just use that one.

http://www.google.com/search?q=configuration+file+parser

http://www.nongnu.org/confuse/ for instance, would seem to cover your needs adequately, but take a look at various other options that might be simpler as well.