How to retrieve data and not entire lines in C?

Question

Hi,

Right now I use:

    char    record[BUFLEN];
    if(fgets(record, BUFLEN, fp) != NULL) {

      /* some code */

    }

to get lines from input like:

city=Boston;name=Bob;age=35
city=New York;name=Michael;age=29

Can I use something else in C that would give me not entire lines until '\n' but separate pairs like: "city=Boston" then "name=Bob", etc?

Answer 1

Check out the strtok() function. Successive calls will retrieve each token from the string.

Using your example:

char    record[BUFLEN];
if(fgets(record, BUFLEN, fp) != NULL) {
    char *token;

    token = strtok( record, ";" );
    while ( token != NULL )
    {
            doSomethingWith( token );
            token = strtok( NULL, ";" );
    }
}

Answer 2

you could read it a byte at a time using fgetc.

read up till = into one array then up till ; in another

        do {
          c = fgetc (pFile);

          if (c == ';') 
          // etc

        } while (c != EOF);

Answer 3

You could possibly duplicate the functionality of fgets(), only have it "fget" by a delimiter you specify, rather than \n. Code would look something like (THIS IS PSEUDOCODE):

In this function, "DELIM" is the delimiter you want to use. rather than \n, it might be ;.

char *GOEfgets(char *buf, int BUFLEN, FILE *fp, char DELIM)
{
   int i = 0; /* counter */
   int character;

   while(character = fgetc(fp)) /* we get a char from the stream one at a time */
   {
      buf[i] = (char)character; /* store that character in the stream */

      if ((char)character == DELIM) /* if we run into our delimiter, we stop */
      {
         return buf;
      }
   }

}

Answer 4

This looks like one of those relatively rare occasions when scanf() could be used.

You could try:

while (fscanf(fp, "%[^=]=%[^;]", name, value) == 2)
{
    if ((c = fgetc(fp)) == EOF)
        break;
    else if (c == ';')
        ...continue with same line...
    else if (c == '\n')
        ...wrap up current line...
    else
        ...congratulations - format error of some sort...
}

Alternatively, continue to use 'fgets()' but use 'sscanf()' in a loop similar to this.

Working demo code:

#include <stdio.h>
int main(void)
{
    char name[20];
    char value[20];

    while (fscanf(stdin, "%19[^=]=%19[^;]", name, value) == 2)
    {
        int c;
        if ((c = fgetc(stdin)) == EOF)
            break;
        else if (c == ';')
            printf("name = %s; value = %s\n", name, value);
        else if (c == '\n')
            printf("name = %s; value = %s\n", name, value);
        else
            fprintf(stderr, "Ooops!\n");
    }
    return(0);
}