Sample demo to parse CSV text

/*
StudentRec.c a simple student record demo.

This program:

1- Prints the current working directory.
2- Asks user to specify the file name containing the records of students.
3- Reads the record from the file.
4- Prints each record with statistics

Each line in the file is a none-empty comma-separated values containing a
student name and three float numbers in the range [0.00, 100.0] indicating the
result of three exams for each students. Example:

John Smith,71,68,92
Paul Hunter,69,73,82
Mary McDana,81,83,90

There are variuos constants in the program which could be altered to change the
limits of the program. For example, MAX_STUDENT_RECS indicates the maximum number
of strudent records which is defined to be 20. You may alter it to any desirable
value from 1 to any positive valid int value.

Tested with Visual Studio .Net 2008 Standard C, Quincy 2005 and Dev C/C++ 4.9

*/

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

/*
The size of buffers to hold directory path.
(The maximum number of characters allowed for a directory (folder) path
*/
#define  MAX_PATH_LENGTH    2048

/*
The maximum length of file name.
*/
#define  MAX_FILENAME_LENGTH    256

/*
The maximum length of each record line.
*/
#define  MAX_LINE_LENGTH    256

/*
The maximum number of student records.
*/
#define  MAX_STUDENT_RECS   20

/*
A constant used as null character. The char representation, ' \ 0 '
has an issue when published in a blog, causeing the code to produce
compile error.
*/
const char NULL_CHAR = (char) 0;

/*
A struct record definition. Each student record will be saved in one
variable of student_rec type. (Actually an array of this).
*/
struct student_rec
{
    /* The name of student */
   char   name [MAX_LINE_LENGTH];
   float  exam1;    /* the result of exam1 */
   float  exam2;    /* the result of exam2 */
   float  exam3;    /* the result of exam3 */
};

/*
The array holding all the student records.
*/
struct student_rec records [MAX_STUDENT_RECS];

/*
The main program. We have not used the command-line arguments in this demo.
*/
int main(int argc, char *argv[])
{
    /* A buffer to hold the current working directory. */
   char buffer [MAX_PATH_LENGTH];

   /* The string to hold the filename of record file. */
   char filename [MAX_FILENAME_LENGTH];

   /* The String to hold each record line in loop. */
   char line [MAX_LINE_LENGTH];

   /* A string to hold the caption for record statistics. */
   char stat [MAX_FILENAME_LENGTH];

   /* used to trim the new-line characters off the line. */
   int len;

   /* The file interface to work with record file. */
   FILE* fp;

   /* a pointer to tokenize each record field. */
   char *pTok;

   /* The primary delimiter list to tokenize the fields of each record. */
   const char *delim = ",";

   /* The alternative delimiter list to tokenize the fields of each record. */
   /* (used for last token/field). */
   const char *delimLast = "\r\n";

   /* variables to hold the sums of each exams results. */
   float exam1, exam2, exam3;

   /* count : the total number of student records. */
   /* n : misc for loop variable. */
   int count, n;


   /* gets the current working directory, and prints it. */
  _getcwd(buffer, MAX_PATH_LENGTH);
  printf ("Current Working Directory: %s\n", buffer);

  /* reads the file name from keyboard. */
  printf ("Enter File name: ");
  fgets(filename, MAX_FILENAME_LENGTH - 1, stdin);

    /* trims the appnded new-line at the end. */
  len = strlen (filename);
  if (filename [len - 1] == '\n')
     filename [len - 1] = NULL_CHAR;

  /* echo back the read file name. */
  printf ("Filename: %s\n", filename);

  /* opens the record file: */
  if ((fp = fopen (filename, "r")) == NULL)
  {
      /* prints the error in std error device if failed. */
     fprintf (stderr, "*** Cannot open file %s for input.\n", filename);
     system ("PAUSE");
     return 1;  /* exits with error status 1 */
  }

  /* reads all the records up to a maximum number. */
  for (count = 0; count < MAX_STUDENT_RECS; )
  {
      /* reads the next line; if no more lines, breaks. */
     if (fgets (line, MAX_LINE_LENGTH - 1, fp) == NULL)
        break;

     /* obtins the first token/field (name) */
     pTok = strtok (line, delim);

     /* If no token, continues (reading next line) */
     if (pTok == NULL || *pTok == NULL_CHAR || *pTok == '\n')
        continue;

     /* if a record, copies the first field/token into name field of the
        next student record */
     /* element in array. */
     strcpy (records [count].name, pTok);

     /* obtain the next token/field (exam1) */
     pTok = strtok(NULL, delim);

     /* It shouldn't be a null or empty record. */
     if (pTok == NULL || *pTok == NULL_CHAR || *pTok == '\n')
     {
         /* If it is, skips this line with a warning. */
        fprintf (stderr, "*** Warning! Skipping invalid record; name : %s\n",
            records [count].name);
        continue;
     }

     /* converts exam1 to a float number and save it in record element. */
     records [count].exam1 = atof (pTok);

     /* obtain the next token/field (exam2) */
     pTok = strtok(NULL, delim);

     /* It shouldn't be a null or empty record. */
     if (pTok == NULL || *pTok == NULL_CHAR || *pTok == '\n')
     {
         /* If it is, skips this line with a warning. */
        fprintf (stderr, "*** Warning! Skipping invalid record; name : %s\n",
            records [count].name);
        continue;
     }

     /* converts exam2 to a float number and save it in record element. */
     records [count].exam2 = atof (pTok);

     /* obtain the final token/field (exam3) */
     pTok = strtok(NULL, delimLast);

     /* It shouldn't be a null or empty record. */
     if (pTok == NULL || *pTok == NULL_CHAR || *pTok == '\n')
     {
         /* If it is, skips this line with a warning. */
        fprintf (stderr, "*** Warning! Skipping invalid record; name : %s\n",
            records [count].name);
        continue;
     }

     /* converts exam3 to a float number and save it in record element. */
     records [count].exam3 = atof (pTok);

     /* because all lines may not be a valid record,
     we increment count here, not in for loop. */
     count++;
  }

  /* Now, displaying the records, and accumulating the results exam by
  exam for all students: */

  /* Initially, all 0. */
  exam1 = exam2 = exam3 = 0.0f;

    /* Displaying all records */
  for (n = 0; n < count; n++)
  {
      printf ("%30s\t%6.2f\t%6.2f\t%6.2f\t%6.2f\n", records [n].name,
          records [n].exam1, records [n].exam2, records [n].exam3,
             (records [n].exam1 + records [n].exam2 + records [n].exam3) / 3.0f);

      /* summing up results. */
      exam1 += records [n].exam1;
      exam2 += records [n].exam2;
      exam3 += records [n].exam3;
  }

  /* prints the stat. */
  sprintf(stat, "%d records, Average:", count);
  printf ("%30s\t%6.2f\t%6.2f\t%6.2f\n", stat, exam1 / (float) count,
      exam2 / (float) count, exam3 / (float) count);

   system ("PAUSE");
   return 0; /* exist with status OK. */
}