Parsing CSV file into Structs and Sort Alphabetically using C

Question

I am a bit lost after hours of googling and research. I need to put a CSV containing artist, title, albumName, duration, yearRealeased, and hotttness. I then need to sort the array of structs by title alphabetically.

So far I am just able to get the title but then I get an error while running the compiled code (it prints out 100 or so of the 10000 titles) : "Segmentation fault (core dumped) makefile:5: recipe for target 'test' failed" make: *** [test] Error 139

The layout of the CSV file is: SongNumber, SongID, AlbumID, AlbumName, ArtistID, ArtistLatitude, ArtistLocation, ArtistLongitude, ArtistName, Danceability, Duration, KeySignature, KeySignatureConfidence, Tempo, Hotttnesss, TimeSignature, TimeSignatureConfidence, Title, Year

I do not know how to ignore the values I am not trying to read from the file. As I only need to get the artist, title, albumName, duration, yearRealeased, and hotttness.

Any help would be very appreciated as I am at a complete loss of what to do at this point. Thank You in advance.

I am also getting an error when compiling:

gcc -Wall -Wpedantic -std=c99 *.c -g -o 3240Assignment0
a0.c: In function ‘main’:
a0.c:52:34: warning: implicit declaration of function ‘strsep’ [-Wimplicit-function-declaration]
                  while ((Token = strsep(&line,","))) {
                                  ^
a0.c:52:32: warning: assignment makes pointer from integer without a cast [-Wint-conversion]
                  while ((Token = strsep(&line,","))) {
                                ^

Answer 1

This is terrible:

 newSong.title = malloc(sizeof(Token));
 strcpy(newSong.title,Token);           // strcpy()

As Token is declared to be a char *, sizeof(Token) is sizeof(char *) (probably 4...). So your are likely to write past end of allocated data which invokes Undefined Behaviour.

What you need is:

newSong.title = strdup(Token);

if strict C11 compatibility is not required, or if it is:

 newSong.title = malloc(1 + strlen(Token));
 strcpy(newSong.title,Token);           // strcpy()

BTW, it you want C11 strict compatibility, you will need to use strtok instead of strsep, or revert to by hand separator search with strchr

Once this is fixed, try to process other fields the same you currently process title.

But beware, as you failed to give an example of file, I could not test and other problems could remain...

Answer 2

There are many issues and your program is overly complicated.

Here is the corrected and simplified version.

• consistent indentation
• No more typedef song *songPtr; which only adds confusion (read this for more details)
• correct usage of strtok
• replaced non standard strsep by the similar strtok (google "strtok vs strsep")
• correct allocation of memory for songs
• correct allocation of strings in songs (title, artist)
• no more useless dynamic allocation of buffer which has a fixed size anyway
• declaration of variables where they are used (this requires a non totally outdated C compiler)
• avoiding useless (and in your case even wrong) copying around of data
• etc.

There is still room for more improvement, for example there is no error checking for memory allocation.

---

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

#define BUFFSIZE 512
#define _BSD_SOURCE 
typedef struct song {
  char *artist;
  char *title;
  char *albumName;
  float duration;
  int yearRealeased;
  double hotttness;
} song;


int main() {
  FILE *songStream;
  int count = 0;
  int size = 100;

  song** allSongsArray = malloc(size * sizeof(song*));

  songStream = fopen("data.txt", "r");

  if (songStream == NULL) {
    printf("Unable to open file");
    exit(1);

  }
  else {
    printf("Opened File\n");

    char buffer[BUFFSIZE + 1];
    while (fgets(buffer, BUFFSIZE, songStream) != NULL) {

      song *newSong = malloc(sizeof(song));

        char *line = buffer;
      int index = 0;
      char *Token;

      while ((Token = strtok(line, ","))) {
        line = NULL;   // line needs to be set to NULL here, read 
                       // the strtok/strsep documentation for details

        switch (index)
        {
        case 17:
          newSong->title = malloc(strlen(Token) + 1);
          strcpy(newSong->title, Token);
          break;
        case 8:
          newSong->artist = malloc(strlen(Token) + 1);
          strcpy(newSong->artist, Token);
          break;

          // add the cases for the other columns here
        }

        index++;
      }

      allSongsArray[count++] = newSong;     // store pointer to new song in array

      if (count == size) {
        size = size + 100;
        allSongsArray = realloc(allSongsArray, size * sizeof(song*));
      }
    }

    fclose(songStream);
  }

  // display all songs read (count is the number of songs)
  for (int i = 0; i < count; i++)
  {
    fprintf(stdout, "%s, %s\n", allSongsArray[i]->title, allSongsArray[i]->artist);
  }

  return 0;
}

If strdup is available you can replace this:

newSong->artist = malloc(strlen(Token) + 1);
strcpy(newSong->artist, Token);

by:

newSong->artist = strdup(Token);

Or you can write your own strdup function (2 line sof code).