Reading in File Help

Hi, I'm trying to read from a file and I'm getting a segmentation fault, can someone help me with what I'm doing wrong:

My .txt file looks exactly like this:

Code:

---

-CD-
Artist: Outkast
Title: Stankonia
Year: 1997

-CD-
Artist: Jay Z
Title: Reasonable Doubt
Year: 1993

-CD-
Artist: Atmosphere
Title: Overcast
Year: 1995

---

Those years might not be right but whatever, its a test :)

Now this is my code:

Code:

---

#include <iostream.h>
#include <fstream.h>


int main()
{
  ifstream infile;
  char* line = new char[512];
  char* temp = new char[100];
  char* garbage = new char[50];
  char* artist = new char[50];
  char* title = new char[50];
  char* year = new char[50];

  infile.open("databaseFile.txt");

  while ( infile.peek() != EOF )
    {

      infile.getline(garbage,100);

      infile.getline(line,512);

      temp = strtok(line, " ");
      strcpy(garbage,temp);

      temp = strtok(NULL, "\n");
      strcpy(artist, temp);

      temp = strtok(NULL, " ");
      strcpy(garbage,temp);

      temp = strtok(NULL, "\n");
      strcpy(title,temp);

      temp = strtok(NULL, " ");
      strcpy(garbage,temp);

      temp = strtok(NULL, "\n");
      strcpy(year,temp);

      infile.getline(garbage,100);

    }

}

---

The first part should ignore the first line because that just says "-CD-". Then I tried to strtok with the delimeter of " " and ignore that part because thats the part that says "Artist:", "Title: ", and "Year: ". Then I try to strtok with "\n" and save that as the actual artist, title, and year. I strtok'ed with "\n" because artists and titles could have a space in their name so if I strtok with the " " it will break it up. But I'm getting a segmentation fault and I put some cout's in there to find out how far it got and it dumps the core right after it strtok's the artist.

Can someone please Help!

you're not checking the return value of strtok - you're probably passing a NULL pointer to strcpy.

Boy you sure like overcomplicating things. For starters, why aren't you just using arrays? I mean, it's not like you're resizing anything anyway. Next, you can do all of this with one single buffer. This is what you should be doing:

Code:

---

while not at the end of the file
    read a line
    if line == only whitespace
        continue
    if line == CD
        begin a new record
    if line == artist
        stick artist info into record
    if line == title
        ...
    if line == year
        ...

---

It can even be simpler than that if you're sure they'll always have the same format. If you want it to be safe, you do the above with a few variables to track what you've already got in the record.

You then decide what you do with info that isn't right:

Quote:

---

-CD-
Artist: Jay Z
Title: Reasonable Doubt
Title: Reasonable Foo
Year: 1993

---

Now here we have two title lines. One of these shouldn't be there. You have to account for something like this.

At any rate, you're overcomplicating this. You don't need strtok at all. You should however use something like this strstr, because it'll be much simpler that way. I'll do this in C, because it seems you like C strings anyway...

Code:

---

while( fgets( buf, BUFSIZ, file ) != NULL )
{
    if( strstr( buf, "-CD-" ) )
    {
        //we've found the CD line, so just skip it or make a new record
        //or whatever it is you've decided to do. I'll skip it.
        continue;
    }
    if( strstr( buf, "Artist:" ) )
    {
        //Ok, we've got a line starting (or at least containing) "Artist:"
        //Do something with it...
    }
    ...
}

---

And so on. You can even simplify it further if you know your data won't be screwed up.

Code:

---

while( fgets( buf, BUFSIZ, file ) != NULL )
{
    if( !strstr( buf, "-CD-" ) )
        continue; // It's NOT found, so keep looking...

    fgets( artistbuffer, BUFSIZ, file );
    fgets( titlebuffer, BUFSIZ, file );
    fgets( yearbuffer, BUFSIZ, file );
    //now peel off the first part of each and copy them where you want
}

---

But again, this works if you're using records which won't ever be "broken" or incorrect. You could of course skip those three fgets lines and use something like fscanf to read past the "tag"/prefix, and then use fgets to pick up from there.

Or you could use some of the *stream functions instead of C sytle functions to read your file.

At any rate, I'd suggest rethinking how you're doing it, because as I've stated, you're overcomplicating the issue.

Quzah.

Check this out swayp, you shall be brought to shore once again:

Code:

---

/*
  WARNING: I used goto, goto is bad.  I used goto because I was too lazy
  to understand the logicalness of the while() loop
*/

#include <iostream>
#include <fstream>
#include <string>
#include <vector>

using std::cout;
using std::endl;
using std::ifstream;
using std::string;
using std::vector;

// Extract tags from text file
string extractTag( ifstream * in, string startAfter, string endWhen );


int main( )
{
  // sz = the temperary string that gets extracted from the stream
  // szT = the temperary string that works with the tag innards

  string sz;
  string szT;

  // Create and open an input stream to the CD database

  ifstream in;
  in.open( "CDdb.txt" );

  // Make sure the CD database opened successfully

  if( !in.is_open( ) )
  {
      cout << "Could not open file" << endl;
      return 1;
  }

  // Prepare all of the information for the database
  // A = Artists
  // T = Title of CD
  // Y = Year of CD

  vector<string> A;
  vector<string> T;
  vector<string> Y;

  // Read all of the information from the CD database:

  while( !in.eof( ) )
  {
      // Extract Artist tag

      sz = extractTag( &in, "Artist:", "Title:" );
      if( sz.empty( ) )
        break;
      A.push_back( sz );

      // Extract Title tag:

      sz = extractTag( &in, "", "Year:" );
      if( sz.empty( ) )
        break;
      T.push_back( sz );

      // Extract Year tag:

      sz = extractTag( &in, "", "-CD-" );
      if( sz.empty( ) )
        break;
      Y.push_back( sz );
  }

  // Close the file stream

  in.close( );

  // Output all of the artists, titles, and years

  cout << "Artists: " << endl;
  for( size_t i = 0; i < A.size( ); i++ )
    cout << A[i] << endl;

  cout << "------------\nTitles: " << endl;
  for( size_t i = 0; i < T.size( ); i++ )
    cout << T[i] << endl;

  cout << "------------\nYears: " << endl;
  for( size_t i = 0; i < Y.size( ); i++ )
    cout << Y[i] << endl;

  // Return successfully

  return 0;
}


// Extract tags from text file
string
extractTag ( ifstream * in, // The stream we're extracting data from
            string s,      // Start extracting data after this string
            string e )      // Stop extracting data once we hit this "other" tag
{
  // sz = Create a string for comparing when we need to start extracting
  // szM = The master string that we return back as the tag's innards

  string sz;
  string szM;

  // Start extracting until we hit the start extracting string
  // Make sure the starting isn't empty though, that means we
  // just start scanning for tag innards immediately

  if( s.empty( ) )
    goto SkipThisBS;
  while( ( *in ) >> sz )
  {
      if( !sz.compare( s ) )
        break;
  }
SkipThisBS:

  // Make sure the stream is not empty

  if( ( *in ).eof ( ) )
    return "";

  // Start extracting the real stuff until we hit the ending tag

  while( ( *in ) >> sz && sz != e )
    szM += sz;

  // Return the innards of the tag

  return szM;
}

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