How to parse XML file in C?

[harris21]

i have a XML file containing data, i want to parse it in c. can you help me out in parsing.

[N1GHTS]

I use the expat library in my application.

http://expat.sourceforge.net

Its robust, easy to use, open source, and recommended by the XML organization. I highly recommend it.

It uses callback functions, so what you do is open your file with fopen, then loop through each character and feed it to XML_Parse() like this...

int Parse(FILE *in_Stream) {

  XML_Parser p = XML_ParserCreate(NULL);
  if (! p) {
    fprintf(stderr, "Couldn't allocate memory for parser\n");
    return -1;
  }

  XML_UseParserAsHandlerArg(p);
  XML_SetElementHandler(p, start_hndl, end_hndl);
  XML_SetCharacterDataHandler(p, char_hndl);
  XML_SetProcessingInstructionHandler(p, proc_hndl);

  char buff;
  int  done = 0;
  for (fread(&buff, sizeof(char), 1, in_Stream); !feof(in_Stream); fread(&buff, sizeof(char), 1, in_Stream))
     if (! XML_Parse(p, &buff, sizeof(char), done)) {
        fprintf(stderr, "Parse error at line %d:\n%s\n",
          XML_GetCurrentLineNumber(p),
          XML_ErrorString(XML_GetErrorCode(p)));
        return -1;
     }
  return 0;

}

Then you use its callback functions to deal with the individual elements. The XML_Parse() function will call those event functions as soon as it detects that a new complete element has been received.

For instance, start_hndl() is called by the XML engine to tell you when something like "<Image" is found. It gives you the string "Image". If it encounters a "/>" or the tag was formatted like this "</Image>", it will call end_hndl() passing the same name "Image", so you know which tag it belongs to.

The sample program that comes with the library should be very easy to understand.