Programming

char buf[1024];
char *token="<field=\"tmp\">", *match;

strcpy(buf, "<field=\"tmp\">replace me</field>");

// Gives us NULL if no match, or the position of the first match
match=strstr(buf, token);
if(match)
{
        // Move past the token
        match+=strlen(token);
        // Overwrite EVERYTHING after the token
        sprintf(match, "%s</field>\n", "replacement value");
}

//Global Declarations
char sSearchString[1024] = {0,};
char *result;

FILE *istream;
while(!feof(istream)) //main loop
{
	char this_line[256];
	fgets (this_line, sizeof(this_line), istream);
	sprintf(sSearchString, "<field name=\"tmp\">");

	result=strstr(this_line, sSearchString);
	if(result) //we are in the media table
	{
		result+=strlen(sSearchString);
		sprintf(result, "%s</field>\n", newtmp);
		sprintf(this_line, "%s", result);
	}

	//print to new file
	FILE *fout = fopen("new.xml","a");
	if(fout == NULL)
	{
		fclose(fout);
		return false;
	}
	fprintf(fout,"%s",this_line);
	fclose(fout);
}

sprintf(this_line, "%s", result);