Thread: File input/output question

I have been slaving over this for hours. Why is the following code:

Code:

#include <stdio.h>


struct players
{
	char name[100];
	char position[100];
	double points;
	double steals;
	double blocks;
	double rebounds;
};

struct players nba[100];


int main()
{
	FILE *ifp, *ofp;
	char inputFile[100];
	char outputFile[100];
	int numberPlayers;
	
	printf("What is the name of the input file?\n");
	scanf("%s", inputFile);

	
	printf("What is the name of the output file?\n");
	scanf("%s", outputFile);
	
	ifp = fopen("players.txt", "r");
	
	fscanf(ifp, "%d", &numberPlayers);
	
	fclose(ifp);
	fclose(ofp);	

	return 0;
}

Returning this error:

Code:

 0 [main] a 3060 handle_exceptions: Exception: STATUS_ACCESS_VIOLATION
  10000 [main] a 3060 stackdump: Dumping stack trace to a.exe.stackdump

 ----jGRASP cygwin wedge2: process died on signal 11.
 ----jGRASP: operation complete.

I know it must be something simple that I'm doing, but I just cannot seem to figure it out. If you guys could help me I'd love you forever.

Your runtime error is probably caused by the following statement. It has no corresponding fopen statement.

Code:

fclose(ofp);

I took that out, I get the same error.

Your code runs fine for me when I comment out the offending statement. If I uncomment the offending statement, I get a runtime error.

It compiles, but when I run it (with the players.txt file that contains only "10") I get the error

Did you check that the result of the fopen call was non-null? (that is, the file opened successfully)

Bob is correct in that fclose(ofp) will result in undefined behaviour, since ofp has not been initialised.

I tried using "10" in players.txt and it works fine. The only other thing that comes to mind is that possibly the scanf's having a problem with the input variables. There may be some "junk" in these variables. So, you may want to clear them out prior to using them.

Bob

Code:

char inputFile[100]= {0};
char outputFile[100] = {0};

The contents of inputFile and outputFile don't matter, since the OP used scanf on them to write to them before any other use.

As I said above, there are two problems with the program that could cause problems:

1. As you said, fclose(ofp); where ofp is not initialised.
2. Not checking that the fopen was successful.

Yes, it's NULL, which means the file didn't open successfully. When fopen fails, look at strerror(errno) to see why it failed. Example:

Code:

/* additional headers at the top */
#include <string.h> /* for strerror */
#include <errno.h> /* for errno */

/* ... */

ifp = fopen("player.txt", "r");
if (ifp == NULL)
{
    fprintf(stderr, "Could not open file, reason: %s\n", strerror(errno));
    exit(1);
}

Sorry guys for waisting your time. Windows made the name players.txt.txt

grrrr, I knew it was something stupid.

Yup, Windows is pretty stupid. :-)

Check the return anyway, like I suggested above, it's a good habit.

Thanks for your help. I'll put it in my program.