File I/O stopped working.

Strange occurence when working with file input output:

Here is my code.

Code:

---

#include <stdio.h>
int main()
{
FILE *fp;
fp=fopen("c:\\test.txt", "wb");
char x[10]="ABCDEFGHIJ";
fwrite(x, sizeof(x[0]), sizeof(x)/sizeof(x[0]), fp);
system("Pause");
}

---

Here is what she looks like when compiling.

Code:

---

Microsoft (R) 32-bit C/C++ Optimizing Compiler Version 16.00.30319.01 for 80x86
Copyright (C) Microsoft Corporation.  All rights reserved.
poop.c
poop.c(7) : error C2143: syntax error : missing ';' before 'type'
poop.c(8) : error C2065: 'x' : undeclared identifier
poop.c(8) : warning C4022: 'fwrite' : pointer mismatch for actual parameter 1
poop.c(8) : error C2065: 'x' : undeclared identifier
poop.c(8) : error C2109: subscript requires array or pointer type
poop.c(8) : error C2065: 'x' : undeclared identifier
poop.c(8) : error C2065: 'x' : undeclared identifier
poop.c(8) : error C2109: subscript requires array or pointer type
poop.c(8) : warning C4047: 'function' : 'size_t' differs in levels of indirectio
n from 'FILE *'
poop.c(8) : warning C4024: 'fwrite' : different types for formal and actual para
meter 2
poop.c(8) : error C2198: 'fwrite' : too few arguments for call

---

This was compiling and working previously. I am unsure of what happened and why. Thank you for your input on my output

Note: test.txt is located at C:\test.txt

Compiles and runs fine for me in GCC (although I've included 2 warnings below you should be aware of: C90 says you should declare all your varables before doing anything else, and you should explicitly return a value from main). So it's not a code problem - must be something to do with your environment, compiler invocation or configuration or something.

test.c:6:1: warning: ISO C90 forbids mixed declarations and code [-pedantic]
test.c:8:1: warning: control reaches end of non-void function [-Wreturn-type]

Code:

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char x[10]="ABCDEFGHIJ";

---

This likely isn't related to your problem, but you're not leaving room for the null character here.

[edit] Actually, I don't think that's strictly necessary if you're simply using it as a character array and not a string.

Why you opened new thread?

http://cboard.cprogramming.com/c-pro...on-sort-2.html

Quote:

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Originally Posted by Matticus

Code:

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char x[10]="ABCDEFGHIJ";

---

This likely isn't related to your problem, but you're not leaving room for the null character here.

---

In this case what will happen?The compiler cuts off the last letter or does not store the null terminator?

Quote:

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Originally Posted by std10093

In this case what will happen?The compiler cuts off the last letter or does not store the null terminator?

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I believe it was laserlight who pointed this out to me - I'm pretty sure it just doesn't not store the null character.

Proof:

Code:

---

#include <stdio.h>

int main(void)
{
    char charArray[10] = "ABCDEFGHIJ";
    int i;

    for(i=0; i<10; i++)
        printf("%c\n",charArray[i]);

    return 0;
}

---

My apologies for going off topic, I'll stop here.

Yes it is a problem, and should actually be caught by the compiler. The end of string character will be placed at the end of the string, which in this case will be past the boundary of the array.

Jim

- You need to include the stdlib.h header file in order to gain access to the system function.
- You ought to check the return value of fopen to ensure that the stream was opened successfully.
- You need to get a compiler that supports mixed declarations and code, such as GCC or Clang.

Quote:

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Originally Posted by jimblumberg

Yes it is a problem, and should actually be caught by the compiler. The end of string character will be placed at the end of the string, which in this case will be past the boundary of the array.

Jim

---

As Matticus said, C will not add a null terminator in that case. It's basically a non-null terminated array of char containing "ABCDEFGHIJ". It's a problem only if the code expects the null terminator to be there.

Thank you, christop. To verify, I found this in the "current draft of the C standard, containing C99" (at this link)

Quote:

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6.7.8 Initialization

32 EXAMPLE 8 The declaration

Code:

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char s[] = "abc", t[3] = "abc";

---

defines "plain" char array objects s and t whose elements are initialized with character string literals.
This declaration is identical to

Code:

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char s[] = { 'a', 'b', 'c', '\0' },
    t[] = { 'a', 'b', 'c' };

---

The contents of the arrays are modifiable.

---

Solved:

Something had to have been incorrect with my permissions on C: drive.

Tried switching to a desktop file which still returned failure.

This is the correct way to write code to files in C:

Code:

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C:\\users\\hello\\desktop\\text.txt

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// is the correct way to write /'s in file locations for all others who run into problems with file input output