Why unclosed file size is 4 bytes

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Why this code creates file with size 4 bytes, though file unclosed.

ofstream output("number.bin");
int16_t value = 2570;
output.write(reinterpret_cast<const char*>(&value), sizeof(value));

It's easier to understand if you know hexadecimal notation and about ASCII encoding.

The hexadecimal representation of decimal 2570 is 0x0a0a. The byte 0x0a is the ASCII value for newline \n.

Since you open the file in text mode, the system might translate single newlines into the platform-dependent newline sequence. On Windows newline in text-files are the carriage-return/newline combination \r\n.

So when you write the value 0x0a0a it's like you're writing two newlines which will each be translated into two bytes, for a total length of four bytes (\r\n\r\n).

To solve your problem you should open the file in binary mode, where all data written to the file will be written as-is without any translations.

ofstream output("number.bin", std::ios::binary);

On old Mac systems, OS9 and earlier, then newline was represented as carriage-return \r. So on such a system the amount of bytes written would be correct but the data inside the file would seem incorrect (in the file it would be 0x0d0d).

File size, The maximum file size in the FAT32 file system, for example, is 4,294,967,295 bytes, which is one byte less than four gibibytes. Conversion table. Traditional units� Windows File Explorer cannot display size in Bytes, I assume that is because most users would not have the knowledge to work in bytes Click the link below to download a really great small free utility called Treesize. Using that tool, you will instantly see everything File cannot show you, including a Byte column - as indicated below

You opened the file as a text file, probably on Windows. The number 2570 in hex is 0x0a0a, i.e. two 0x0a bytes, which corresponds to two newlines. When writing text files in windows, each newline is represented by two bytes \r\n, so you write four bytes instead of two.

Open the file as binary to fix this:

ofstream output("number.bin", std::ios::binary);

Unclosed file objects in deploy � Issue #455 � lektor/lektor � GitHub, There are what appear to be some unclosed file objects around line 736: Deploying 410 bytes 6370.00 bytes/sec total size is 24250704 speedup is 1087.72 Done! BufferedReader name=4> for line in git(['commit', '-qm',� This is because the file system rounds the size up to include any unused space left over in the last disk sector used by the file. (A sector is the smallest amount of space addressable by the file system. The size of a disk sectors is several hundred or several thousands bytes.)

Why unclosed file size is 4 bytes

This behavior is implementation specific.

From what I understand of the C++11 standard (see n3337), you cannot reliably predict the behavior.

It depends upon your operating system (could be different on Linux and on Windows), your file system (could be different on ext4, on VFAT, and on ZFS), your standard C++ library implementation (could be different with Clang standard library and GCC one), etc....

So several layers of code are involved. Each is adding implementation details. At last, IO is generally buffered. You may want to use std::flush

interjay, Why I'm getting False? -3.27. Why unclosed file size is 4 bytes, -0.51. adding and subtracting values in C, 0.00. File size measures the size of a computer file and is typically measured in bytes with a prefix. The smallest unit in computers is bit and comes from b inary dig it. A bit has only two digits - zero and one. The zero is also known as false (off) state and the one is known as true (on). The bits are combined in groups in order to form larger units.

Why some write-in-progress files report 0 byte but shrinking drive's , So their SFT entries are not closed. The "new" NTFS behaviour is that directory entries for a file, stored in each of the directories that has To ameliorate the dirty shutdown risk and to see the file size increasing as the file was written to, one� Such as: file name, size, full path, extension, directory name, is file read only or not, File creation date, updated date etc. Note: we can convert the size from bytes to KB, MB, and GB by dividing bytes by 1024, 1024x1024 and so on.

Errors and Warnings Reference Guide: List of the armcc error and , 6 : comment unclosed at end of file this warning because the multibyte character consists of more bytes than can fit into an int : By not declaring a size for the array in the structure, the compiler is not able to allocate a size of the structure. A zero-byte file means that there is no data being stored in the file and the length of the file also becomes zero. In other words, the file contains no any content that can be written and read. When a file becomes 0 bytes, it usually means that something goes wrong with the file system or storage device. 0 bytes files cannot be opened.

filesize - Manual, Returns the size of the file in bytes, or FALSE (and generates an error of level For file size over PHP_INT_MAX (2 147 483 647), PHP filesize function loops� No, it's typically 4 bytes if your program is compiled as a 32-bit program. It'll be 4 bytes if compiled as 32-bit but running on a 64-bit processor. It'll be 8 bytes if compiled as 64-bit. However! It can be bigger than that too.

Comments
  • How do you check the size? And when do you check the size? What happens inside your program between the three lines you show, and when you check the size? And please try to create a minimal reproducible example to show us. Also please take some time to read about how to ask good questions, as well as this question checklist.
  • open as binary ofstream output("number.bin", std::ios::binary);. And close the file before checking the size .
  • Think about buffering. What is it? What does it do?
  • I don't quite grok the relevance of whether the file is closed or not. Are you asking how buffering works? Are you asking what bytes are written to the file by this code? Be more clear.
  • @Peter: sizeof(int16_t) is commonly '2', not '4'. Although the question doesn't spell it out, this is likely the primary source of curiosity for the OP. That plus the automatic scope-based close that C++ applies.
  • This question from job interview. The exact question was "Which will be the output file size?" After the interview I run this code and see the result. As far as I understand this number converts(casts to char*) to two symbols of new line each of which is of size two bytes. Though we pass to write the size 2 bytes(sizeof int16)