Save binary file c

Open your logging file in binary mode "wb" as mode argument to fopen. Close the logging file. Improve this answer. Jonathan Leffler Jonathan Leffler k gold badges silver badges bronze badges. The 'short write The file name can be anything you like on Unix nothing obliges you to place text into a file named plaintext. On Windows, you might reasonably use a.

I don't know why you can't open the file. Is it for reading or writing that it fails? What's the error in errno strerror errno? Sign up or log in Sign up using Google. Sign up using Facebook. Sign up using Email and Password.

Post as a guest Name. Keep in mind that C thinks of everything in the disk file as blocks of bytes read from disk into memory or read from memory onto disk. C uses a file pointer, but it can point to any byte location in the file.

You therefore have to keep track of things. In this program, a structure description rec has been used, but you can use any structure description you want. You can see that fopen and fclose work exactly as they did for text files. The new functions here are fread , fwrite and fseek. The fread function takes four parameters:. One block of 12 bytes is requested. It would be just as easy to read blocks from disk into an array in memory by changing 1 to The fwrite function works the same way, but moves the block of bytes from memory to the file.

The fseek function moves the file pointer to a byte in the file. Generally, you move the pointer in sizeof struct rec increments to keep the pointer at record boundaries. You can use three options when seeking:. Several different options appear in the code above. This opens the file for reading and writing, which allows records to be changed. Reads a 4-byte signed integer from the current stream and advances the current position of the stream by four bytes.

Reads a string from the current stream. The string is prefixed with the length, encoded as an integer seven bits at a time. The BinaryWriter class is used to write binary data to a stream.

A BinaryWriter object is created by passing a FileStream object to its constructor. Clears all buffers for the current writer and causes any buffered data to be written to the underlying device. Writes a one-byte Boolean value to the current stream, with 0 representing false and 1 representing true. Writes a Unicode character to the current stream and advances the current position of the stream in accordance with the Encoding used and the specific characters being written to the stream.

Writes a character array to the current stream and advances the current position of the stream in accordance with the Encoding used and the specific characters being written to the stream. Writes an eight-byte floating-point value to the current stream and advances the stream position by eight bytes.

Writes a four-byte signed integer to the current stream and advances the stream position by four bytes. Writes a length-prefixed string to this stream in the current encoding of the BinaryWriter, and advances the current position of the stream in accordance with the encoding used and the specific characters being written to the stream.