C reading binary data file

I'm trying to write code to read a binary file into a buffer, then write the buffer to another file. I have the following code, but the buffer only stores a couple of ASCII characters from the first line in the file and nothing else. I got this from the web.

I can't find my original source on this:. You need to use "length" that you already established instead. Full Source code can be found here. Having a smaller buffer size would be helpful in copying tiny files. Even "char buffer[2]" would do the job. But noskipws makes all the characters transferred. So this will not only copy a text file but also a binary file. And stream uses buffer internally, I assume the speed won't be slow.

Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Reading and writing binary file Ask Question. Asked 10 years, 9 months ago. Active 11 months ago. Viewed k times. Only one block is requested. Changing the one into ten will read in ten blocks of x bytes at once. In this example we declare a structure rec with the members x,y and z of the type integer. In the main function we open fopen a file for writing w.

Then we check if the file is open, if not, an error message is displayed and we exit the program. Then we write the record to the file. We do this ten times, thus creating ten records. Take a look at the example:. With the fread we read-in the records one by one. After we have read the record we print the member x of that record. The only thing we need to explain is the fseek option. The function fseek must be declared like this:. The fseek function sets the file position indicator for the stream pointed to by the stream.

The new position, measured in characters from the beginning of the file, is obtained by adding offset to the position specified by whence. Three macros are declared in stdio.

Using negative numbers it is possible to move from the end of the file. In this example we are using fseek to seek the last record in the file. This counter is then used in the fseek statement to set the file pointer at the desired record. The result is that we read-in the records in the reverse order.

A last note: if you set the file position indicator to a position in a file and you want the first position in a file then you can use the function rewind to the first position in the file.

The function rewind can be used like this:. With the fseek statement in this example we go to the end of the file. Then we rewind to first position in the file. Then read-in all records and print the value of member x.

Create a free Team What is Teams? Collectives on Stack Overflow. Learn more. Asked 8 years, 10 months ago. Active 2 months ago. Viewed 20k times. I want to write a program that opens the binary file and encrypts it using DES. But how can I read the binary file? Improve this question. Alternatively, we can use the read function that is essentially a system call underneath the hood.

Notice that read works on file descriptors; thus the file should be opened with the open system call. It takes additional two arguments denoting the void pointer where the read data will be stored and the number bytes to be read from the file.