How to read a binary file in c? (video, images, or text)
Question
I am trying to copy a file from a specified library to the current directory. I can copy text files perfectly. Any other files become corrupt. The program detects a feof before it should.
#include <stdio.h>
int BUFFER_SIZE = 1024;
FILE *source;
FILE *destination;
int n;
int count = 0;
int written = 0;
int main() {
unsigned char buffer[BUFFER_SIZE];
source = fopen("./library/rfc1350.txt", "r");
if (source) {
destination = fopen("rfc1350.txt", "w");
while (!feof(source)) {
n = fread(buffer, 1, BUFFER_SIZE, source);
count += n;
printf("n = %d\n", n);
fwrite(buffer, 1, n, destination);
}
printf("%d bytes read from library.\n", count);
} else {
printf("fail\n");
}
fclose(source);
fclose(destination);
return 0;
}
Solution
Are you on a Windows machine? Try adding "b" to the mode strings in the calls to fopen
.
From man fopen(3):
The mode string can also include the letter 'b' either as a last character or as a character between the characters in any of the two-character strings described above. This is strictly for compatibility with C89 and has no effect; the 'b' is ignored on all POSIX conforming systems, including Linux. (Other systems may treat text files and binary files differently, and adding the 'b' may be a good idea if you do I/O to a binary file and expect that your program may be ported to non-Unix environments.)
OTHER TIPS
You need to specify the "b"
option to fopen
:
source = fopen("./library/rfc1350.txt", "rb");
...
destination = fopen("rfc1350.txt", "wb");
Without it, the file is opened in text ("t"
) mode, and this results in translation of end-of-line characters.
You need to open the files in binary format rather than text format. In your calls to fopen
, use "rb"
and "wb"
rather than "r"
and "w"
respectively.
Licensed under: CC-BY-SA with attribution
Not affiliated with StackOverflow