obtaing File Format in java/ DOS-UNIX

Question

Is there an easy way to see whether particular file has DOS/MAC/UNIX line endings?

Currently i read the file byte by byte and stop if i see Windows carriage return

for (byte thisByte : bytes) {

  if ((!isDos) && (thisByte == 13)) {
      isDos = true;
  }
...

Is there a way to get same information without reading file byte by byte?

Thank you.

Answer 1

If you know that a file only uses one sort of end-of-line, then you can just scan for the first newline and see if it's DOS/UNIX/Mac.

Answer 2

Assuming that it's a text file, and the lines are "reasonable" length, you could read a large block of the file (say 4096 bytes) and scan just that block for the CR character.

But otherwise, no, the only way that you can find a character in a file is to actually read the entire file and look for the character.

On the assumption that you're asking this question because you have performance problems reading the file a byte at a time: make sure that you wrap the FileInputStream with a BufferedInputStream.

Answer 3

A possible optimization might be to look only at the very final one or two bytes of the file. Since many text files terminate in a line ending this should work most of the time. If you don't spot a line ending there, then you'll have to fall back to byte-by-byte.

BTW, your example code sets isDos to true without checking if the very next character is a decimal 10. If it isn't a 10 then it's probably a MAC file format.