Just for completeness:

4) I don't know how these test cases were generated.

The windows text file was generated using the Notepad application on Windows 7, on a Samba share mapped as drive H: from a Slackware Linux 14.1 server. The Linux file was generated using joe on the Linux server. The old Mac file was generated by using Notepad++ on the Windows machine (I have no old Mac). Re^5: Regular expressions across multiple lines shows the hexdumps of the files.

There is no way to do that without being in Perl bin mode or writing a C program.

With my setup, there is a way to generate all three files on Linux, without using binmode. This trick abuses the fact that there is absolutely no difference between text mode and binary mode on unix:

/tmp/demo2>cat three-os.pl
#!/usr/bin/perl

use strict;
use warnings;

open OUT,'>','unix.txt' or die "unix.txt: $!";
print OUT "line 1\x0Aline 2\x0Aline 3\x0A";
close OUT;

open OUT,'>','oldmac.txt' or die "oldmac.txt: $!";
print OUT "line 1\x0Dline 2\x0Dline 3\x0D";
close OUT;

open OUT,'>','windows.txt' or die "windows.txt: $!";
print OUT "line 1\x0D\x0Aline 2\x0D\x0Aline 3\x0D\x0A";
close OUT;

exec "file *.txt" or die "exec failed: $!";

/tmp/demo2>perl three-os.pl
oldmac.txt:  ASCII text, with CR line terminators
unix.txt:    ASCII text
windows.txt: ASCII text, with CRLF line terminators

/tmp/demo2>
[download]

This won't work on Windows, because for C and Perl on Windows, \n and \x0A are equal. Then, text mode translation happens and every \x0A is replaced with CRLF. Running the same script on Windows (again using the Samba share) will complain about a missing "file" utility and gives this result:

/tmp/demo2>file *.txt
oldmac.txt:  ASCII text, with CR line terminators
unix.txt:    ASCII text, with CRLF line terminators
windows.txt: ASCII text, with CRLF, CR line terminators

/tmp/demo2>od -tx1 -c windows.txt
0000000  6c  69  6e  65  20  31  0d  0d  0a  6c  69  6e  65  20  32  0
+d
          l   i   n   e       1  \r  \r  \n   l   i   n   e       2  \
+r
0000020  0d  0a  6c  69  6e  65  20  33  0d  0d  0a
         \r  \n   l   i   n   e       3  \r  \r  \n
0000033

/tmp/demo2>
[download]

The output from the file utility is a little bit misleading. The lines in windows.txt are terminated by CR CR LF, this can be seen in the output of od.

Alexander