Re: failing to use getdents system call on Linux

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Re^2: failing to use getdents system call on Linux by Corion (Patriarch) on Nov 06, 2016 at 19:45 UTC
But the logic in the Perl program is different. It subtracts from `$read` and shortens the buffer by the processed bytes. I think the Perl program could run into an infinite loop if `$read` becomes negative, but that doesn't seem to be the problem here...	[reply] [d/l] [select]
Re^3: failing to use getdents system call on Linux by Anonymous Monk on Nov 06, 2016 at 19:59 UTC
Aye, sorry, scratch my hasty that. The `syscall()` must return a good value. OP problem seems to be in the unpack template. Should try native types instead: "L!L!SZ*". Perl `L` is 4 bytes...	[reply] [d/l] [select]
Re^4: failing to use getdents system call on Linux by glasswalk3r (Friar) on Nov 07, 2016 at 19:07 UTC
Yup, the problem was with unpack indeed... I changed the line below from: `my ( $ino, $off, $len, $name ) = unpack( "LLSZ", $buf );` [download] To: `my ( $ino, $off, $len, $name ) = unpack( "L!L!SZ", $buf );` [download] And the program finally worked as expected: `[me@localhost ~]$ ./test2.pl -d sample/ \| head sample/xaaaaaaaaff sample/xaaaaaaabdu sample/xaaaaaaabjw sample/xaaaaaaaaos sample/xaaaaaaaalu sample/xaaaaaaaags sample/xaaaaaaabci sample/xaaaaaaabhy sample/xaaaaaaabjv sample/xaaaaaaaaxa` [download] All good, but some questions remains: What could have happened that cause this change in the system? Originally I didn't need to worry about that. Maybe some change related going from 32 to 64 bits platforms? How can I double check if I need to use "native" sizes with the unpack template? Besides the program malfunctions, of course. :-) Alceu Rodrigues de Freitas Junior --------------------------------- "You have enemies? Good. That means you've stood up for something, sometime in your life." - Sir Winston Churchill	[reply] [d/l] [select]
Re^3: failing to use getdents system call on Linux by glasswalk3r (Friar) on Nov 07, 2016 at 18:54 UTC
Oh yes, infinite loop is a problem here, since I'm getting 1 or zero from $len. Here is the updated code: Read more... (1361 Bytes) The part changed to Pod is exactly the one that put me in a "infinite" loop (probably not infinite, but long enough to create a very large file, but I killed the process once it reached GB). As you can see in the code, I used the same buffer size as in the C code... but results are the same: Read more... (3 kB) Alceu Rodrigues de Freitas Junior --------------------------------- "You have enemies? Good. That means you've stood up for something, sometime in your life." - Sir Winston Churchill	[reply] [d/l] [select]