[Caml-list] no tell on files?

[Caml-list] no tell on files?

[Chris Hecker]

There appears to be no "tell" function on pervasives streams or Unix
file descriptors.  Is there a reason for this?  The combination of
that plus the lack of a pervasives relative seek makes it hard to move
around in files without keeping parallel information.

Thanks,
Chris


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Re: [Caml-list] no tell on files?

[Ed L Cashin]

Chris Hecker <checker@d6.com> writes:

> There appears to be no "tell" function on pervasives streams or Unix
> file descriptors.  Is there a reason for this?  The combination of
> that plus the lack of a pervasives relative seek makes it hard to move
> around in files without keeping parallel information.

Seek is tell!  The program below gives this output:

  ecashin@meili seek-tell$ ./a.out 
  read 10 chars: " Unix.SEEK"



let main = 
  let fd = Unix.openfile "main.ml" [Unix.O_RDONLY] 0 in
  let end_pos = Unix.lseek fd 0 Unix.SEEK_END in
  let half_pos = Unix.lseek fd (end_pos/2) Unix.SEEK_SET and
      buf = String.create 1024 in
  Printf.printf "read %d chars: \"%s\"\n"
    (UnixLabels.read fd ~buf ~pos:0 ~len:10)
    buf  
;;

main

-- 
--Ed L Cashin            |   PGP public key:
  ecashin@uga.edu        |   http://noserose.net/e/pgp/
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Re: [Caml-list] no tell on files?

[Chris Hecker]

>Seek is tell!

Aha!  It's undocumented, but now I notice the "-> int" on the call!

And I just noticed pos_in|out in the pervasives.  I swear it wasn't there 
this afternoon.  I looked, really!  :)

I'm a dork!

Sorry for wasting bandwidth and time, and thanks!

Chris

PS.  Maybe the docs for Unix and Pervasives should have the word "tell" in 
them so that a text search can find these functions for "c people".


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