Re: [MacPerl] File reading ?'s

[Vicki Brown <vlb@cfcl.com>]

> >From "Perl 5 for Dummies":
>
> "read(HANDLE, VARIABLE, LENGTH, POSITION);
>
> The Variable is the place where you want to read into, the length is the
> number of bytes to read, and the position is the byte in the file to
> start reading from."
>
> it says that if you leave the Position empty, then it uses the current
> file position, but if you put a number there, that is the starting point.
>  Is this totally wrong?

Youch.  Close enough to confuse.  According to the POD (or the Camel, take
your pick)  OFFSET (aka POSITION) isn't the position in the file to start
reading from, it's the position in the scalar to read _to_.  A subtle
difference but a major one!


	read FILEHANDLE,SCALAR,LENGTH,OFFSET

Attempts to read LENGTH bytes of data into variable SCALAR from the
specified FILEHANDLE.  Returns the number of bytes actually read, or undef
if there was an error.  ...  An OFFSET may be specified to place the read
data at some other place than the beginning of the string.

> Is "read" only meant for Text
> files, and "sysread" for binary files?  Can you do a regular "open"
> command, and then do a "sysread"?

Open is unrelated to the choice of read vs. sysread; open simply gets you
the FILEHANDLE.  Perl's read is implemented with the Standard I/O function;
sysread isn't.  Schools of thought differ on whether to use Standard I/O
(which handles some magic for you) or not. My school of thought says there
is nothing wrong with using read :-)
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