marty@wuphys.wustl.edu (Marty Olevitch) (03/01/91)
Well, now that "Programming Perl" is available, I have learned
enough to get quite confused! I've been converting a few
of my little C utilities into perl, and ran into this problem.
Say I have an array of (open) file handles @handle. Then if I try
for($i = 0; $i <= $#handle; $i++) {
$line = <$handle[$i]>;
}
it doesn't put the next line from the file into $line, but
rather the name of the file handle (and seems to miss every other
one). However, the following:
for($i = 0; $i <= $#handle; $i++) {
$filehandle = $handle[$i];
$line = <$filehandle>;
}
does read the next line into $line. Is this the way it is supposed to
work? This is using perl 3.0 at patchlevel 44.
Also, I found that using the <> operator with an array argument,
for example <@foo> , reads the next item in the foo array. But I didn't
see this documented in the perl book, at least where the main discussion
of the input operator takes place. Going back to the first example,
does perl think that $handle[$i] is supposed to be an array?
Marty Olevitch Internet: marty@wuphys.wustl.edu
Washington University UUCP: uunet!wugate!wuphys!marty
Physics Department, Campus Box 1105 Bitnet: marty@wuphys.WUSTL
St Louis MO 63130 USA Tel: (314) 889-6285lwall@jpl-devvax.JPL.NASA.GOV (Larry Wall) (03/02/91)
In article <1991Feb28.171434.6125@wuphys.wustl.edu> marty@wuphys.UUCP (Marty Olevitch) writes:
: Also, I found that using the <> operator with an array argument,
: for example <@foo> , reads the next item in the foo array. But I didn't
: see this documented in the perl book, at least where the main discussion
: of the input operator takes place. Going back to the first example,
: does perl think that $handle[$i] is supposed to be an array?
No, it thinks it's a glob. The only kind of indirect filehandle allowed
is a bare scalar variable with no intervening whitespace:
<$indirect_filehandle>
Anything else is a glob (interpreted like a double-quoted string first).
It could be argued that <> is too heavily overloaded, but it's nice to be
able to say:
while (<$dir/*.bak>) { ...
Larry