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Michael Kraus wrote:
John,
Lighten up matey...
The examples I've given are just that examples... Error checking functionality is up the end programmer... (And you are quite right, you should check the status of operations.) This is a beginers list, let's keep it friendly, eh?
... and FWIW ...
for my $line (<INFILE>) { # stuff }
is equivalent to:
while (my $line = <INFILE>) { # stuff }
If you are going to correct me, at least get it right and do it in a friendly manner! ;) :P :)
perldoc -q "How can I make my Perl program take less memory" perldoc -q "How can I read in an entire file all at once"
perldoc perlop
[snip]
I/O Operators[snip]
The following lines are equivalent:
while (defined($_ = <STDIN>)) { print; }
while ($_ = <STDIN>) { print; }
while (<STDIN>) { print; }
for (;<STDIN>;) { print; }
print while defined($_ = <STDIN>);
print while ($_ = <STDIN>);
print while <STDIN>;[snip]
If a <FILEHANDLE> is used in a context that is looking for a list, a
list comprising all input lines is returned, one line per list element.
It's easy to grow to a rather large data space this way, so use with
care.perldoc perlsyn
[snip]
Compound Statements In Perl, a sequence of statements that defines a scope is called a
block. Sometimes a block is delimited by the file containing it (in
the case of a required file, or the program as a whole), and sometimes
a block is delimited by the extent of a string (in the case of an
eval). But generally, a block is delimited by curly brackets, also known as
braces. We will call this syntactic construct a BLOCK.The following compound statements may be used to control flow:
if (EXPR) BLOCK
if (EXPR) BLOCK else BLOCK
if (EXPR) BLOCK elsif (EXPR) BLOCK ... else BLOCK
LABEL while (EXPR) BLOCK
^^^^
LABEL while (EXPR) BLOCK continue BLOCK
^^^^
LABEL for (EXPR; EXPR; EXPR) BLOCK
^^^^
LABEL foreach VAR (LIST) BLOCK
^^^^
LABEL foreach VAR (LIST) BLOCK continue BLOCK
^^^^
LABEL BLOCK continue BLOCK[ emphasis added ]
$ wc < test-file.txt
4328 10551 153707
$ perl -e'system "free","-ob"; while ( <> ) { system "free","-ob"; last }' test-file.txt
total used free shared buffers cached
Mem: 261013504 256503808 4509696 0 42680320 116006912
Swap: 348356608 5406720 342949888
total used free shared buffers cached
Mem: 261013504 256503808 4509696 0 42680320 116006912
Swap: 348356608 5406720 342949888
$ perl -le'print 256503808 - 256503808'
0
$ perl -e'system "free","-ob"; for ( <> ) { system "free","-ob"; last }' test-file.txt
total used free shared buffers cached
Mem: 261013504 256503808 4509696 0 42680320 116006912
Swap: 348356608 5406720 342949888
total used free shared buffers cached
Mem: 261013504 257056768 3956736 0 42680320 116006912
Swap: 348356608 5406720 342949888
$ perl -le'print 257056768 - 256503808'
552960
Michael S. E. Kraus
Software Developer
Wild Technology Pty Ltd
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John -- use Perl; program fulfillment
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