See also exit(), warn(), and the Carp module.
-If LIST is empty and C<$@> already contains a value (typically from a
+If the output is empty and C<$@> already contains a value (typically from a
previous eval) that value is reused after appending C<"\t...propagated">.
This is useful for propagating exceptions:
eval { ... };
die unless $@ =~ /Expected exception/;
-If LIST is empty and C<$@> contains an object reference that has a
+If the output is empty and C<$@> contains an object reference that has a
C<PROPAGATE> method, that method will be called with additional file
and line number parameters. The return value replaces the value in
C<$@>. i.e. as if C<< $@ = eval { $@->PROPAGATE(__FILE__, __LINE__) }; >>
=item package NAMESPACE
X<package> X<module> X<namespace>
-=item package
-
Declares the compilation unit as being in the given namespace. The scope
of the package declaration is from the declaration itself through the end
of the enclosing block, file, or eval (the same as the C<my> operator).
Reads from the filehandle whose typeglob is contained in EXPR (or from
*ARGV if EXPR is not provided). In scalar context, each call reads and
returns the next line, until end-of-file is reached, whereupon the
-subsequent call returns undef. In list context, reads until end-of-file
+subsequent call returns C<undef>. In list context, reads until end-of-file
is reached and returns a list of lines. Note that the notion of "line"
used here is however you may have defined it with C<$/> or
C<$INPUT_RECORD_SEPARATOR>). See L<perlvar/"$/">.
-When C<$/> is set to C<undef>, when readline() is in scalar
+When C<$/> is set to C<undef>, when C<readline> is in scalar
context (i.e. file slurp mode), and when an empty file is read, it
returns C<''> the first time, followed by C<undef> subsequently.
$line = <STDIN>;
$line = readline(*STDIN); # same thing
-If readline encounters an operating system error, C<$!> will be set with the
-corresponding error message. It can be helpful to check C<$!> when you are
-reading from filehandles you don't trust, such as a tty or a socket. The
-following example uses the operator form of C<readline>, and takes the necessary
-steps to ensure that C<readline> was successful.
+If C<readline> encounters an operating system error, C<$!> will be set
+with the corresponding error message. It can be helpful to check
+C<$!> when you are reading from filehandles you don't trust, such as a
+tty or a socket. The following example uses the operator form of
+C<readline> and dies if the result is not defined.
- for (;;) {
- undef $!;
- unless (defined( $line = <> )) {
- last if eof;
- die $! if $!;
+ while ( ! eof($fh) ) {
+ defined( $_ = <$fh> ) or die "readline failed: $!";
+ ...
+ }
+
+Note that you have can't handle C<readline> errors that way with the
+C<ARGV> filehandle. In that case, you have to open each element of
+C<@ARGV> yourself since C<eof> handles C<ARGV> differently.
+
+ foreach my $arg (@ARGV) {
+ open(my $fh, $arg) or warn "Can't open $arg: $!";
+
+ while ( ! eof($fh) ) {
+ defined( $_ = <$fh> )
+ or die "readline failed for $arg: $!";
+ ...
}
- # ...
}
-
+
=item readlink EXPR
X<readlink>
default, empty leading fields are preserved, and empty trailing ones are
deleted. (If all fields are empty, they are considered to be trailing.)
-In scalar context, returns the number of fields found and splits into
-the C<@_> array. Use of split in scalar context is deprecated, however,
-because it clobbers your subroutine arguments.
+In scalar context, returns the number of fields found.
If EXPR is omitted, splits the C<$_> string. If PATTERN is also omitted,
splits on whitespace (after skipping any leading whitespace). Anything
system(@args) == 0
or die "system @args failed: $?"
-If you'd like to manually inspect C<system>'s failure, u can check all
+If you'd like to manually inspect C<system>'s failure, you can check all
possible failure modes by inspecting C<$?> like this:
if ($? == -1) {
not end in a newline, it appends the same file/line number text as C<die>
does.
-If LIST is empty and C<$@> already contains a value (typically from a
+If the output is empty and C<$@> already contains a value (typically from a
previous eval) that value is used after appending C<"\t...caught">
to C<$@>. This is useful for staying almost, but not entirely similar to
C<die>.
projects / p5sagit/p5-mst-13.2.git / blobdiff