When under the C<use filetest 'access'> the above-mentioned filetests
will test whether the permission can (not) be granted using the
-access() family of system calls. Also note that the -x and -X may
+access() family of system calls. Also note that the C<-x> and C<-X> may
under this pragma return true even if there are no execute permission
bits set (nor any extra execute permission ACLs). This strangeness is
due to the underlying system calls' definitions. Read the
might be inherited by a derived class. See L<perltoot> and L<perlobj>
for more about the blessing (and blessings) of objects.
+Creating objects in lowercased CLASSNAMEs should be avoided. Such
+namespaces should be considered reserved for Perl pragmata and objects
+that may be created to implement internal operations.
+
+See L<perlmod/"Perl Modules">.
+
=item caller EXPR
=item caller
=item continue BLOCK
Actually a flow control statement rather than a function. If there is a
-C<continue> BLOCK attached to a BLOCK (typically in a L<(while> or
+C<continue> BLOCK attached to a BLOCK (typically in a L</while> or
L</foreach>), it is always executed just before the conditional is about to
be evaluated again, just like the third part of a L</for> loop in C. Thus
it can be used to increment a loop variable, even when the loop has been
false; you may wish to avoid constructs like C<while ($k = each %foo) {}>
for this reason.)
-Entries are returned in an apparently random order. When the hash is
-entirely read, a null array is returned in list context (which when
-assigned produces a FALSE (C<0>) value), and C<undef> in
+Entries are returned in an apparently random order. The actual random
+order is subject to change in future versions of perl, but it is guaranteed
+to be in the same order as either the C<keys()> or C<values()> function
+would produce on the same (unmodified) hash.
+
+When the hash is entirely read, a null array is returned in list context
+(which when assigned produces a FALSE (C<0>) value), and C<undef> in
scalar context. The next call to C<each()> after that will start iterating
again. There is a single iterator for each hash, shared by all C<each()>,
C<keys()>, and C<values()> function calls in the program; it can be reset by
print "$key=$value\n";
}
-See also C<keys()> and C<values()>.
+See also C<keys()>, C<values()> and C<sort()>.
=item else BLOCK
Returns a list consisting of all the keys of the named hash. (In a
scalar context, returns the number of keys.) The keys are returned in
-an apparently random order, but it is the same order as either the
-C<values()> or C<each()> function produces (given that the hash has not been
-modified). As a side effect, it resets HASH's iterator.
+an apparently random order. The actual random order is subject to
+change in future versions of perl, but it is guaranteed to be the same
+order as either the C<values()> or C<each()> function produces (given
+that the hash has not been modified). As a side effect, it resets
+HASH's iterator.
Here is yet another way to print your environment:
keys %hash = 200;
-then C<%hash> will have at least 200 buckets allocated for it--256 of them, in fact, since
-it rounds up to the next power of two. These
+then C<%hash> will have at least 200 buckets allocated for it--256 of them,
+in fact, since it rounds up to the next power of two. These
buckets will be retained even if you do C<%hash = ()>, use C<undef
%hash> if you want to free the storage while C<%hash> is still in scope.
You can't shrink the number of buckets allocated for the hash using
C<keys()> in this way (but you needn't worry about doing this by accident,
as trying has no effect).
+See also C<each()>, C<values()> and C<sort()>.
+
=item kill LIST
Sends a signal to a list of processes. The first element of
NOTE: On any operation that may do a fork, any unflushed buffers remain
unflushed in both processes, which means you may need to set C<$|> to
-avoid duplicate output.
+avoid duplicate output. On systems that support a close-on-exec flag on
+files, the flag will be set for the newly opened file descriptor as
+determined by the value of $^F. See L<perlvar/$^F>.
Closing any piped filehandle causes the parent process to wait for the
child to finish, and returns the status value in C<$?>.
See L<IPC::Open2>, L<IPC::Open3>, and L<perlipc/"Bidirectional Communication">
for examples of such things.
+On systems that support a close-on-exec flag on files, the flag will be set
+for the newly opened file descriptors as determined by the value of $^F.
+See L<perlvar/$^F>.
+
=item pop ARRAY
=item pop
=item qw/STRING/
-Generalized quotes. See L<perlop>.
+Generalized quotes. See L<perlop/"Regexp Quote-Like Operators">.
=item quotemeta EXPR
implementation for the variable. VARIABLE is the name of the variable
to be enchanted. CLASSNAME is the name of a class implementing objects
of correct type. Any additional arguments are passed to the "C<new()>"
-method of the class (meaning C<TIESCALAR>, C<TIEARRAY>, or C<TIEHASH>).
-Typically these are arguments such as might be passed to the C<dbm_open()>
-function of C. The object returned by the "C<new()>" method is also
-returned by the C<tie()> function, which would be useful if you want to
-access other methods in CLASSNAME.
+method of the class (meaning C<TIESCALAR>, C<TIEHANDLE>, C<TIEARRAY>,
+or C<TIEHASH>). Typically these are arguments such as might be passed
+to the C<dbm_open()> function of C. The object returned by the "C<new()>"
+method is also returned by the C<tie()> function, which would be useful
+if you want to access other methods in CLASSNAME.
Note that functions such as C<keys()> and C<values()> may return huge lists
when used on large objects, like DBM files. You may prefer to use the
A class implementing a hash should have the following methods:
TIEHASH classname, LIST
- DESTROY this
FETCH this, key
STORE this, key, value
DELETE this, key
+ CLEAR this
EXISTS this, key
FIRSTKEY this
NEXTKEY this, lastkey
+ DESTROY this
A class implementing an ordinary array should have the following methods:
TIEARRAY classname, LIST
- DESTROY this
FETCH this, key
STORE this, key, value
- [others TBD]
+ FETCHSIZE this
+ STORESIZE this, count
+ CLEAR this
+ PUSH this, LIST
+ POP this
+ SHIFT this
+ UNSHIFT this, LIST
+ SPLICE this, offset, length, LIST
+ EXTEND this, count
+ DESTROY this
+
+A class implementing a file handle should have the following methods:
+
+ TIEHANDLE classname, LIST
+ READ this, scalar, length, offset
+ READLINE this
+ GETC this
+ WRITE this, scalar, length, offset
+ PRINT this, LIST
+ PRINTF this, format, LIST
+ CLOSE this
+ DESTROY this
A class implementing a scalar should have the following methods:
TIESCALAR classname, LIST
- DESTROY this
FETCH this,
STORE this, value
+ DESTROY this
+
+Not all methods indicated above need be implemented. See L<perltie>,
+L<Tie::Hash>, L<Tie::Array>, L<Tie::Scalar> and L<Tie::Handle>.
Unlike C<dbmopen()>, the C<tie()> function will not use or require a module
for you--you need to do that explicitly yourself. See L<DB_File>
Returns a list consisting of all the values of the named hash. (In a
scalar context, returns the number of values.) The values are
-returned in an apparently random order, but it is the same order as
-either the C<keys()> or C<each()> function would produce on the same hash.
+returned in an apparently random order. The actual random order is
+subject to change in future versions of perl, but it is guaranteed to
+be the same order as either the C<keys()> or C<each()> function would
+produce on the same (unmodified) hash.
+
As a side effect, it resets HASH's iterator. See also C<keys()>, C<each()>,
and C<sort()>.
https://perl5.git.perl.org / perl5.git / blobdiff