X<scalar> X<string> X<character>
C<chomp>, C<chop>, C<chr>, C<crypt>, C<hex>, C<index>, C<lc>, C<lcfirst>,
-C<length>, C<oct>, C<ord>, C<pack>, C<q/STRING/>, C<qq/STRING/>, C<reverse>,
+C<length>, C<oct>, C<ord>, C<pack>, C<q//>, C<qq//>, C<reverse>,
C<rindex>, C<sprintf>, C<substr>, C<tr///>, C<uc>, C<ucfirst>, C<y///>
=item Regular expressions and pattern matching
=item Functions for list data
X<list>
-C<grep>, C<join>, C<map>, C<qw/STRING/>, C<reverse>, C<sort>, C<unpack>
+C<grep>, C<join>, C<map>, C<qw//>, C<reverse>, C<sort>, C<unpack>
=item Functions for real %HASHes
X<hash>
=item Keywords related to switch
-C<break>, C<continue>
+C<break>, C<continue>, C<given>, C<when>, C<default>
(These are only available if you enable the "switch" feature.
See L<feature> and L<perlsyn/"Switch statements">.)
=item Keywords related to scoping
-C<caller>, C<import>, C<local>, C<my>, C<our>, C<package>, C<use>
+C<caller>, C<import>, C<local>, C<my>, C<our>, C<state>, C<package>,
+C<use>
+
+(C<state> is only available if the "state" feature is enabled. See
+L<feature>.)
=item Miscellaneous functions
-C<defined>, C<dump>, C<eval>, C<formline>, C<local>, C<my>, C<our>, C<reset>,
-C<scalar>, C<undef>, C<wantarray>
+C<defined>, C<dump>, C<eval>, C<formline>, C<local>, C<my>, C<our>,
+C<reset>, C<scalar>, C<state>, C<undef>, C<wantarray>
=item Functions for processes and process groups
X<process> X<pid> X<process id>
C<alarm>, C<exec>, C<fork>, C<getpgrp>, C<getppid>, C<getpriority>, C<kill>,
-C<pipe>, C<qx/STRING/>, C<setpgrp>, C<setpriority>, C<sleep>, C<system>,
+C<pipe>, C<qx//>, C<setpgrp>, C<setpriority>, C<sleep>, C<system>,
C<times>, C<wait>, C<waitpid>
=item Keywords related to perl modules
=item Functions new in perl5
X<perl5>
-C<abs>, C<bless>, C<chomp>, C<chr>, C<exists>, C<formline>, C<glob>,
-C<import>, C<lc>, C<lcfirst>, C<map>, C<my>, C<no>, C<our>, C<prototype>,
-C<qx>, C<qw>, C<readline>, C<readpipe>, C<ref>, C<sub*>, C<sysopen>, C<tie>,
-C<tied>, C<uc>, C<ucfirst>, C<untie>, C<use>
+C<abs>, C<bless>, C<break>, C<chomp>, C<chr>, C<continue>, C<default>,
+C<exists>, C<formline>, C<given>, C<glob>, C<import>, C<lc>, C<lcfirst>,
+C<lock>, C<map>, C<my>, C<no>, C<our>, C<prototype>, C<qr//>, C<qw//>, C<qx//>,
+C<readline>, C<readpipe>, C<ref>, C<sub>*, C<sysopen>, C<tie>, C<tied>, C<uc>,
+C<ucfirst>, C<untie>, C<use>, C<when>
* - C<sub> was a keyword in perl4, but in perl5 it is an
operator, which can be used in expressions.
=item -X EXPR
+=item -X DIRHANDLE
+
=item -X
A file test, where X is one of the letters listed below. This unary
-operator takes one argument, either a filename or a filehandle, and
-tests the associated file to see if something is true about it. If the
+operator takes one argument, either a filename, a filehandle, or a dirhandle,
+and tests the associated file to see if something is true about it. If the
argument is omitted, tests C<$_>, except for C<-t>, which tests STDIN.
Unless otherwise documented, it returns C<1> for true and C<''> for false, or
the undefined value if the file doesn't exist. Despite the funny
suitable for passing binary data. This includes turning off possible CRLF
translation and marking it as bytes (as opposed to Unicode characters).
Note that, despite what may be implied in I<"Programming Perl"> (the
-Camel) or elsewhere, C<:raw> is I<not> the simply inverse of C<:crlf>
--- other layers which would affect binary nature of the stream are
+Camel) or elsewhere, C<:raw> is I<not> simply the inverse of C<:crlf>
+-- other layers which would affect the binary nature of the stream are
I<also> disabled. See L<PerlIO>, L<perlrun> and the discussion about the
PERLIO environment variable.
of this version of Perl therefore refers to "layers" rather than to
"disciplines". Now back to the regularly scheduled documentation...>
-To mark FILEHANDLE as UTF-8, use C<:utf8>.
+To mark FILEHANDLE as UTF-8, use C<:utf8> or C<:encoding(utf8)>.
+C<:utf8> just marks the data as UTF-8 without further checking,
+while C<:encoding(utf8)> checks the data for actually being valid
+UTF-8. More details can be found in L<PerlIO::encoding>.
In general, binmode() should be called after open() but before any I/O
is done on the filehandle. Calling binmode() will normally flush any
we're in a subroutine or C<eval> or C<require>, and the undefined value
otherwise. In list context, returns
+ # 0 1 2
($package, $filename, $line) = caller;
With EXPR, it returns some extra information that the debugger uses to
print a stack trace. The value of EXPR indicates how many call frames
to go back before the current one.
+ # 0 1 2 3 4
($package, $filename, $line, $subroutine, $hasargs,
- $wantarray, $evaltext, $is_require, $hints, $bitmask) = caller($i);
+
+ # 5 6 7 8 9 10
+ $wantarray, $evaltext, $is_require, $hints, $bitmask, $hinthash)
+ = caller($i);
Here $subroutine may be C<(eval)> if the frame is not a subroutine
call, but an C<eval>. In such a case additional elements $evaltext and
compiled with. The C<$hints> and C<$bitmask> values are subject to change
between versions of Perl, and are not meant for external use.
+C<$hinthash> is a reference to a hash containing the value of C<%^H> when the
+caller was compiled, or C<undef> if C<%^H> was empty. Do not modify the values
+of this hash, as they are the actual values stored in the optree.
+
Furthermore, when called from within the DB package, caller returns more
detailed information: it sets the list variable C<@DB::args> to be the
arguments with which the subroutine was invoked.
=item chdir EXPR
X<chdir>
X<cd>
+X<directory, change>
=item chdir FILEHANDLE
On systems that support fchmod, you might pass file handles among the
files. On systems that don't support fchmod, passing file handles
-produces a fatal error at run time.
+produces a fatal error at run time. The file handles must be passed
+as globs or references to be recognized. Barewords are considered
+file names.
open(my $fh, "<", "foo");
my $perm = (stat $fh)[2] & 07777;
If you chomp a list, each element is chomped, and the total number of
characters removed is returned.
-If the C<encoding> pragma is in scope then the lengths returned are
-calculated from the length of C<$/> in Unicode characters, which is not
-always the same as the length of C<$/> in the native encoding.
-
Note that parentheses are necessary when you're chomping anything
that is not a simple variable. This is because C<chomp $cwd = `pwd`;>
is interpreted as C<(chomp $cwd) = `pwd`;>, rather than as
On systems that support fchown, you might pass file handles among the
files. On systems that don't support fchown, passing file handles
-produces a fatal error at run time.
+produces a fatal error at run time. The file handles must be passed
+as globs or references to be recognized. Barewords are considered
+file names.
Here's an example that looks up nonnumeric uids in the passwd file:
Returns the character represented by that NUMBER in the character set.
For example, C<chr(65)> is C<"A"> in either ASCII or Unicode, and
-chr(0x263a) is a Unicode smiley face. Note that characters from 128
-to 255 (inclusive) are by default not encoded in UTF-8 Unicode for
-backward compatibility reasons (but see L<encoding>).
+chr(0x263a) is a Unicode smiley face.
Negative values give the Unicode replacement character (chr(0xfffd)),
except under the L<bytes> pragma, where low eight bits of the value
For the reverse, use L</ord>.
-Note that under the C<bytes> pragma the NUMBER is masked to
-the low eight bits.
+Note that characters from 128 to 255 (inclusive) are by default
+internally not encoded as UTF-8 for backward compatibility reasons.
-See L<perlunicode> and L<encoding> for more about Unicode.
+See L<perlunicode> for more about Unicode.
=item chroot FILENAME
X<chroot> X<root>
=item close
-Closes the file or pipe associated with the file handle, returning
-true only if IO buffers are successfully flushed and closes the system
-file descriptor. Closes the currently selected filehandle if the
-argument is omitted.
+Closes the file or pipe associated with the file handle, flushes the IO
+buffers, and closes the system file descriptor. Returns true if those
+operations have succeeded and if no error was reported by any PerlIO
+layer. Closes the currently selected filehandle if the argument is
+omitted.
You don't have to close FILEHANDLE if you are immediately going to do
another C<open> on it, because C<open> will close it for you. (See
=item crypt PLAINTEXT,SALT
X<crypt> X<digest> X<hash> X<salt> X<plaintext> X<password>
-X<decrypt> X<cryptography> X<passwd>
+X<decrypt> X<cryptography> X<passwd> X<encrypt>
Creates a digest string exactly like the crypt(3) function in the C
library (assuming that you actually have a version there that has not
a more elaborate exception handling implementation using objects that
maintain arbitrary state about the nature of the exception. Such a scheme
is sometimes preferable to matching particular string values of $@ using
-regular expressions. Here's an example:
+regular expressions. Because $@ is a global variable, and eval() may be
+used within object implementations, care must be taken that analyzing the
+error object doesn't replace the reference in the global variable. The
+easiest solution is to make a local copy of the reference before doing
+other manipulations. Here's an example:
use Scalar::Util 'blessed';
eval { ... ; die Some::Module::Exception->new( FOO => "bar" ) };
- if ($@) {
- if (blessed($@) && $@->isa("Some::Module::Exception")) {
+ if (my $ev_err = $@) {
+ if (blessed($ev_err) && $ev_err->isa("Some::Module::Exception")) {
# handle Some::Module::Exception
}
else {
be open any more when the program is reincarnated, with possible
resulting confusion on the part of Perl.
-This function is now largely obsolete, partly because it's very
-hard to convert a core file into an executable, and because the
-real compiler backends for generating portable bytecode and compilable
-C code have superseded it. That's why you should now invoke it as
-C<CORE::dump()>, if you don't want to be warned against a possible
+This function is now largely obsolete, mostly because it's very hard to
+convert a core file into an executable. That's why you should now invoke
+it as C<CORE::dump()>, if you don't want to be warned against a possible
typo.
-If you're looking to use L<dump> to speed up your program, consider
-generating bytecode or native C code as described in L<perlcc>. If
-you're just trying to accelerate a CGI script, consider using the
-C<mod_perl> extension to B<Apache>, or the CPAN module, CGI::Fast.
-You might also consider autoloading or selfloading, which at least
-make your program I<appear> to run faster.
-
=item each HASH
X<each> X<hash, iterator>
=item eval EXPR
X<eval> X<try> X<catch> X<evaluate> X<parse> X<execute>
+X<error, handling> X<exception, handling>
=item eval BLOCK
C<formline> always returns true. See L<perlform> for other examples.
=item getc FILEHANDLE
-X<getc> X<getchar>
+X<getc> X<getchar> X<character> X<file, read>
=item getc
=item gmtime
-Converts a time as returned by the time function to an 9-element list
-with the time localized for the standard Greenwich time zone.
-Typically used as follows:
-
- # 0 1 2 3 4 5 6 7 8
- ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) =
- gmtime(time);
-
-All list elements are numeric, and come straight out of the C `struct
-tm'. $sec, $min, and $hour are the seconds, minutes, and hours of the
-specified time. $mday is the day of the month, and $mon is the month
-itself, in the range C<0..11> with 0 indicating January and 11
-indicating December. $year is the number of years since 1900. That
-is, $year is C<123> in year 2023. $wday is the day of the week, with
-0 indicating Sunday and 3 indicating Wednesday. $yday is the day of
-the year, in the range C<0..364> (or C<0..365> in leap years). $isdst
-is always C<0>.
-
-Note that the $year element is I<not> simply the last two digits of
-the year. If you assume it is then you create non-Y2K-compliant
-programs--and you wouldn't want to do that, would you?
-
-The proper way to get a complete 4-digit year is simply:
-
- $year += 1900;
-
-And to get the last two digits of the year (e.g., '01' in 2001) do:
-
- $year = sprintf("%02d", $year % 100);
-
-If EXPR is omitted, C<gmtime()> uses the current time (C<gmtime(time)>).
-
-In scalar context, C<gmtime()> returns the ctime(3) value:
-
- $now_string = gmtime; # e.g., "Thu Oct 13 04:54:34 1994"
+Works just like L<localtime> but the returned values are
+localized for the standard Greenwich time zone.
-If you need local time instead of GMT use the L</localtime> builtin.
-See also the C<timegm> function provided by the C<Time::Local> module,
-and the strftime(3) and mktime(3) functions available via the L<POSIX> module.
-
-This scalar value is B<not> locale dependent (see L<perllocale>), but is
-instead a Perl builtin. To get somewhat similar but locale dependent date
-strings, see the example in L</localtime>.
+Note: when called in list context, $isdst, the last value
+returned by gmtime is always C<0>. There is no
+Daylight Saving Time in GMT.
See L<perlport/gmtime> for portability concerns.
is not found, C<index> returns one less than the base, ordinarily C<-1>.
=item int EXPR
-X<int> X<integer> X<truncate> X<trunc>
+X<int> X<integer> X<truncate> X<trunc> X<floor>
=item int
$cnt = kill 1, $child1, $child2;
kill 9, @goners;
-If SIGNAL is zero, no signal is sent to the process. This is a
-useful way to check that a child process is alive and hasn't changed
-its UID. See L<perlport> for notes on the portability of this
-construct.
+If SIGNAL is zero, no signal is sent to the process, but the kill(2)
+system call will check whether it's possible to send a signal to it (that
+means, to be brief, that the process is owned by the same user, or we are
+the super-user). This is a useful way to check that a child process is
+alive (even if only as a zombie) and hasn't changed its UID. See
+L<perlport> for notes on the portability of this construct.
Unlike in the shell, if SIGNAL is negative, it kills
process groups instead of processes. (On System V, a negative I<PROCESS>
Note the I<characters>: if the EXPR is in Unicode, you will get the
number of characters, not the number of bytes. To get the length
-in bytes, use C<do { use bytes; length(EXPR) }>, see L<bytes>.
+of the internal string in bytes, use C<bytes::length(EXPR)>, see
+L<bytes>. Note that the internal encoding is variable, and the number
+of bytes usually meaningless. To get the number of bytes that the
+string would have when encoded as UTF-8, use
+C<length(Encoding::encode_utf8(EXPR))>.
=item link OLDFILE,NEWFILE
X<link>
for details, including issues with tied arrays and hashes.
=item localtime EXPR
-X<localtime>
+X<localtime> X<ctime>
=item localtime
$year += 1900;
+Otherwise you create non-Y2K-compliant programs--and you wouldn't want
+to do that, would you?
+
To get the last two digits of the year (e.g., '01' in 2001) do:
$year = sprintf("%02d", $year % 100);
See L<perlport/localtime> for portability concerns.
+The L<Time::gmtime> and L<Time::localtime> modules provides a convenient,
+by-name access mechanism to the gmtime() and localtime() functions,
+respectively.
+
+For a comprehensive date and time representation look at the
+L<DateTime> module on CPAN.
+
=item lock THING
X<lock>
translates a list of numbers to the corresponding characters. And
- %hash = map { getkey($_) => $_ } @array;
+ %hash = map { get_a_key_for($_) => $_ } @array;
is just a funny way to write
%hash = ();
- foreach $_ (@array) {
- $hash{getkey($_)} = $_;
+ foreach (@array) {
+ $hash{get_a_key_for($_)} = $_;
}
Note that C<$_> is an alias to the list value, so it can be used to
the original list for which the BLOCK or EXPR evaluates to true.
If C<$_> is lexical in the scope where the C<map> appears (because it has
-been declared with C<my $_>) then, in addition to being locally aliased to
-the list elements, C<$_> keeps being lexical inside the block; i.e. it
+been declared with C<my $_>), then, in addition to being locally aliased to
+the list elements, C<$_> keeps being lexical inside the block; that is, it
can't be seen from the outside, avoiding any potential side-effects.
C<{> starts both hash references and blocks, so C<map { ...> could be either
%hash = map ( lc($_), 1 ), @array # evaluates to (1, @array)
-or to force an anon hash constructor use C<+{>
+or to force an anon hash constructor use C<+{>:
@hashes = map +{ lc($_), 1 }, @array # EXPR, so needs , at end
this right, so Perl automatically removes all trailing slashes to keep
everyone happy.
+In order to recursively create a directory structure look at
+the C<mkpath> function of the L<File::Path> module.
+
=item msgctl ID,CMD,ARG
X<msgctl>
=item no Module
+=item no VERSION
+
See the C<use> function, of which C<no> is the opposite.
=item oct EXPR
that affect how the input and output are processed (see L<open> and
L<PerlIO> for more details). For example
- open(FH, "<:utf8", "file")
+ open(FH, "<:encoding(UTF-8)", "file")
will open the UTF-8 encoded file containing Unicode characters,
see L<perluniintro>. Note that if layers are specified in the
uses C<$_>.
For the reverse, see L</chr>.
-See L<perlunicode> and L<encoding> for more about Unicode.
+See L<perlunicode> for more about Unicode.
=item our EXPR
X<our> X<global>
-=item our EXPR TYPE
+=item our TYPE EXPR
=item our EXPR : ATTRS
L<perlsub/"Private Variables via my()"> for details, and L<fields>,
L<attributes>, and L<Attribute::Handlers>.
-The only currently recognized C<our()> attribute is C<unique> which
-indicates that a single copy of the global is to be used by all
-interpreters should the program happen to be running in a
-multi-interpreter environment. (The default behaviour would be for
-each interpreter to have its own copy of the global.) Examples:
-
- our @EXPORT : unique = qw(foo);
- our %EXPORT_TAGS : unique = (bar => [qw(aa bb cc)]);
- our $VERSION : unique = "1.00";
-
-Note that this attribute also has the effect of making the global
-readonly when the first new interpreter is cloned (for example,
-when the first new thread is created).
-
-Multi-interpreter environments can come to being either through the
-fork() emulation on Windows platforms, or by embedding perl in a
-multi-threaded application. The C<unique> attribute does nothing in
-all other environments.
-
-Warning: the current implementation of this attribute operates on the
-typeglob associated with the variable; this means that C<our $x : unique>
-also has the effect of C<our @x : unique; our %x : unique>. This may be
-subject to change.
-
=item pack TEMPLATE,LIST
X<pack>
I A unsigned integer value.
(This 'integer' is _at_least_ 32 bits wide. Its exact
size depends on what a local C compiler calls 'int'.)
-
+
n An unsigned short (16-bit) in "network" (big-endian) order.
N An unsigned long (32-bit) in "network" (big-endian) order.
v An unsigned short (16-bit) in "VAX" (little-endian) order.
The C</> template character allows packing and unpacking of a sequence of
items where the packed structure contains a packed item count followed by
the packed items themselves.
-You write I<length-item>C</>I<sequence-item>.
-The I<length-item> can be any C<pack> template letter, and describes
-how the length value is packed. The ones likely to be of most use are
-integer-packing ones like C<n> (for Java strings), C<w> (for ASN.1 or
-SNMP) and C<N> (for Sun XDR).
+For C<pack> you write I<length-item>C</>I<sequence-item> and the
+I<length-item> describes how the length value is packed. The ones likely
+to be of most use are integer-packing ones like C<n> (for Java strings),
+C<w> (for ASN.1 or SNMP) and C<N> (for Sun XDR).
For C<pack>, the I<sequence-item> may have a repeat count, in which case
the minimum of that and the number of available items is used as argument
for the I<length-item>. If it has no repeat count or uses a '*', the number
-of available items is used. For C<unpack> the repeat count is always obtained
-by decoding the packed item count, and the I<sequence-item> must not have a
-repeat count.
+of available items is used.
+
+For C<unpack> an internal stack of integer arguments unpacked so far is
+used. You write C</>I<sequence-item> and the repeat count is obtained by
+popping off the last element from the stack. The I<sequence-item> must not
+have a repeat count.
If the I<sequence-item> refers to a string type (C<"A">, C<"a"> or C<"Z">),
the I<length-item> is a string length, not a number of strings. If there is
an explicit repeat count for pack, the packed string will be adjusted to that
given length.
- unpack 'W/a', "\04Gurusamy"; gives ('Guru')
- unpack 'a3/A* A*', '007 Bond J '; gives (' Bond', 'J')
- pack 'n/a* w/a','hello,','world'; gives "\000\006hello,\005world"
- pack 'a/W2', ord('a') .. ord('z'); gives '2ab'
+ unpack 'W/a', "\04Gurusamy"; gives ('Guru')
+ unpack 'a3/A A*', '007 Bond J '; gives (' Bond', 'J')
+ unpack 'a3 x2 /A A*', '007: Bond, J.'; gives ('Bond, J', '.')
+ pack 'n/a* w/a','hello,','world'; gives "\000\006hello,\005world"
+ pack 'a/W2', ord('a') .. ord('z'); gives '2ab'
The I<length-item> is not returned explicitly from C<unpack>.
Equivalent to C<print FILEHANDLE sprintf(FORMAT, LIST)>, except that C<$\>
(the output record separator) is not appended. The first argument
of the list will be interpreted as the C<printf> format. See C<sprintf>
-for an explanation of the format argument. If C<use locale> is in effect,
-the character used for the decimal point in formatted real numbers is
-affected by the LC_NUMERIC locale. See L<perllocale>.
+for an explanation of the format argument. If C<use locale> is in effect,
+and POSIX::setlocale() has been called, the character used for the decimal
+separator in formatted floating point numbers is affected by the LC_NUMERIC
+locale. See L<perllocale> and L<POSIX>.
Don't fall into the trap of using a C<printf> when a simple
C<print> would do. The C<print> is more efficient and less
prototype is returned.
=item push ARRAY,LIST
-X<push>, X<stack>
+X<push> X<stack>
Treats ARRAY as a stack, and pushes the values of LIST
onto the end of ARRAY. The length of ARRAY increases by the length of
with the wrong number of RANDBITS.)
=item read FILEHANDLE,SCALAR,LENGTH,OFFSET
-X<read>
+X<read> X<file, read>
=item read FILEHANDLE,SCALAR,LENGTH
closedir DIR;
=item readline EXPR
+
+=item readline
X<readline> X<gets> X<fgets>
-Reads from the filehandle whose typeglob is contained in EXPR. 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 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/"$/">.
+Reads from the filehandle whose typeglob is contained in EXPR (or from
+*ARGV if EXPR is not provided). In scalar context, each call reads and
+returns the next line, until end-of-file is reached, whereupon the
+subsequent call returns undef. In list context, reads until end-of-file
+is reached and returns a list of lines. Note that the notion of "line"
+used here is however you may have defined it with C<$/> or
+C<$INPUT_RECORD_SEPARATOR>). See L<perlvar/"$/">.
When C<$/> is set to C<undef>, when readline() is in scalar
context (i.e. file slurp mode), and when an empty file is read, it
omitted, uses C<$_>.
=item readpipe EXPR
+
+=item readpipe
X<readpipe>
EXPR is executed as a system command.
This is the internal function implementing the C<qx/EXPR/>
operator, but you can use it directly. The C<qx/EXPR/>
operator is discussed in more detail in L<perlop/"I/O Operators">.
+If EXPR is omitted, uses C<$_>.
=item recv SOCKET,SCALAR,LENGTH,FLAGS
X<recv>
REF
GLOB
LVALUE
+ FORMAT
+ IO
+ VSTRING
+ Regexp
If the referenced object has been blessed into a package, then that package
name is returned instead. You can think of C<ref> as a C<typeof> operator.
print "r is not a reference at all.\n";
}
+The return value C<LVALUE> indicates a reference to an lvalue that is not
+a variable. You get this from taking the reference of function calls like
+C<pos()> or C<substr()>. C<VSTRING> is returned if the reference points
+to a L<version string|perldata\"Version Strings">.
+
+The result C<Regexp> indicates that the argument is a regular expression
+resulting from C<qr//>.
+
See also L<perlref>.
=item rename OLDNAME,NEWNAME
open files, or pre-existing files. Check L<perlport> and either the
rename(2) manpage or equivalent system documentation for details.
+For a platform independent C<move> function look at the L<File::Copy>
+module.
+
=item require VERSION
X<require>
Otherwise, C<require> demands that a library file be included if it
hasn't already been included. The file is included via the do-FILE
-mechanism, which is essentially just a variety of C<eval>. Has
-semantics similar to the following subroutine:
+mechanism, which is essentially just a variety of C<eval> with the
+caveat that lexical variables in the invoking script will be invisible
+to the included code. Has semantics similar to the following subroutine:
sub require {
my ($filename) = @_;
eval "require $class";
-Now that you understand how C<require> looks for files in the case of
-a bareword argument, there is a little extra functionality going on
-behind the scenes. Before C<require> looks for a "F<.pm>" extension,
-it will first look for a filename with a "F<.pmc>" extension. A file
-with this extension is assumed to be Perl bytecode generated by
-L<B::Bytecode|B::Bytecode>. If this file is found, and its modification
-time is newer than a coinciding "F<.pm>" non-compiled file, it will be
-loaded in place of that non-compiled file ending in a "F<.pm>" extension.
+Now that you understand how C<require> looks for files in the case of a
+bareword argument, there is a little extra functionality going on behind
+the scenes. Before C<require> looks for a "F<.pm>" extension, it will
+first look for a similar filename with a "F<.pmc>" extension. If this file
+is found, it will be loaded in place of any file ending in a "F<.pm>"
+extension.
You can also insert hooks into the import facility, by putting directly
Perl code into the @INC array. There are three forms of hooks: subroutine
walks through @INC and encounters a subroutine, this subroutine gets
called with two parameters, the first being a reference to itself, and the
second the name of the file to be included (e.g. "F<Foo/Bar.pm>"). The
-subroutine should return C<undef> or a filehandle, from which the file to
-include will be read. If C<undef> is returned, C<require> will look at
-the remaining elements of @INC.
+subroutine should return nothing, or a list of up to three values in the
+following order:
+
+=over
+
+=item 1
+
+A filehandle, from which the file will be read.
+
+=item 2
+
+A reference to a subroutine. If there is no filehandle (previous item),
+then this subroutine is expected to generate one line of source code per
+call, writing the line into C<$_> and returning 1, then returning 0 at
+"end of file". If there is a filehandle, then the subroutine will be
+called to act a simple source filter, with the line as read in C<$_>.
+Again, return 1 for each valid line, and 0 after all lines have been
+returned.
+
+=item 3
+
+Optional state for the subroutine. The state is passed in as C<$_[1]>. A
+reference to the subroutine itself is passed in as C<$_[0]>.
+
+=back
+
+If an empty list, C<undef>, or nothing that matches the first 3 values above
+is returned then C<require> will look at the remaining elements of @INC.
+Note that this file handle must be a real file handle (strictly a typeglob,
+or reference to a typeglob, blessed or unblessed) - tied file handles will be
+ignored and return value processing will stop there.
If the hook is an array reference, its first element must be a subroutine
reference. This subroutine is called as above, but the first parameter is
If the hook is an object, it must provide an INC method that will be
called as above, the first parameter being the object itself. (Note that
-you must fully qualify the sub's name, as it is always forced into package
-C<main>.) Here is a typical code layout:
+you must fully qualify the sub's name, as unqualified C<INC> is always forced
+into package C<main>.) Here is a typical code layout:
# In Foo.pm
package Foo;
empty. If it succeeds it returns true, otherwise it returns false and
sets C<$!> (errno). If FILENAME is omitted, uses C<$_>.
+To remove a directory tree recursively (C<rm -rf> on unix) look at
+the C<rmtree> function of the L<File::Path> module.
+
=item s///
The substitution operator. See L<perlop>.
=item say
Just like C<print>, but implicitly appends a newline.
-C<say LIST> is simply an abbreviation for C<print LIST, "\n">,
-and C<say()> works just like C<print($_, "\n")>.
-
-That means that a call to say() appends any output record separator
-I<after> the added newline.
+C<say LIST> is simply an abbreviation for C<{ local $\ = "\n"; print
+LIST }>.
This keyword is only available when the "say" feature is
enabled: see L<feature>.
=item select
-Returns the currently selected filehandle. Sets the current default
-filehandle for output, if FILEHANDLE is supplied. This has two
+Returns the currently selected filehandle. If FILEHANDLE is supplied,
+sets the new current default filehandle for output. This has two
effects: first, a C<write> or a C<print> without a filehandle will
default to this FILEHANDLE. Second, references to variables related to
output will refer to this output channel. For example, if you have to
array, returns the undefined value. If ARRAY is omitted, shifts the
C<@_> array within the lexical scope of subroutines and formats, and the
C<@ARGV> array outside of a subroutine and also within the lexical scopes
-established by the C<eval STRING>, C<BEGIN {}>, C<INIT {}>, C<CHECK {}>
-and C<END {}> constructs.
+established by the C<eval STRING>, C<BEGIN {}>, C<INIT {}>, C<CHECK {}>,
+C<UNITCHECK {}> and C<END {}> constructs.
See also C<unshift>, C<push>, and C<pop>. C<shift> and C<unshift> do the
same thing to the left end of an array that C<pop> and C<push> do to the
%E like %e, but using an upper-case "E"
%G like %g, but with an upper-case "E" (if applicable)
%b an unsigned integer, in binary
+ %B like %b, but using an upper-case "B" with the # flag
%p a pointer (outputs the Perl value's address in hexadecimal)
%n special: *stores* the number of characters output so far
into the next variable in the parameter list
=item flags
one or more of:
+
space prefix positive number with a space
+ prefix positive number with a plus sign
- left-justify within the field
0 use zeros, not spaces, to right-justify
- # prefix non-zero octal with "0", non-zero hex with "0x",
- non-zero binary with "0b"
+ # ensure the leading "0" for any octal,
+ prefix non-zero hexadecimal with "0x" or "0X",
+ prefix non-zero binary with "0b" or "0B"
For example:
- printf '<% d>', 12; # prints "< 12>"
- printf '<%+d>', 12; # prints "<+12>"
- printf '<%6s>', 12; # prints "< 12>"
- printf '<%-6s>', 12; # prints "<12 >"
- printf '<%06s>', 12; # prints "<000012>"
- printf '<%#x>', 12; # prints "<0xc>"
+ printf '<% d>', 12; # prints "< 12>"
+ printf '<%+d>', 12; # prints "<+12>"
+ printf '<%6s>', 12; # prints "< 12>"
+ printf '<%-6s>', 12; # prints "<12 >"
+ printf '<%06s>', 12; # prints "<000012>"
+ printf '<%#o>', 12; # prints "<014>"
+ printf '<%#x>', 12; # prints "<0xc>"
+ printf '<%#X>', 12; # prints "<0XC>"
+ printf '<%#b>', 12; # prints "<0b1100>"
+ printf '<%#B>', 12; # prints "<0B1100>"
+
+When a space and a plus sign are given as the flags at once,
+a plus sign is used to prefix a positive number.
+
+ printf '<%+ d>', 12; # prints "<+12>"
+ printf '<% +d>', 12; # prints "<+12>"
+
+When the # flag and a precision are given in the %o conversion,
+the precision is incremented if it's necessary for the leading "0".
+
+ printf '<%#.5o>', 012; # prints "<00012>"
+ printf '<%#.5o>', 012345; # prints "<012345>"
+ printf '<%#.0o>', 0; # prints "<0>"
=item vector flag
printf '<%.4g>', 100.01; # prints "<100>"
For integer conversions, specifying a precision implies that the
-output of the number itself should be zero-padded to this width:
+output of the number itself should be zero-padded to this width,
+where the 0 flag is ignored:
+
+ printf '<%.6d>', 1; # prints "<000001>"
+ printf '<%+.6d>', 1; # prints "<+000001>"
+ printf '<%-10.6d>', 1; # prints "<000001 >"
+ printf '<%10.6d>', 1; # prints "< 000001>"
+ printf '<%010.6d>', 1; # prints "< 000001>"
+ printf '<%+10.6d>', 1; # prints "< +000001>"
printf '<%.6x>', 1; # prints "<000001>"
printf '<%#.6x>', 1; # prints "<0x000001>"
printf '<%-10.6x>', 1; # prints "<000001 >"
+ printf '<%10.6x>', 1; # prints "< 000001>"
+ printf '<%010.6x>', 1; # prints "< 000001>"
+ printf '<%#10.6x>', 1; # prints "< 0x000001>"
For string conversions, specifying a precision truncates the string
to fit in the specified width:
printf '<%.6x>', 1; # prints "<000001>"
printf '<%.*x>', 6, 1; # prints "<000001>"
+If a precision obtained through C<*> is negative, it has the same
+effect as no precision.
+
+ printf '<%.*s>', 7, "string"; # prints "<string>"
+ printf '<%.*s>', 3, "string"; # prints "<str>"
+ printf '<%.*s>', 0, "string"; # prints "<>"
+ printf '<%.*s>', -1, "string"; # prints "<string>"
+
+ printf '<%.*d>', 1, 0; # prints "<0>"
+ printf '<%.*d>', 0, 0; # prints "<>"
+ printf '<%.*d>', -1, 0; # prints "<0>"
+
You cannot currently get the precision from a specified number,
but it is intended that this will be possible in the future using
e.g. C<.*2$>:
=back
-If C<use locale> is in effect, the character used for the decimal
-point in formatted real numbers is affected by the LC_NUMERIC locale.
-See L<perllocale>.
+If C<use locale> is in effect, and POSIX::setlocale() has been called,
+the character used for the decimal separator in formatted floating
+point numbers is affected by the LC_NUMERIC locale. See L<perllocale>
+and L<POSIX>.
=item sqrt EXPR
X<sqrt> X<root> X<square root>
one-third of the time. So don't do that.
=item stat FILEHANDLE
-X<stat> X<file, status>
+X<stat> X<file, status> X<ctime>
=item stat EXPR
+=item stat DIRHANDLE
+
=item stat
Returns a 13-element list giving the status info for a file, either
-the file opened via FILEHANDLE, or named by EXPR. If EXPR is omitted,
-it stats C<$_>. Returns a null list if the stat fails. Typically used
-as follows:
+the file opened via FILEHANDLE or DIRHANDLE, or named by EXPR. If EXPR is
+omitted, it stats C<$_>. Returns a null list if the stat fails. Typically
+used as follows:
($dev,$ino,$mode,$nlink,$uid,$gid,$rdev,$size,
$atime,$mtime,$ctime,$blksize,$blocks)
or failure, and, if successful, sets the information associated with
the special filehandle C<_>.
-The File::stat module provides a convenient, by-name access mechanism:
+The L<File::stat> module provides a convenient, by-name access mechanism:
use File::stat;
$sb = stat($filename);
printf "Permissions are %04o\n", S_IMODE($mode), "\n";
$is_setuid = $mode & S_ISUID;
- $is_setgid = S_ISDIR($mode);
+ $is_directory = S_ISDIR($mode);
You could write the last two using the C<-u> and C<-d> operators.
The commonly available C<S_IF*> constants are
# File types. Not necessarily all are available on your system.
- S_IFREG S_IFDIR S_IFLNK S_IFBLK S_ISCHR S_IFIFO S_IFSOCK S_IFWHT S_ENFMT
+ S_IFREG S_IFDIR S_IFLNK S_IFBLK S_IFCHR S_IFIFO S_IFSOCK S_IFWHT S_ENFMT
# The following are compatibility aliases for S_IRUSR, S_IWUSR, S_IXUSR.
about the C<S_*> constants. To get status info for a symbolic link
instead of the target file behind the link, use the C<lstat> function.
+=item state EXPR
+X<state>
+
+=item state TYPE EXPR
+
+=item state EXPR : ATTRS
+
+=item state TYPE EXPR : ATTRS
+
+C<state> declares a lexically scoped variable, just like C<my> does.
+However, those variables will be initialized only once, contrary to
+lexical variables that are reinitialized each time their enclosing block
+is entered.
+
+C<state> variables are only enabled when the C<feature 'state'> pragma is
+in effect. See L<feature>.
+
=item study SCALAR
X<study>
everything to the end of the string. If LENGTH is negative, leaves that
many characters off the end of the string.
+ my $s = "The black cat climbed the green tree";
+ my $color = substr $s, 4, 5; # black
+ my $middle = substr $s, 4, -11; # black cat climbed the
+ my $end = substr $s, 14; # climbed the green tree
+ my $tail = substr $s, -4; # tree
+ my $z = substr $s, -4, 2; # tr
+
You can use the substr() function as an lvalue, in which case EXPR
must itself be an lvalue. If you assign something shorter than LENGTH,
the string will shrink, and if you assign something longer than LENGTH,
parts of the EXPR and return what was there before in one operation,
just as you can with splice().
+ my $s = "The black cat climbed the green tree";
+ my $z = substr $s, 14, 7, "jumped from"; # climbed
+ # $s is now "The black cat jumped from the green tree"
+
Note that the lvalue returned by the 3-arg version of substr() acts as
a 'magic bullet'; each time it is assigned to, it remembers which part
of the original string is being modified; for example:
$_ = 'pq'; print $x,"\n"; # prints 5pq9
}
-
Prior to Perl version 5.9.1, the result of using an lvalue multiple times was
unspecified.
1904 in the current local time zone for its epoch.
For measuring time in better granularity than one second,
-you may use either the Time::HiRes module (from CPAN, and starting from
+you may use either the L<Time::HiRes> module (from CPAN, and starting from
Perl 5.8 part of the standard distribution), or if you have
gettimeofday(2), you may be able to use the C<syscall> interface of Perl.
See L<perlfaq8> for details.
+For date and time processing look at the many related modules on CPAN.
+For a comprehensive date and time representation look at the
+L<DateTime> module.
+
=item times
X<times>
In scalar context, C<times> returns C<$user>.
+Note that times for children are included only after they terminate.
+
=item tr///
The transliteration operator. Same as C<y///>. See L<perlop>.
The behavior is undefined if LENGTH is greater than the length of the
file.
+The position in the file of FILEHANDLE is left unchanged. You may want to
+call L<seek> before writing to the file.
+
=item uc EXPR
X<uc> X<uppercase> X<toupper>
Note that this is a unary operator, not a list operator.
=item unlink LIST
-X<unlink> X<delete> X<remove> X<rm>
+X<unlink> X<delete> X<remove> X<rm> X<del>
=item unlink
except that Module I<must> be a bareword.
-VERSION may be either a numeric argument such as 5.006, which will be
-compared to C<$]>, or a literal of the form v5.6.1, which will be compared
-to C<$^V> (aka $PERL_VERSION. A fatal error is produced if VERSION is
-greater than the version of the current Perl interpreter; Perl will not
-attempt to parse the rest of the file. Compare with L</require>, which can
-do a similar check at run time.
+In the peculiar C<use VERSION> form, VERSION may be either a numeric
+argument such as 5.006, which will be compared to C<$]>, or a literal of
+the form v5.6.1, which will be compared to C<$^V> (aka $PERL_VERSION). A
+fatal error is produced if VERSION is greater than the version of the
+current Perl interpreter; Perl will not attempt to parse the rest of the
+file. Compare with L</require>, which can do a similar check at run time.
+Symmetrically, C<no VERSION> allows you to specify that you want a version
+of perl older than the specified one.
Specifying VERSION as a literal of the form v5.6.1 should generally be
avoided, because it leads to misleading error messages under earlier
C<use>ing library modules that have changed in incompatible ways from
older versions of Perl. (We try not to do this more than we have to.)
+Also, if the specified perl version is greater than or equal to 5.9.5,
+C<use VERSION> will also load the C<feature> pragma and enable all
+features available in the requested version. See L<feature>.
+
The C<BEGIN> forces the C<require> and C<import> to happen at compile time. The
C<require> makes sure the module is loaded into memory if it hasn't been
yet. The C<import> is not a builtin--it's just an ordinary static method
On systems that support futimes, you might pass file handles among the
files. On systems that don't support futimes, passing file handles
-produces a fatal error at run time.
+produces a fatal error at run time. The file handles must be passed
+as globs or references to be recognized. Barewords are considered
+file names.
=item values HASH
X<values>
extend the string with sufficiently many zero bytes. It is an error
to try to write off the beginning of the string (i.e. negative OFFSET).
-The string should not contain any character with the value > 255 (which
-can only happen if you're using UTF-8 encoding). If it does, it will be
-treated as something that is not UTF-8 encoded. When the C<vec> was
-assigned to, other parts of your program will also no longer consider the
-string to be UTF-8 encoded. In other words, if you do have such characters
-in your string, vec() will operate on the actual byte string, and not the
-conceptual character string.
+If the string happens to be encoded as UTF-8 internally (and thus has
+the UTF8 flag set), this is ignored by C<vec>, and it operates on the
+internal byte string, not the conceptual character string, even if you
+only have characters with values less than 256.
Strings created with C<vec> can also be manipulated with the logical
operators C<|>, C<&>, C<^>, and C<~>. These operators will assume a bit
#...
do {
$kid = waitpid(-1, WNOHANG);
- } until $kid > 0;
+ } while $kid > 0;
then you can do a non-blocking wait for all pending zombie processes.
Non-blocking wait is available on machines supporting either the
return wantarray ? @a : "@a";
C<wantarray()>'s result is unspecified in the top level of a file,
-in a C<BEGIN>, C<CHECK>, C<INIT> or C<END> block, or in a C<DESTROY>
-method.
+in a C<BEGIN>, C<UNITCHECK>, C<CHECK>, C<INIT> or C<END> block, or
+in a C<DESTROY> method.
This function should have been named wantlist() instead.
=item warn LIST
X<warn> X<warning> X<STDERR>
-Produces a message on STDERR just like C<die>, but doesn't exit or throw
-an exception.
+Prints the value of LIST to STDERR. If the last element of LIST does
+not end in a newline, appends the same text as C<die> does.
If LIST is empty and C<$@> already contains a value (typically from a
previous eval) that value is used after appending C<"\t...caught">
https://perl5.git.perl.org / perl5.git / blobdiff