X-Git-Url: http://git.shadowcat.co.uk/gitweb/gitweb.cgi?a=blobdiff_plain;f=pod%2Fperlfunc.pod;h=8722105c2b6fa9beffc50b5e9ca9b9b71f1f974a;hb=1b1f1335be81080356b687a63b64fde210a3b697;hp=0d620d90dc9fc95fbd397b580130faa24888ca3c;hpb=847a5fae45dac396d0f9e1bb61d5b4ff9d94cdcd;p=p5sagit%2Fp5-mst-13.2.git diff --git a/pod/perlfunc.pod b/pod/perlfunc.pod index 0d620d9..8722105 100644 --- a/pod/perlfunc.pod +++ b/pod/perlfunc.pod @@ -96,9 +96,8 @@ than one place. =item Functions for SCALARs or strings C, C, C, C, C, C, C, C, -C, C, C, C, C, C, C, -C, C, C, C, C, C, C, -C +C, C, C, C, C, C, C, +C, C, C, C, C, C, C =item Regular expressions and pattern matching @@ -173,7 +172,7 @@ C, C C, C, C, C, C, C, C, C, C, C, C, -C, C +C, C, C =item System V interprocess communication functions @@ -201,7 +200,7 @@ C, C, C.) If EXPR is omitted, uses C<$_>. print hex 'aF'; # same Hex strings may only represent integers. Strings that would cause -integer overflow trigger a warning. +integer overflow trigger a warning. Leading whitespace is not stripped, +unlike oct(). =item import There is no builtin C function. It is just an ordinary method (subroutine) defined (or inherited) by modules that wish to export names to another module. The C function calls the C method -for the package used. See also L, L, and L. +for the package used. See also L, L, and L. =item index STR,SUBSTR,POSITION @@ -2175,7 +2186,7 @@ has no string value but does have a numeric value, that value will be passed rather than a pointer to the string value. To guarantee this to be true, add a C<0> to the scalar before using it.) The C and C functions may be needed to manipulate the values of structures used by -C. +C. The return value of C (and C) is as follows: @@ -2230,7 +2241,7 @@ Here is yet another way to print your environment: @keys = keys %ENV; @values = values %ENV; - while (@keys) { + while (@keys) { print pop(@keys), '=', pop(@values), "\n"; } @@ -2317,9 +2328,9 @@ C work. =item lc Returns an lowercased version of EXPR. This is the internal function -implementing the C<\L> escape in double-quoted strings. -Respects current LC_CTYPE locale if C in force. See L -and L. +implementing the C<\L> escape in double-quoted strings. Respects +current LC_CTYPE locale if C in force. See L +and L for more details about locale and Unicode support. If EXPR is omitted, uses C<$_>. @@ -2327,9 +2338,11 @@ If EXPR is omitted, uses C<$_>. =item lcfirst -Returns the value of EXPR with the first character lowercased. This is -the internal function implementing the C<\l> escape in double-quoted strings. -Respects current LC_CTYPE locale if C in force. See L. +Returns the value of EXPR with the first character lowercased. This +is the internal function implementing the C<\l> escape in +double-quoted strings. Respects current LC_CTYPE locale if C in force. See L and L for more +details about locale and Unicode support. If EXPR is omitted, uses C<$_>. @@ -2338,24 +2351,25 @@ If EXPR is omitted, uses C<$_>. =item length Returns the length in characters of the value of EXPR. If EXPR is -omitted, returns length of C<$_>. Note that this cannot be used on +omitted, returns length of C<$_>. Note that this cannot be used on an entire array or hash to find out how many elements these have. For that, use C and C respectively. =item link OLDFILE,NEWFILE Creates a new filename linked to the old filename. Returns true for -success, false otherwise. +success, false otherwise. =item listen SOCKET,QUEUESIZE Does the same thing that the listen system call does. Returns true if -it succeeded, false otherwise. See the example in L. +it succeeded, false otherwise. See the example in +L. =item local EXPR You really probably want to be using C instead, because C isn't -what most people think of as "local". See +what most people think of as "local". See L for details. A local modifies the listed variables to be local to the enclosing @@ -2440,7 +2454,7 @@ divided by the natural log of N. For example: sub log10 { my $n = shift; return log($n)/log(10); - } + } See also L for the inverse operation. @@ -2504,7 +2518,7 @@ such as using a unary C<+> to give perl some help: %hash = map { ("\L$_", 1) } @array # this also works %hash = map { lc($_), 1 } @array # as does this. %hash = map +( lc($_), 1 ), @array # this is EXPR and works! - + %hash = map ( lc($_), 1 ), @array # evaluates to (1, @array) or to force an anon hash constructor use C<+{> @@ -2619,8 +2633,9 @@ See the L function, which C is the opposite of. Interprets EXPR as an octal string and returns the corresponding value. (If EXPR happens to start off with C<0x>, interprets it as a hex string. If EXPR starts off with C<0b>, it is interpreted as a -binary string.) The following will handle decimal, binary, octal, and -hex in the standard Perl or C notation: +binary string. Leading whitespace is ignored in all three cases.) +The following will handle decimal, binary, octal, and hex in the standard +Perl or C notation: $val = oct($val) if $val =~ /^0/; @@ -2635,15 +2650,18 @@ to be converted into a file mode, for example. (Although perl will automatically convert strings into numbers as needed, this automatic conversion assumes base 10.) -=item open FILEHANDLE,MODE,LIST - =item open FILEHANDLE,EXPR +=item open FILEHANDLE,MODE,EXPR + +=item open FILEHANDLE,MODE,EXPR,LIST + =item open FILEHANDLE Opens the file whose filename is given by EXPR, and associates it with -FILEHANDLE. If FILEHANDLE is an expression, its value is used as the -name of the real filehandle wanted. (This is considered a symbolic +FILEHANDLE. If FILEHANDLE is an undefined lexical (C) variable the variable is +assigned a reference to a new anonymous filehandle, otherwise if FILEHANDLE is an expression, +its value is used as the name of the real filehandle wanted. (This is considered a symbolic reference, so C should I be in effect.) If EXPR is omitted, the scalar @@ -2653,10 +2671,11 @@ for this purpose; so if you're using C, specify EXPR in your call to open.) See L for a kinder, gentler explanation of opening files. -If MODE is C<< '<' >> or nothing, the file is opened for input. +If three or more arguments are specified then the mode of opening and the file name +are separate. If MODE is C<< '<' >> or nothing, the file is opened for input. If MODE is C<< '>' >>, the file is truncated and opened for output, being created if necessary. If MODE is C<<< '>>' >>>, -the file is opened for appending, again being created if necessary. +the file is opened for appending, again being created if necessary. You can put a C<'+'> in front of the C<< '>' >> or C<< '<' >> to indicate that you want both read and write access to the file; thus C<< '+<' >> is almost always preferred for read/write updates--the C<< '+>' >> mode would clobber the @@ -2670,7 +2689,8 @@ C<'w'>, C<'w+'>, C<'a'>, and C<'a+'>. In the 2-arguments (and 1-argument) form of the call the mode and filename should be concatenated (in this order), possibly separated by -spaces. It is possible to omit the mode if the mode is C<< '<' >>. +spaces. It is possible to omit the mode in these forms if the mode is +C<< '<' >>. If the filename begins with C<'|'>, the filename is interpreted as a command to which output is to be piped, and if the filename ends with a @@ -2681,17 +2701,21 @@ that pipes both in I out, but see L, L, and L for alternatives.) -If MODE is C<'|-'>, the filename is interpreted as a +For three or more arguments if MODE is C<'|-'>, the filename is interpreted as a command to which output is to be piped, and if MODE is C<'-|'>, the filename is interpreted as a command which pipes output to us. In the 2-arguments (and 1-argument) form one should replace dash (C<'-'>) with the command. See L for more examples of this. (You are not allowed to C to a command that pipes both in I out, but see L, L, -and L for alternatives.) +and L for alternatives.) In 3+ arg form of +pipe opens then if LIST is specified (extra arguments after the command name) then +LIST becomes arguments to the command invoked if the platform supports it. +The meaning of C with more than three arguments for non-pipe modes +is not yet specified. Experimental "layers" may give extra LIST arguments meaning. In the 2-arguments (and 1-argument) form opening C<'-'> opens STDIN -and opening C<< '>-' >> opens STDOUT. +and opening C<< '>-' >> opens STDOUT. Open returns nonzero upon success, the undefined value otherwise. If the C @@ -2706,6 +2730,10 @@ and those that don't is their text file formats. Systems like Unix, MacOS, and Plan9, which delimit lines with a single character, and which encode that character in C as C<"\n">, do not need C. The rest need it. +In the three argument form MODE may also contain a list of IO "layers" (see L and +L for more details) to be applied to the handle. This can be used to achieve the +effect of C as well as more complex behaviours. + When opening a file, it's usually a bad idea to continue normal execution if the request failed, so C is frequently used in connection with C. Even if C won't do what you want (say, in a CGI script, @@ -2714,6 +2742,14 @@ modules that can help with that problem)) you should always check the return value from opening a file. The infrequent exception is when working with an unopened filehandle is actually what you want to do. +As a special case the 3 arg form with a read/write mode and the third argument +being C: + + open(TMP, "+>", undef) or die ... + +opens a filehandle to an anonymous temporary file. + + Examples: $ARTICLE = 100; @@ -2769,14 +2805,14 @@ duped and opened. You may use C<&> after C<< > >>, C<<< >> >>>, C<< < >>, C<< +> >>, C<<< +>> >>>, and C<< +< >>. The mode you specify should match the mode of the original filehandle. (Duping a filehandle does not take into account any existing contents of -stdio buffers.) Duping file handles is not yet supported for 3-argument -open(). +stdio buffers.) If you use the 3 arg form then you can pass either a number, +the name of a filehandle or the normal "reference to a glob". Here is a script that saves, redirects, and restores STDOUT and STDERR: #!/usr/bin/perl - open(OLDOUT, ">&STDOUT"); + open(my $oldout, ">&", \*STDOUT); open(OLDERR, ">&STDERR"); open(STDOUT, '>', "foo.out") || die "Can't redirect stdout"; @@ -2797,17 +2833,24 @@ STDERR: print STDOUT "stdout 2\n"; print STDERR "stderr 2\n"; -If you specify C<< '<&=N' >>, where C is a number, then Perl will do an -equivalent of C's C of that file descriptor; this is more -parsimonious of file descriptors. For example: +If you specify C<< '<&=N' >>, where C is a number, then Perl will +do an equivalent of C's C of that file descriptor; this is +more parsimonious of file descriptors. For example: open(FILEHANDLE, "<&=$fd") -Note that this feature depends on the fdopen() C library function. -On many UNIX systems, fdopen() is known to fail when file descriptors +or + + open(FILEHANDLE, "<&=", $fd) + +Note that if Perl is using the standard C libraries' fdopen() then on +many UNIX systems, fdopen() is known to fail when file descriptors exceed a certain value, typically 255. If you need more file -descriptors than that, consider rebuilding Perl to use the C -library. +descriptors than that, consider rebuilding Perl to use the C. + +You can see whether Perl has been compiled with PerlIO or not by +running C and looking for C line. If C +is C, you have PerlIO, otherwise you don't. If you open a pipe on the command C<'-'>, i.e., either C<'|-'> or C<'-|'> with 2-arguments (or 1-argument) form of open(), then @@ -2826,10 +2869,15 @@ The following triples are more or less equivalent: open(FOO, "|tr '[a-z]' '[A-Z]'"); open(FOO, '|-', "tr '[a-z]' '[A-Z]'"); open(FOO, '|-') || exec 'tr', '[a-z]', '[A-Z]'; + open(FOO, '|-', "tr", '[a-z]', '[A-Z]'); open(FOO, "cat -n '$file'|"); open(FOO, '-|', "cat -n '$file'"); open(FOO, '-|') || exec 'cat', '-n', $file; + open(FOO, '-|', "cat", '-n', $file); + +The last example in each block shows the pipe as "list form", which is +not yet supported on all platforms. See L for more examples of this. @@ -2849,7 +2897,7 @@ child to finish, and returns the status value in C<$?>. The filename passed to 2-argument (or 1-argument) form of open() will have leading and trailing whitespace deleted, and the normal redirection characters -honored. This property, known as "magic open", +honored. This property, known as "magic open", can often be used to good effect. A user could specify a filename of F<"rsh cat file |">, or you could change certain filenames as needed: @@ -2922,12 +2970,17 @@ DIRHANDLEs have their own namespace separate from FILEHANDLEs. =item ord -Returns the numeric (ASCII or Unicode) value of the first character of EXPR. If -EXPR is omitted, uses C<$_>. For the reverse, see L. -See L for more about Unicode. +Returns the numeric (the native 8-bit encoding, like ASCII or EBCDIC, +or Unicode) value of the first character of EXPR. If EXPR is omitted, +uses C<$_>. + +For the reverse, see L. +See L and L for more about Unicode. =item our EXPR +=item our EXPR : ATTRIBUTES + An C declares the listed variables to be valid globals within the enclosing block, file, or C. That is, it has the same scoping rules as a "my" declaration, but does not create a local @@ -2966,6 +3019,28 @@ package, Perl will emit warnings if you have asked for them. our $bar; # emits warning +An C declaration may also have a list of attributes associated +with it. B: This is an experimental feature that may be +changed or removed in future releases of Perl. It should not be +relied upon. + +The only currently recognized attribute is C 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.) In such an environment, this +attribute also has the effect of making the global readonly. +Examples: + + our @EXPORT : unique = qw(foo); + our %EXPORT_TAGS : unique = (bar => [qw(aa bb cc)]); + our $VERSION : unique = "1.00"; + +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 attribute does nothing in +all other environments. + =item pack TEMPLATE,LIST Takes a LIST of values and converts it into a string using the rules @@ -2979,8 +3054,8 @@ sequence of characters that give the order and type of values, as follows: a A string with arbitrary binary data, will be null padded. - A An ASCII string, will be space padded. - Z A null terminated (asciz) string, will be null padded. + A A text (ASCII) string, will be space padded. + Z A null terminated (ASCIZ) string, will be null padded. b A bit string (ascending bit order inside each byte, like vec()). B A bit string (descending bit order inside each byte). @@ -3029,8 +3104,8 @@ follows: P A pointer to a structure (fixed-length string). u A uuencoded string. - U A Unicode character number. Encodes to UTF-8 internally. - Works even if C is not in effect. + U A Unicode character number. Encodes to UTF-8 internally + (or UTF-EBCDIC in EBCDIC platforms). w A BER compressed integer. Its bytes represent an unsigned integer in base 128, most significant digit first, with as @@ -3189,14 +3264,14 @@ L: print $Config{longlongsize}, "\n"; (The C<$Config{longlongsize}> will be undefine if your system does -not support long longs.) +not support long longs.) =item * The integer formats C, C, C, C, C, and C are inherently non-portable between processors and operating systems because they obey the native byteorder and endianness. For example a -4-byte integer 0x12345678 (305419896 decimal) be ordered natively +4-byte integer 0x12345678 (305419896 decimal) would be ordered natively (arranged in and handled by the CPU registers) into bytes as 0x12 0x34 0x56 0x78 # big-endian @@ -3205,7 +3280,8 @@ because they obey the native byteorder and endianness. For example a Basically, the Intel and VAX CPUs are little-endian, while everybody else, for example Motorola m68k/88k, PPC, Sparc, HP PA, Power, and Cray are big-endian. Alpha and MIPS can be either: Digital/Compaq -used/uses them in little-endian mode; SGI/Cray uses them in big-endian mode. +used/uses them in little-endian mode; SGI/Cray uses them in big-endian +mode. The names `big-endian' and `little-endian' are comic references to the classic "Gulliver's Travels" (via the paper "On Holy Wars and a @@ -3232,7 +3308,7 @@ Byteorders C<'1234'> and C<'12345678'> are little-endian, C<'4321'> and C<'87654321'> are big-endian. If you want portable packed integers use the formats C, C, -C, and C, their byte endianness and size is known. +C, and C, their byte endianness and size are known. See also L. =item * @@ -3333,7 +3409,7 @@ The same template may generally also be used in unpack(). =item package NAMESPACE -=item package +=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 @@ -3352,8 +3428,10 @@ C<$::sail> is equivalent to C<$main::sail> (as well as to C<$main'sail>, still seen in older code). If NAMESPACE is omitted, then there is no current package, and all -identifiers must be fully qualified or lexicals. This is stricter -than C, since it also extends to function names. +identifiers must be fully qualified or lexicals. However, you are +strongly advised not to make use of this feature. Its use can cause +unexpected behaviour, even crashing some versions of Perl. It is +deprecated, and will be removed from a future release. See L for more information about packages, modules, and classes. See L for other scoping issues. @@ -3436,9 +3514,10 @@ you will have to use a block returning its value instead: Equivalent to C, except that C<$\> (the output record separator) is not appended. The first argument -of the list will be interpreted as the C format. If C is -in effect, the character used for the decimal point in formatted real numbers -is affected by the LC_NUMERIC locale. See L. +of the list will be interpreted as the C format. See C +for an explanation of the format argument. If C is in effect, +the character used for the decimal point in formatted real numbers is +affected by the LC_NUMERIC locale. See L. Don't fall into the trap of using a C when a simple C would do. The C is more efficient and less @@ -3475,12 +3554,10 @@ but is more efficient. Returns the new number of elements in the array. =item qr/STRING/ -=item qu/STRING/ +=item qx/STRING/ =item qw/STRING/ -=item qx/STRING/ - Generalized quotes. See L. =item quotemeta EXPR @@ -3502,8 +3579,15 @@ If EXPR is omitted, uses C<$_>. Returns a random fractional number greater than or equal to C<0> and less than the value of EXPR. (EXPR should be positive.) If EXPR is -omitted, the value C<1> is used. Automatically calls C unless -C has already been called. See also C. +omitted, or a C<0>, the value C<1> is used. Automatically calls C +unless C has already been called. See also C. + +Apply C to the value returned by C if you want random +integers instead of random fractional numbers. For example, + + int(rand(10)) + +returns a random integer between C<0> and C<9>, inclusive. (Note: If your rand function consistently returns numbers that are too large or too small, then your version of Perl was probably compiled @@ -3654,7 +3738,7 @@ name is returned instead. You can think of C as a C operator. } if (UNIVERSAL::isa($r, "HASH")) { # for subclassing print "r is a reference to something that isa hash.\n"; - } + } See also L. @@ -3676,19 +3760,23 @@ rename(2) manpage or equivalent system documentation for details. =item require -Demands some semantics specified by EXPR, or by C<$_> if EXPR is not -supplied. +Demands a version of Perl specified by VERSION, or demands some semantics +specified by EXPR or by C<$_> if EXPR is not supplied. -If a VERSION is specified as a literal of the form v5.6.1, -demands that the current version of Perl (C<$^V> or $PERL_VERSION) be -at least as recent as that version, at run time. (For compatibility -with older versions of Perl, a numeric argument will also be interpreted -as VERSION.) Compare with L, which can do a similar check at -compile time. +VERSION may be either a numeric argument such as 5.006, which will be +compared to C<$]>, or a literal of the form v5.6.1, which will be compared +to C<$^V> (aka $PERL_VERSION). A fatal error is produced at run time if +VERSION is greater than the version of the current Perl interpreter. +Compare with L, which can do a similar check at compile time. + +Specifying VERSION as a literal of the form v5.6.1 should generally be +avoided, because it leads to misleading error messages under earlier +versions of Perl which do not support this syntax. The equivalent numeric +version should be used instead. require v5.6.1; # run time version check require 5.6.1; # ditto - require 5.005_03; # float version allowed for compatibility + require 5.006_001; # ditto; preferred for backwards compatibility Otherwise, 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 @@ -3730,9 +3818,9 @@ modules does not risk altering your namespace. In other words, if you try this: - require Foo::Bar; # a splendid bareword + require Foo::Bar; # a splendid bareword -The require function will actually look for the "F" file in the +The require function will actually look for the "F" file in the directories specified in the C<@INC> array. But if you try this: @@ -3742,11 +3830,65 @@ But if you try this: #or require "Foo::Bar"; # not a bareword because of the "" -The require function will look for the "F" file in the @INC array and +The require function will look for the "F" file in the @INC array and will complain about not finding "F" there. In this case you can do: eval "require $class"; +You can also insert hooks into the import facility, by putting directly +Perl code into the @INC array. There are three forms of hooks: subroutine +references, array references and blessed objects. + +Subroutine references are the simplest case. When the inclusion system +walks through @INC and encounters a subroutine, this subroutine gets +called with two parameters, the first being a reference to itself, and the +second the name of the file to be included (e.g. "F"). The +subroutine should return C or a filehandle, from which the file to +include will be read. If C is returned, C will look at +the remaining elements of @INC. + +If the hook is an array reference, its first element must be a subroutine +reference. This subroutine is called as above, but the first parameter is +the array reference. This enables to pass indirectly some arguments to +the subroutine. + +In other words, you can write: + + push @INC, \&my_sub; + sub my_sub { + my ($coderef, $filename) = @_; # $coderef is \&my_sub + ... + } + +or: + + push @INC, [ \&my_sub, $x, $y, ... ]; + sub my_sub { + my ($arrayref, $filename) = @_; + # Retrieve $x, $y, ... + my @parameters = @$arrayref[1..$#$arrayref]; + ... + } + +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
.) Here is a typical code layout: + + # In Foo.pm + package Foo; + sub new { ... } + sub Foo::INC { + my ($self, $filename) = @_; + ... + } + + # In the main program + push @INC, new Foo(...); + +Note that these hooks are also permitted to set the %INC entry +corresponding to the files they have loaded. See L. + For a yet-more-powerful import facility, see L and L. =item reset EXPR @@ -3776,7 +3918,7 @@ See L. =item return -Returns from a subroutine, C, or C with the value +Returns from a subroutine, C, or C with the value given in EXPR. Evaluation of EXPR may be in list, scalar, or void context, depending on how the return value will be used, and the context may vary from one execution to the next (see C). If no EXPR @@ -3973,7 +4115,7 @@ calling select() in scalar context just returns $nfound. Any of the bit masks can also be undef. The timeout, if specified, is in seconds, which may be fractional. Note: not all implementations are -capable of returning the$timeleft. If not, they always return +capable of returning the $timeleft. If not, they always return $timeleft equal to the supplied $timeout. You can effect a sleep of 250 milliseconds this way: @@ -4009,14 +4151,14 @@ documentation. =item semop KEY,OPSTRING Calls the System V IPC function semop to perform semaphore operations -such as signaling and waiting. OPSTRING must be a packed array of +such as signalling and waiting. OPSTRING must be a packed array of semop structures. Each semop structure can be generated with -C. The number of semaphore +C. The number of semaphore operations is implied by the length of OPSTRING. Returns true if successful, or false if there is an error. As an example, the following code waits on semaphore $semnum of semaphore id $semid: - $semop = pack("sss", $semnum, -1, 0); + $semop = pack("s!3", $semnum, -1, 0); die "Semaphore trouble: $!\n" unless semop($semid, $semop); To signal the semaphore, replace C<-1> with C<1>. See also @@ -4113,7 +4255,7 @@ has the same interpretation as in the system call of the same name. This is useful with sockets when you want to tell the other side you're done writing but not done reading, or vice versa. -It's also a more insistent form of close because it also +It's also a more insistent form of close because it also disables the file descriptor in any forked copies in other processes. @@ -4147,11 +4289,32 @@ busy multitasking system. For delays of finer granularity than one second, you may use Perl's C interface to access setitimer(2) if your system supports -it, or else see L above. The Time::HiRes module from CPAN -may also help. +it, or else see L above. The Time::HiRes module (from CPAN, +and starting from Perl 5.8 part of the standard distribution) may also +help. See also the POSIX module's C function. +=item sockatmark SOCKET + +Returns true if the socket is positioned at the out-of-band mark +(also known as the urgent data mark), false otherwise. Use right +after reading from the socket. + +Not available directly, one has to import the function from +the IO::Socket extension + + use IO::Socket 'sockatmark'; + +Even this doesn't guarantee that sockatmark() really is available, +though, because sockatmark() is a relatively recent addition to +the family of socket functions. If it is unavailable, attempt to +use it will fail + + IO::Socket::atmark not implemented on this architecture ... + +See also L. + =item socket SOCKET,DOMAIN,TYPE,PROTOCOL Opens a socket of the specified kind and attaches it to filehandle @@ -4219,6 +4382,12 @@ loop control operators described in L or with C. When C is in effect, C sorts LIST according to the current collation locale. See L. +Perl does B guarantee that sort is stable. (A I sort +preserves the input order of elements that compare equal.) 5.7 and +5.8 happen to use a stable mergesort, but 5.6 and earlier used quicksort, +which is not stable. Do not assume that future perls will continue to +use a stable sort. + Examples: # sort lexically @@ -4375,11 +4544,15 @@ splits on whitespace (after skipping any leading whitespace). Anything matching PATTERN is taken to be a delimiter separating the fields. (Note that the delimiter may be longer than one character.) -If LIMIT is specified and positive, splits into no more than that -many fields (though it may split into fewer). If LIMIT is unspecified -or zero, trailing null fields are stripped (which potential users -of C would do well to remember). If LIMIT is negative, it is -treated as if an arbitrarily large LIMIT had been specified. +If LIMIT is specified and positive, it represents the maximum number +of fields the EXPR will be split into, though the actual number of +fields returned depends on the number of times PATTERN matches within +EXPR. If LIMIT is unspecified or zero, trailing null fields are +stripped (which potential users of C would do well to remember). +If LIMIT is negative, it is treated as if an arbitrarily large LIMIT +had been specified. Note that splitting an EXPR that evaluates to the +empty string always returns the empty list, regardless of the LIMIT +specified. A pattern matching the null string (not to be confused with a null pattern C, which is just one member of the set of patterns @@ -4390,6 +4563,10 @@ characters at each point it matches that way. For example: produces the output 'h:i:t:h:e:r:e'. +Using the empty pattern C specifically matches the null string, and is +not be confused with the use of C to mean "the last successful pattern +match". + Empty leading (or trailing) fields are produced when there positive width matches at the beginning (or end) of the string; a zero-width match at the beginning (or end) of the string does not produce an empty field. For @@ -4443,13 +4620,17 @@ Example: open(PASSWD, '/etc/passwd'); while () { - ($login, $passwd, $uid, $gid, + chomp; + ($login, $passwd, $uid, $gid, $gcos, $home, $shell) = split(/:/); #... } -(Note that $shell above will still have a newline on it. See L, -L, and L.) +As with regular pattern matching, any capturing parentheses that are not +matched in a C will be set to C when returned: + + @fields = split /(A)|B/, "1A2B3"; + # @fields is (1, 'A', 2, undef, 3) =item sprintf FORMAT, LIST @@ -4499,7 +4680,7 @@ In addition, Perl permits the following widely-supported conversions: %b an unsigned integer, in binary %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 + into the next variable in the parameter list Finally, for backward (and we do mean "backward") compatibility, Perl permits these unnecessary but widely-supported conversions: @@ -4628,19 +4809,42 @@ loaded the standard Math::Complex module. =item srand -Sets the random number seed for the C operator. If EXPR is -omitted, uses a semi-random value supplied by the kernel (if it supports -the F device) or based on the current time and process -ID, among other things. In versions of Perl prior to 5.004 the default -seed was just the current C