perlvar man page on BSDi

Man page or keyword search:  
man Server   6284 pages
apropos Keyword Search (all sections)
Output format
BSDi logo
[printable version]



PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

NAME
       perlvar - Perl predefined variables

DESCRIPTION
       Predefined Names

       The following names have special meaning to Perl.  Most
       punctuation names have reasonable mnemonics, or analogues
       in one of the shells.  Nevertheless, if you wish to use
       long variable names, you just need to say

	   use English;

       at the top of your program.  This will alias all the short
       names to the long names in the current package.	Some even
       have medium names, generally borrowed from awk.

       Due to an unfortunate accident of Perl's implementation,
       "use English" imposes a considerable performance penalty
       on all regular expression matches in a program, regardless
       of whether they occur in the scope of "use English".  For
       that reason, saying "use English" in libraries is strongly
       discouraged.  See the Devel::SawAmpersand module
       documentation from CPAN
       (http://www.perl.com/CPAN/modules/by-module/Devel/Devel-
       SawAmpersand-0.10.readme) for more information.

       To go a step further, those variables that depend on the
       currently selected filehandle may instead (and preferably)
       be set by calling an object method on the FileHandle
       object.	(Summary lines below for this contain the word
       HANDLE.)	 First you must say

	   use FileHandle;

       after which you may use either

	   method HANDLE EXPR

       or more safely,

	   HANDLE->method(EXPR)

       Each of the methods returns the old value of the
       FileHandle attribute.  The methods each take an optional
       EXPR, which if supplied specifies the new value for the
       FileHandle attribute in question.  If not supplied, most
       of the methods do nothing to the current value, except for
       autoflush(), which will assume a 1 for you, just to be
       different.

       A few of these variables are considered "read-only".  This
       means that if you try to assign to this variable, either
       directly or indirectly through a reference, you'll raise a

16/Sep/1999	       perl 5.005, patch 03			1

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       run-time exception.

       The following list is ordered by scalar variables first,
       then the arrays, then the hashes (except $^M was added in
       the wrong place).  This is somewhat obscured by the fact
       that %ENV and %SIG are listed as $ENV{expr} and
       $SIG{expr}.

       $ARG

       $_      The default input and pattern-searching space.
	       The following pairs are equivalent:

		   while (<>) {...}    # equivalent in only while!
		   while (defined($_ = <>)) {...}

		   /^Subject:/
		   $_ =~ /^Subject:/

		   tr/a-z/A-Z/
		   $_ =~ tr/a-z/A-Z/

		   chop
		   chop($_)

	       Here are the places where Perl will assume $_ even
	       if you don't use it:

       o	  Various unary functions, including functions
		  like ord() and int(), as well as the all file
		  tests (-f, -d) except for -t, which defaults to
		  STDIN.

       o	  Various list functions like print() and
		  unlink().

       o	  The pattern matching operations m//, s///, and
		  tr/// when used without an =~ operator.

       o	  The default iterator variable in a foreach loop
		  if no other variable is supplied.

       o	  The implicit iterator variable in the grep()
		  and map() functions.

       o	  The default place to put an input record when a
		  <FH> operation's result is tested by itself as
		  the sole criterion of a while test.  Note that
		  outside of a while test, this will not happen.

		  (Mnemonic: underline is understood in certain
		  operations.)

16/Sep/1999	       perl 5.005, patch 03			2

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       $<digits>
	       Contains the subpattern from the corresponding set
	       of parentheses in the last pattern matched, not
	       counting patterns matched in nested blocks that
	       have been exited already.  (Mnemonic: like
	       \digits.)  These variables are all read-only.

       $MATCH

       $&      The string matched by the last successful pattern
	       match (not counting any matches hidden within a
	       BLOCK or eval() enclosed by the current BLOCK).
	       (Mnemonic: like & in some editors.)  This variable
	       is read-only.

	       The use of this variable anywhere in a program
	       imposes a considerable performance penalty on all
	       regular expression matches.  See the
	       Devel::SawAmpersand module from CPAN for more
	       information.

       $PREMATCH

       $`      The string preceding whatever was matched by the
	       last successful pattern match (not counting any
	       matches hidden within a BLOCK or eval enclosed by
	       the current BLOCK).  (Mnemonic: ` often precedes a
	       quoted string.)	This variable is read-only.

	       The use of this variable anywhere in a program
	       imposes a considerable performance penalty on all
	       regular expression matches.  See the
	       Devel::SawAmpersand module from CPAN for more
	       information.

       $POSTMATCH

       $'      The string following whatever was matched by the
	       last successful pattern match (not counting any
	       matches hidden within a BLOCK or eval() enclosed
	       by the current BLOCK).  (Mnemonic: ' often follows
	       a quoted string.)  Example:

		   $_ = 'abcdefghi';
		   /def/;
		   print "$`:$&:$'\n";	       # prints abc:def:ghi

	       This variable is read-only.

	       The use of this variable anywhere in a program
	       imposes a considerable performance penalty on all
	       regular expression matches.  See the
	       Devel::SawAmpersand module from CPAN for more
	       information.

16/Sep/1999	       perl 5.005, patch 03			3

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       $LAST_PAREN_MATCH

       $+      The last bracket matched by the last search
	       pattern.	 This is useful if you don't know which
	       of a set of alternative patterns matched.  For
	       example:

		   /Version: (.*)|Revision: (.*)/ && ($rev = $+);

	       (Mnemonic: be positive and forward looking.)  This
	       variable is read-only.

       $MULTILINE_MATCHING

       $*      Set to 1 to do multi-line matching within a
	       string, 0 to tell Perl that it can assume that
	       strings contain a single line, for the purpose of
	       optimizing pattern matches.  Pattern matches on
	       strings containing multiple newlines can produce
	       confusing results when "$*" is 0.  Default is 0.
	       (Mnemonic: * matches multiple things.)  Note that
	       this variable influences the interpretation of
	       only "^" and "$".  A literal newline can be
	       searched for even when $* == 0.

	       Use of "$*" is deprecated in modern Perls,
	       supplanted by the /s and /m modifiers on pattern
	       matching.

       input_line_number HANDLE EXPR

       $INPUT_LINE_NUMBER

       $NR

       $.      The current input line number for the last file
	       handle from which you read (or performed a seek or
	       tell on).  The value may be different from the
	       actual physical line number in the file, depending
	       on what notion of "line" is in effect--see the
	       section on $/ on how to affect that.  An explicit
	       close on a filehandle resets the line number.
	       Because "<>" never does an explicit close, line
	       numbers increase across ARGV files (but see
	       examples under eof()).  Localizing $. has the
	       effect of also localizing Perl's notion of "the
	       last read filehandle".  (Mnemonic: many programs
	       use "." to mean the current line number.)

       input_record_separator HANDLE EXPR

       $INPUT_RECORD_SEPARATOR

16/Sep/1999	       perl 5.005, patch 03			4

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       $RS

       $/      The input record separator, newline by default.
	       This is used to influence Perl's idea of what a
	       "line" is.  Works like awk's RS variable,
	       including treating empty lines as delimiters if
	       set to the null string.	(Note: An empty line
	       cannot contain any spaces or tabs.)  You may set
	       it to a multi-character string to match a multi-
	       character delimiter, or to undef to read to end of
	       file.  Note that setting it to "\n\n" means
	       something slightly different than setting it to
	       "", if the file contains consecutive empty lines.
	       Setting it to "" will treat two or more
	       consecutive empty lines as a single empty line.
	       Setting it to "\n\n" will blindly assume that the
	       next input character belongs to the next
	       paragraph, even if it's a newline.  (Mnemonic: /
	       is used to delimit line boundaries when quoting
	       poetry.)

		   undef $/;	       # enable "slurp" mode
		   $_ = <FH>;	       # whole file now here
		   s/\n[ \t]+/ /g;

	       Remember: the value of $/ is a string, not a
	       regexp.	AWK has to be better for something :-)

	       Setting $/ to a reference to an integer, scalar
	       containing an integer, or scalar that's
	       convertable to an integer will attempt to read
	       records instead of lines, with the maximum record
	       size being the referenced integer. So this:

		   $/ = \32768; # or \"32768", or \$var_containing_32768
		   open(FILE, $myfile);
		   $_ = <FILE>;

	       will read a record of no more than 32768 bytes
	       from FILE. If you're not reading from a record-
	       oriented file (or your OS doesn't have record-
	       oriented files), then you'll likely get a full
	       chunk of data with every read. If a record is
	       larger than the record size you've set, you'll get
	       the record back in pieces.

	       On VMS, record reads are done with the equivalent
	       of sysread, so it's best not to mix record and
	       non-record reads on the same file. (This is likely
	       not a problem, as any file you'd want to read in
	       record mode is probably usable in line mode) Non-
	       VMS systems perform normal I/O, so it's safe to
	       mix record and non-record reads of a file.

16/Sep/1999	       perl 5.005, patch 03			5

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

	       Also see the section on $..

       autoflush HANDLE EXPR

       $OUTPUT_AUTOFLUSH

       $|      If set to nonzero, forces a flush right away and
	       after every write or print on the currently
	       selected output channel.	 Default is 0 (regardless
	       of whether the channel is actually buffered by the
	       system or not; $| tells you only whether you've
	       asked Perl explicitly to flush after each write).
	       Note that STDOUT will typically be line buffered
	       if output is to the terminal and block buffered
	       otherwise.  Setting this variable is useful
	       primarily when you are outputting to a pipe, such
	       as when you are running a Perl script under rsh
	       and want to see the output as it's happening.
	       This has no effect on input buffering.  (Mnemonic:
	       when you want your pipes to be piping hot.)

       output_field_separator HANDLE EXPR

       $OUTPUT_FIELD_SEPARATOR

       $OFS

       $,      The output field separator for the print operator.
	       Ordinarily the print operator simply prints out
	       the comma-separated fields you specify.	To get
	       behavior more like awk, set this variable as you
	       would set awk's OFS variable to specify what is
	       printed between fields.	(Mnemonic: what is
	       printed when there is a , in your print
	       statement.)

       output_record_separator HANDLE EXPR

       $OUTPUT_RECORD_SEPARATOR

       $ORS

       $\      The output record separator for the print
	       operator.  Ordinarily the print operator simply
	       prints out the comma-separated fields you specify,
	       with no trailing newline or record separator
	       assumed.	 To get behavior more like awk, set this
	       variable as you would set awk's ORS variable to
	       specify what is printed at the end of the print.
	       (Mnemonic: you set "$\" instead of adding \n at
	       the end of the print.  Also, it's just like $/,
	       but it's what you get "back" from Perl.)

16/Sep/1999	       perl 5.005, patch 03			6

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       $LIST_SEPARATOR

       $""""   This is like "$," except that it applies to array
	       values interpolated into a double-quoted string
	       (or similar interpreted string).	 Default is a
	       space.  (Mnemonic: obvious, I think.)

       $SUBSCRIPT_SEPARATOR

       $SUBSEP

       $;      The subscript separator for multidimensional array
	       emulation.  If you refer to a hash element as

		   $foo{$a,$b,$c}

	       it really means

		   $foo{join($;, $a, $b, $c)}

	       But don't put

		   @foo{$a,$b,$c}      # a slice--note the @

	       which means

		   ($foo{$a},$foo{$b},$foo{$c})

	       Default is "\034", the same as SUBSEP in awk.
	       Note that if your keys contain binary data there
	       might not be any safe value for "$;".  (Mnemonic:
	       comma (the syntactic subscript separator) is a
	       semi-semicolon.	Yeah, I know, it's pretty lame,
	       but "$," is already taken for something more
	       important.)

	       Consider using "real" multidimensional arrays.

       $OFMT

       $#      The output format for printed numbers.  This
	       variable is a half-hearted attempt to emulate
	       awk's OFMT variable.  There are times, however,
	       when awk and Perl have differing notions of what
	       is in fact numeric.  The initial value is %.ng,
	       where n is the value of the macro DBL_DIG from
	       your system's float.h.  This is different from
	       awk's default OFMT setting of %.6g, so you need to
	       set "$#" explicitly to get awk's value.
	       (Mnemonic: # is the number sign.)

	       Use of "$#" is deprecated.

16/Sep/1999	       perl 5.005, patch 03			7

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       format_page_number HANDLE EXPR

       $FORMAT_PAGE_NUMBER

       $%      The current page number of the currently selected
	       output channel.	(Mnemonic: % is page number in
	       nroff.)

       format_lines_per_page HANDLE EXPR

       $FORMAT_LINES_PER_PAGE

       $=      The current page length (printable lines) of the
	       currently selected output channel.  Default is 60.
	       (Mnemonic: = has horizontal lines.)

       format_lines_left HANDLE EXPR

       $FORMAT_LINES_LEFT

       $-      The number of lines left on the page of the
	       currently selected output channel.  (Mnemonic:
	       lines_on_page - lines_printed.)

       format_name HANDLE EXPR

       $FORMAT_NAME

       $~      The name of the current report format for the
	       currently selected output channel.  Default is
	       name of the filehandle.	(Mnemonic: brother to
	       "$^".)

       format_top_name HANDLE EXPR

       $FORMAT_TOP_NAME

       $^      The name of the current top-of-page format for the
	       currently selected output channel.  Default is
	       name of the filehandle with _TOP appended.
	       (Mnemonic: points to top of page.)

       format_line_break_characters HANDLE EXPR

       $FORMAT_LINE_BREAK_CHARACTERS

       $:      The current set of characters after which a string
	       may be broken to fill continuation fields
	       (starting with ^) in a format.  Default is " \n-",
	       to break on whitespace or hyphens.  (Mnemonic: a
	       "colon" in poetry is a part of a line.)

       format_formfeed HANDLE EXPR

16/Sep/1999	       perl 5.005, patch 03			8

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       $FORMAT_FORMFEED

       $^L     What formats output to perform a form feed.
	       Default is \f.

       $ACCUMULATOR

       $^A     The current value of the write() accumulator for
	       format() lines.	A format contains formline()
	       commands that put their result into $^A.	 After
	       calling its format, write() prints out the
	       contents of $^A and empties.  So you never
	       actually see the contents of $^A unless you call
	       formline() yourself and then look at it.	 See the
	       perlform manpage and the formline() entry in the
	       perlfunc manpage.

       $CHILD_ERROR

       $?      The status returned by the last pipe close,
	       backtick (``) command, or system() operator.  Note
	       that this is the status word returned by the
	       wait() system call (or else is made up to look
	       like it).  Thus, the exit value of the subprocess
	       is actually ($? >> 8), and $? & 127 gives which
	       signal, if any, the process died from, and $? &
	       128 reports whether there was a core dump.
	       (Mnemonic: similar to sh and ksh.)

	       Additionally, if the h_errno variable is supported
	       in C, its value is returned via $? if any of the
	       gethost*() functions fail.

	       Note that if you have installed a signal handler
	       for SIGCHLD, the value of $? will usually be wrong
	       outside that handler.

	       Inside an END subroutine $? contains the value
	       that is going to be given to exit().  You can
	       modify $? in an END subroutine to change the exit
	       status of the script.

	       Under VMS, the pragma use vmsish 'status' makes $?
	       reflect the actual VMS exit status, instead of the
	       default emulation of POSIX status.

	       Also see the section on Error Indicators.

       $OS_ERROR

       $ERRNO

       $!      If used in a numeric context, yields the current
	       value of errno, with all the usual caveats.  (This

16/Sep/1999	       perl 5.005, patch 03			9

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

	       means that you shouldn't depend on the value of $!
	       to be anything in particular unless you've gotten
	       a specific error return indicating a system
	       error.)	If used in a string context, yields the
	       corresponding system error string.  You can assign
	       to $! to set errno if, for instance, you want "$!"
	       to return the string for error n, or you want to
	       set the exit value for the die() operator.
	       (Mnemonic: What just went bang?)

	       Also see the section on Error Indicators.

       $EXTENDED_OS_ERROR

       $^E     Error information specific to the current
	       operating system.  At the moment, this differs
	       from $! under only VMS, OS/2, and Win32 (and for
	       MacPerl).  On all other platforms, $^E is always
	       just the same as $!.

	       Under VMS, $^E provides the VMS status value from
	       the last system error.  This is more specific
	       information about the last system error than that
	       provided by $!.	This is particularly important
	       when $! is set to EVMSERR.

	       Under OS/2, $^E is set to the error code of the
	       last call to OS/2 API either via CRT, or directly
	       from perl.

	       Under Win32, $^E always returns the last error
	       information reported by the Win32 call
	       GetLastError() which describes the last error from
	       within the Win32 API.  Most Win32-specific code
	       will report errors via $^E.  ANSI C and UNIX-like
	       calls set errno and so most portable Perl code
	       will report errors via $!.

	       Caveats mentioned in the description of $!
	       generally apply to $^E, also.  (Mnemonic: Extra
	       error explanation.)

	       Also see the section on Error Indicators.

       $EVAL_ERROR

       $@      The Perl syntax error message from the last eval()
	       command.	 If null, the last eval() parsed and
	       executed correctly (although the operations you
	       invoked may have failed in the normal fashion).
	       (Mnemonic: Where was the syntax error "at"?)

	       Note that warning messages are not collected in
	       this variable.  You can, however, set up a routine

16/Sep/1999	       perl 5.005, patch 03		       10

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

	       to process warnings by setting $SIG{__WARN__} as
	       described below.

	       Also see the section on Error Indicators.

       $PROCESS_ID

       $PID

       $$      The process number of the Perl running this
	       script.	(Mnemonic: same as shells.)

       $REAL_USER_ID

       $UID

       $<      The real uid of this process.  (Mnemonic: it's the
	       uid you came FROM, if you're running setuid.)

       $EFFECTIVE_USER_ID

       $EUID

       $>      The effective uid of this process.  Example:

		   $< = $>;	       # set real to effective uid
		   ($<,$>) = ($>,$<);  # swap real and effective uid

	       (Mnemonic: it's the uid you went TO, if you're
	       running setuid.)	 Note: "$<" and "$>" can be
	       swapped only on machines supporting setreuid().

       $REAL_GROUP_ID

       $GID

       $(      The real gid of this process.  If you are on a
	       machine that supports membership in multiple
	       groups simultaneously, gives a space separated
	       list of groups you are in.  The first number is
	       the one returned by getgid(), and the subsequent
	       ones by getgroups(), one of which may be the same
	       as the first number.

	       However, a value assigned to "$(" must be a single
	       number used to set the real gid.	 So the value
	       given by "$(" should not be assigned back to "$("
	       without being forced numeric, such as by adding
	       zero.

	       (Mnemonic: parentheses are used to GROUP things.
	       The real gid is the group you LEFT, if you're
	       running setgid.)

16/Sep/1999	       perl 5.005, patch 03		       11

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       $EFFECTIVE_GROUP_ID

       $EGID

       $)      The effective gid of this process.  If you are on
	       a machine that supports membership in multiple
	       groups simultaneously, gives a space separated
	       list of groups you are in.  The first number is
	       the one returned by getegid(), and the subsequent
	       ones by getgroups(), one of which may be the same
	       as the first number.

	       Similarly, a value assigned to "$)" must also be a
	       space-separated list of numbers.	 The first number
	       is used to set the effective gid, and the rest (if
	       any) are passed to setgroups().	To get the effect
	       of an empty list for setgroups(), just repeat the
	       new effective gid; that is, to force an effective
	       gid of 5 and an effectively empty setgroups()
	       list, say  $) = "5 5" .

	       (Mnemonic: parentheses are used to GROUP things.
	       The effective gid is the group that's RIGHT for
	       you, if you're running setgid.)

	       Note: "$<", "$>", "$(" and "$)" can be set only on
	       machines that support the corresponding
	       set[re][ug]id() routine.	 "$(" and "$)" can be
	       swapped only on machines supporting setregid().

       $PROGRAM_NAME

       $0      Contains the name of the file containing the Perl
	       script being executed.  On some operating systems
	       assigning to "$0" modifies the argument area that
	       the ps(1) program sees.	This is more useful as a
	       way of indicating the current program state than
	       it is for hiding the program you're running.
	       (Mnemonic: same as sh and ksh.)

       $[      The index of the first element in an array, and of
	       the first character in a substring.  Default is 0,
	       but you could set it to 1 to make Perl behave more
	       like awk (or Fortran) when subscripting and when
	       evaluating the index() and substr() functions.
	       (Mnemonic: [ begins subscripts.)

	       As of Perl 5, assignment to "$[" is treated as a
	       compiler directive, and cannot influence the
	       behavior of any other file.  Its use is
	       discouraged.

       $PERL_VERSION

16/Sep/1999	       perl 5.005, patch 03		       12

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       $]      The version + patchlevel / 1000 of the Perl
	       interpreter.  This variable can be used to
	       determine whether the Perl interpreter executing a
	       script is in the right range of versions.
	       (Mnemonic: Is this version of perl in the right
	       bracket?)  Example:

		   warn "No checksumming!\n" if $] < 3.019;

	       See also the documentation of use VERSION and
	       require VERSION for a convenient way to fail if
	       the Perl interpreter is too old.

       $COMPILING

       $^C     The current value of the flag associated with the
	       -c switch. Mainly of use with -MO=... to allow
	       code to alter its behaviour when being compiled.
	       (For example to automatically AUTOLOADing at
	       compile time rather than normal deferred loading.)
	       Setting $^C = 1 is similar to calling B::minus_c.

       $DEBUGGING

       $^D     The current value of the debugging flags.
	       (Mnemonic: value of -D switch.)

       $SYSTEM_FD_MAX

       $^F     The maximum system file descriptor, ordinarily 2.
	       System file descriptors are passed to exec()ed
	       processes, while higher file descriptors are not.
	       Also, during an open(), system file descriptors
	       are preserved even if the open() fails.	(Ordinary
	       file descriptors are closed before the open() is
	       attempted.)  Note that the close-on-exec status of
	       a file descriptor will be decided according to the
	       value of $^F when the open() or pipe() was called,
	       not the time of the exec().

       $^H     The current set of syntax checks enabled by use
	       strict and other block scoped compiler hints.  See
	       the documentation of strict for more details.

       $INPLACE_EDIT

       $^I     The current value of the inplace-edit extension.
	       Use undef to disable inplace editing.  (Mnemonic:
	       value of -i switch.)

       $^M     By default, running out of memory it is not
	       trappable.  However, if compiled for this, Perl
	       may use the contents of $^M as an emergency pool
	       after die()ing with this message.  Suppose that

16/Sep/1999	       perl 5.005, patch 03		       13

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

	       your Perl were compiled with -DPERL_EMERGENCY_SBRK
	       and used Perl's malloc.	Then

		   $^M = 'a' x (1<<16);

	       would allocate a 64K buffer for use when in
	       emergency.  See the INSTALL file for information
	       on how to enable this option.  As a disincentive
	       to casual use of this advanced feature, there is
	       no the English manpage long name for this
	       variable.

       $OSNAME

       $^O     The name of the operating system under which this
	       copy of Perl was built, as determined during the
	       configuration process.  The value is identical to
	       $Config{'osname'}.

       $PERLDB

       $^P     The internal variable for debugging support.
	       Different bits mean the following (subject to
	       change):

       0x01	     Debug subroutine enter/exit.

       0x02	     Line-by-line debugging.

       0x04	     Switch off optimizations.

       0x08	     Preserve more data for future interactive
		     inspections.

       0x10	     Keep info about source lines on which a
		     subroutine is defined.

       0x20	     Start with single-step on.

		     Note that some bits may be relevant at
		     compile-time only, some at run-time only.
		     This is a new mechanism and the details may
		     change.

       $^R     The result of evaluation of the last successful
	       the section on (?{ code }) in the perlre manpage
	       regular expression assertion.  (Excluding those
	       used as switches.)  May be written to.

       $^S     Current state of the interpreter.  Undefined if
	       parsing of the current module/eval is not finished
	       (may happen in $SIG{__DIE__} and $SIG{__WARN__}
	       handlers).  True if inside an eval, otherwise
	       false.

16/Sep/1999	       perl 5.005, patch 03		       14

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       $BASETIME

       $^T     The time at which the script began running, in
	       seconds since the epoch (beginning of 1970).  The
	       values returned by the -M, -A, and -C filetests
	       are based on this value.

       $WARNING

       $^W     The current value of the warning switch, either
	       TRUE or FALSE.  (Mnemonic: related to the -w
	       switch.)

       $EXECUTABLE_NAME

       $^X     The name that the Perl binary itself was executed
	       as, from C's argv[0].

       $ARGV   contains the name of the current file when reading
	       from <>.

       @ARGV   The array @ARGV contains the command line
	       arguments intended for the script.  Note that
	       $#ARGV is the generally number of arguments minus
	       one, because $ARGV[0] is the first argument, NOT
	       the command name.  See "$0" for the command name.

       @INC    The array @INC contains the list of places to look
	       for Perl scripts to be evaluated by the do EXPR,
	       require, or use constructs.  It initially consists
	       of the arguments to any -I command line switches,
	       followed by the default Perl library, probably
	       /usr/local/lib/perl, followed by ".", to represent
	       the current directory.  If you need to modify this
	       at runtime, you should use the use lib pragma to
	       get the machine-dependent library properly loaded
	       also:

		   use lib '/mypath/libdir/';
		   use SomeMod;

       @_      Within a subroutine the array @_ contains the
	       parameters passed to that subroutine. See the
	       perlsub manpage.

       %INC    The hash %INC contains entries for each filename
	       that has been included via do or require.  The key
	       is the filename you specified, and the value is
	       the location of the file actually found.	 The
	       require command uses this array to determine
	       whether a given file has already been included.

16/Sep/1999	       perl 5.005, patch 03		       15

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       %ENV

       $ENV{expr}
	       The hash %ENV contains your current environment.
	       Setting a value in ENV changes the environment for
	       child processes.

       %SIG

       $SIG{expr}
	       The hash %SIG is used to set signal handlers for
	       various signals.	 Example:

		   sub handler {       # 1st argument is signal name
		       my($sig) = @_;
		       print "Caught a SIG$sig--shutting down\n";
		       close(LOG);
		       exit(0);
		   }

		   $SIG{'INT'}	= \&handler;
		   $SIG{'QUIT'} = \&handler;
		   ...
		   $SIG{'INT'} = 'DEFAULT';    # restore default action
		   $SIG{'QUIT'} = 'IGNORE';    # ignore SIGQUIT

	       Using a value of 'IGNORE' usually has the effect
	       of ignoring the signal, except for the CHLD
	       signal.	See the perlipc manpage for more about
	       this special case.

	       The %SIG array contains values for only the
	       signals actually set within the Perl script.  Here
	       are some other examples:

		   $SIG{"PIPE"} = Plumber;     # SCARY!!
		   $SIG{"PIPE"} = "Plumber";   # assumes main::Plumber (not recommended)
		   $SIG{"PIPE"} = \&Plumber;   # just fine; assume current Plumber
		   $SIG{"PIPE"} = Plumber();   # oops, what did Plumber() return??

	       The one marked scary is problematic because it's a
	       bareword, which means sometimes it's a string
	       representing the function, and sometimes it's
	       going to call the subroutine call right then and
	       there!  Best to be sure and quote it or take a
	       reference to it.	 *Plumber works too.  See the
	       perlsub manpage.

	       If your system has the sigaction() function then
	       signal handlers are installed using it.	This
	       means you get reliable signal handling.	If your
	       system has the SA_RESTART flag it is used when
	       signals handlers are installed.	This means that
	       system calls for which it is supported continue

16/Sep/1999	       perl 5.005, patch 03		       16

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

	       rather than returning when a signal arrives.  If
	       you want your system calls to be interrupted by
	       signal delivery then do something like this:

		   use POSIX ':signal_h';

		   my $alarm = 0;
		   sigaction SIGALRM, new POSIX::SigAction sub { $alarm = 1 }
		       or die "Error setting SIGALRM handler: $!\n";

	       See the POSIX manpage.

	       Certain internal hooks can be also set using the
	       %SIG hash.  The routine indicated by
	       $SIG{__WARN__} is called when a warning message is
	       about to be printed.  The warning message is
	       passed as the first argument.  The presence of a
	       __WARN__ hook causes the ordinary printing of
	       warnings to STDERR to be suppressed.  You can use
	       this to save warnings in a variable, or turn
	       warnings into fatal errors, like this:

		   local $SIG{__WARN__} = sub { die $_[0] };
		   eval $proggie;

	       The routine indicated by $SIG{__DIE__} is called
	       when a fatal exception is about to be thrown.  The
	       error message is passed as the first argument.
	       When a __DIE__ hook routine returns, the exception
	       processing continues as it would have in the
	       absence of the hook, unless the hook routine
	       itself exits via a goto, a loop exit, or a die().
	       The __DIE__ handler is explicitly disabled during
	       the call, so that you can die from a __DIE__
	       handler.	 Similarly for __WARN__.

	       Note that the $SIG{__DIE__} hook is called even
	       inside eval()ed blocks/strings.	See the die entry
	       in the perlfunc manpage and the section on $^S in
	       the perlvar manpage for how to circumvent this.

	       Note that __DIE__/__WARN__ handlers are very
	       special in one respect: they may be called to
	       report (probable) errors found by the parser.  In
	       such a case the parser may be in inconsistent
	       state, so any attempt to evaluate Perl code from
	       such a handler will probably result in a segfault.
	       This means that calls which result/may-result in
	       parsing Perl should be used with extreme caution,
	       like this:

16/Sep/1999	       perl 5.005, patch 03		       17

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

		   require Carp if defined $^S;
		   Carp::confess("Something wrong") if defined &Carp::confess;
		   die "Something wrong, but could not load Carp to give backtrace...
			To see backtrace try starting Perl with -MCarp switch";

	       Here the first line will load Carp unless it is
	       the parser who called the handler.  The second
	       line will print backtrace and die if Carp was
	       available.  The third line will be executed only
	       if Carp was not available.

	       See the die entry in the perlfunc manpage, the
	       warn entry in the perlfunc manpage and the eval
	       entry in the perlfunc manpage for additional info.

       Error Indicators

       The variables the section on $@, the section on $!, the
       section on $^E, and the section on $? contain information
       about different types of error conditions that may appear
       during execution of Perl script.	 The variables are shown
       ordered by the "distance" between the subsystem which
       reported the error and the Perl process, and correspond to
       errors detected by the Perl interpreter, C library,
       operating system, or an external program, respectively.

       To illustrate the differences between these variables,
       consider the following Perl expression:

	  eval '
		open PIPE, "/cdrom/install |";
		@res = <PIPE>;
		close PIPE or die "bad pipe: $?, $!";
	       ';

       After execution of this statement all 4 variables may have
       been set.

       $@ is set if the string to be eval-ed did not compile
       (this may happen if open or close were imported with bad
       prototypes), or if Perl code executed during evaluation
       die()d (either implicitly, say, if open was imported from
       module the Fatal manpage, or the die after close was
       triggered).  In these cases the value of $@ is the compile
       error, or Fatal error (which will interpolate $!!), or the
       argument to die (which will interpolate $! and $?!).

       When the above expression is executed, open(), <PIPE>, and
       close are translated to C run-time library calls.  $! is
       set if one of these calls fails.	 The value is a symbolic
       indicator chosen by the C run-time library, say No such
       file or directory.

       On some systems the above C library calls are further

16/Sep/1999	       perl 5.005, patch 03		       18

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

       translated to calls to the kernel.  The kernel may have
       set more verbose error indicator that one of the handful
       of standard C errors.  In such cases $^E contains this
       verbose error indicator, which may be, say, CDROM tray not
       closed.	On systems where C library calls are identical to
       system calls $^E is a duplicate of $!.

       Finally, $? may be set to non-0 value if the external
       program /cdrom/install fails.  Upper bits of the
       particular value may reflect specific error conditions
       encountered by this program (this is program-dependent),
       lower-bits reflect mode of failure (segfault, completion,
       etc.).  Note that in contrast to $@, $!, and $^E, which
       are set only if error condition is detected, the variable
       $? is set on each wait or pipe close, overwriting the old
       value.

       For more details, see the individual descriptions at the
       section on $@, the section on $!, the section on $^E, and
       the section on $?.

       Technical Note on the Syntax of Variable Names

       Variable names in Perl can have several formats.	 Usually,
       they must begin with a letter or underscore, in which case
       they can be arbitrarily long (up to an internal limit of
       256 characters) and may contain letters, digits,
       underscores, or the special sequence ::.	 In this case the
       part before the last :: is taken to be a package
       qualifier; see the perlmod manpage.

       Perl variable names may also be a sequence of digits or a
       single punctuation or control character.	 These names are
       all reserved for special uses by Perl; for example, the
       all-digits names are used to hold backreferences after a
       regular expression match.  Perl has a special syntax for
       the single-control-character names: It understands ^X
       (caret X) to mean the control-X character.  For example,
       the notation $^W (dollar-sign caret W) is the scalar
       variable whose name is the single character control-W.
       This is better than typing a literal control-W into your
       program.

       All Perl variables that begin with digits, control
       characters, or punctuation characters are exempt from the
       effects of the package declaration and are always forced
       to be in package main.  A few other names are also exempt:

	       ENV	       STDIN
	       INC	       STDOUT
	       ARGV	       STDERR
	       ARGVOUT
	       SIG

16/Sep/1999	       perl 5.005, patch 03		       19

PERLVAR(1)	 Perl Programmers Reference Guide      PERLVAR(1)

16/Sep/1999	       perl 5.005, patch 03		       20

[top]

List of man pages available for BSDi

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net