home *** CD-ROM | disk | FTP | other *** search
- <!-- $RCSfile$$Revision$$Date$ -->
- <!-- $Log$ -->
- <HTML>
- <TITLE> PERLVAR </TITLE>
- <h2>NAME</h2>
- perlvar - Perl predefined variables
- <p><h2>DESCRIPTION</h2>
- <h3>Predefined Names</h3>
- The following names have special meaning to Perl. Most of the
- punctuational names have reasonable mnemonics, or analogues in one of
- the shells. Nevertheless, if you wish to use the long variable names,
- you just need to say
- <p><pre>
- use English;
- </pre>
- at the top of your program. This will alias all the short names to the
- long names in the current package. Some of them even have medium names,
- generally borrowed from <B>awk</B>.
- <p>To go a step further, those variables that depend on the currently
- selected filehandle may instead be set by calling an object method on
- the FileHandle object. (Summary lines below for this contain the word
- HANDLE.) First you must say
- <p><pre>
- use FileHandle;
- </pre>
- after which you may use either
- <p><pre>
- method HANDLE EXPR
- </pre>
- or
- <p><pre>
- HANDLE->method(EXPR)
- </pre>
- 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.
- <p>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. If you attempt to do so, you'll raise a run-time exception.
- <p>
- <dl>
-
- <dt><b><A NAME="perlvar_370">$ARG</A></b>
-
- <dt><b><A NAME="perlvar_371">$_</A></b>
- <dd>
- The default input and pattern-searching space. The following pairs are
- equivalent:
- <p></dd>
- <pre>
- while (<>) {...} # only equivalent in while!
- while ($_ = <>) {...}
- </pre>
- <pre>
- /^Subject:/
- $_ =~ /^Subject:/
- </pre>
- <pre>
- tr/a-z/A-Z/
- $_ =~ tr/a-z/A-Z/
- </pre>
- <pre>
- chop
- chop($_)
- </pre>
- (Mnemonic: underline is understood in certain operations.)
- <p><dt><B>$<<I>digit</I>></B>
- <dd>
- Contains the subpattern from the corresponding set of parentheses in
- the last pattern matched, not counting patterns matched in nested
- blocks that have been exited already. (Mnemonic: like \digit.)
- These variables are all read-only.
- <p></dd>
-
- <dt><b><A NAME="perlvar_373">$MATCH</A></b>
- <dt><B>$&</B>
- <dd>
- The string matched by the last successful pattern match (not counting
- any matches hidden within a BLOCK or eval() enclosed by the current
- BLOCK). (Mnemonic: like & in some editors.) This variable is read-only.
- <p></dd>
-
- <dt><b><A NAME="perlvar_375">$PREMATCH</A></b>
-
- <dt><b><A NAME="perlvar_376">$`</A></b>
- <dd>
- The string preceding whatever was matched by the last successful
- pattern match (not counting any matches hidden within a BLOCK or eval
- enclosed by the current BLOCK). (Mnemonic: ` often precedes a quoted
- string.) This variable is read-only.
- <p></dd>
-
- <dt><b><A NAME="perlvar_377">$POSTMATCH</A></b>
-
- <dt><b><A NAME="perlvar_378">$'</A></b>
- <dd>
- 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:
- <p></dd>
- <pre>
- $_ = 'abcdefghi';
- /def/;
- print "$`:$&:$'\n"; # prints abc:def:ghi
- </pre>
- This variable is read-only.
- <p>
- <dt><b><A NAME="perlvar_379">$LAST_PAREN_MATCH</A></b>
-
- <dt><b><A NAME="perlvar_380">$+</A></b>
- <dd>
- 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:
- <p></dd>
- <pre>
- /Version: (.*)|Revision: (.*)/ && ($rev = $+);
- </pre>
- (Mnemonic: be positive and forward looking.)
- This variable is read-only.
- <p>
- <dt><b><A NAME="perlvar_381">$MULTILINE_MATCHING</A></b>
-
- <dt><b><A NAME="perlvar_382">$*</A></b>
- <dd>
- Set to 1 to do multiline matching within a string, 0 to tell Perl
- that it can assume that strings contain a single line, for the purpose
- of optimizing pattern matches. Pattern matches on strings containing
- multiple newlines can produce confusing results when "
- <A HREF="perlvar.html#perlvar_382">$*</A>
- " is 0. Default
- is 0. (Mnemonic: * matches multiple things.) Note that this variable
- only influences the interpretation of "<B>^</B>" and "<B>$</B>". A literal newline can
- be searched for even when <B>$* == 0</B>.
- <p></dd>
- Use of "
- <A HREF="perlvar.html#perlvar_382">$*</A>
- " is deprecated in Perl 5.
- <p>
- <dt><b><A NAME="perlvar_383">input_line_number HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_384">$INPUT_LINE_NUMBER</A></b>
-
- <dt><b><A NAME="perlvar_385">$NR</A></b>
-
- <dt><b><A NAME="perlvar_386">$.</A></b>
- <dd>
- The current input line number of the last filehandle that was read.
- This variable should be considered read-only.
- Remember that only an explicit close on the filehandle
- resets the line number. Since "<B><></B>" never does an explicit close, line
- numbers increase across ARGV files (but see examples under eof()).
- (Mnemonic: many programs use "." to mean the current line number.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_387">input_record_separator HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_388">$INPUT_RECORD_SEPARATOR</A></b>
-
- <dt><b><A NAME="perlvar_389">$RS</A></b>
-
- <dt><b><A NAME="perlvar_390">$/</A></b>
- <dd>
- The input record separator, newline by default. Works like <B>awk</B>'s RS
- variable, including treating blank lines as delimiters if set to the
- null string. You may set it to a multicharacter string to match a
- multi-character delimiter. Note that setting it to <B>"\n\n"</B> means
- something slightly different than setting it to <B>""</B>, if the file
- contains consecutive blank lines. Setting it to <B>""</B> will treat two or
- more consecutive blank lines as a single blank line. Setting it to
- <B>"\n\n"</B> 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.)
- <p></dd>
- <pre>
- undef $/;
- $_ = <FH>; # whole file now here
- s/\n[ \t]+/ /g;
- </pre>
-
- <dt><b><A NAME="perlvar_391">autoflush HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_392">$OUTPUT_AUTOFLUSH</A></b>
-
- <dt><b><A NAME="perlvar_393">$|</A></b>
- <dd>
- If set to nonzero, forces a flush after every write or print on the
- currently selected output channel. Default is 0. Note that STDOUT
- will typically be line buffered if output is to the terminal and block
- buffered otherwise. Setting this variable is useful primarily when you
- are outputting to a pipe, such as when you are running a Perl script
- under rsh and want to see the output as it's happening. (Mnemonic:
- when you want your pipes to be piping hot.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_394">output_field_separator HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_395">$OUTPUT_FIELD_SEPARATOR</A></b>
-
- <dt><b><A NAME="perlvar_396">$OFS</A></b>
-
- <dt><b><A NAME="perlvar_397">$,</A></b>
- <dd>
- The output field separator for the print operator. Ordinarily the
- print operator simply prints out the comma separated fields you
- specify. In order to get behavior more like <B>awk</B>, set this variable
- as you would set <B>awk</B>'s OFS variable to specify what is printed
- between fields. (Mnemonic: what is printed when there is a , in your
- print statement.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_398">output_record_separator HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_399">$OUTPUT_RECORD_SEPARATOR</A></b>
-
- <dt><b><A NAME="perlvar_400">$ORS</A></b>
-
- <dt><b><A NAME="perlvar_401">$\</A></b>
- <dd>
- The output record separator for the print operator. Ordinarily the
- print operator simply prints out the comma separated fields you
- specify, with no trailing newline or record separator assumed. In
- order to get behavior more like <B>awk</B>, set this variable as you would
- set <B>awk</B>'s ORS variable to specify what is printed at the end of the
- print. (Mnemonic: you set "
- <A HREF="perlvar.html#perlvar_401">$\</A>
- " instead of adding \n at the end of the
- print. Also, it's just like /, but it's what you get "back" from
- Perl.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_402">$LIST_SEPARATOR</A></b>
-
- <dt><b><A NAME="perlvar_403">$"</A></b>
- <dd>
- This is like "
- <A HREF="perlvar.html#perlvar_397">$,</A>
- " except that it applies to array values interpolated
- into a double-quoted string (or similar interpreted string). Default
- is a space. (Mnemonic: obvious, I think.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_404">$SUBSCRIPT_SEPARATOR</A></b>
-
- <dt><b><A NAME="perlvar_405">$SUBSEP</A></b>
-
- <dt><b><A NAME="perlvar_406">$;</A></b>
- <dd>
- The subscript separator for multi-dimensional array emulation. If you
- refer to a hash element as
- <p></dd>
- <pre>
- $foo{$a,$b,$c}
- </pre>
- it really means
- <p><pre>
- $foo{join($;, $a, $b, $c)}
- </pre>
- But don't put
- <p><pre>
- @foo{$a,$b,$c} # a slice--note the @
- </pre>
- which means
- <p><pre>
- ($foo{$a},$foo{$b},$foo{$c})
- </pre>
- Default is "\034", the same as SUBSEP in <B>awk</B>. Note that if your
- keys contain binary data there might not be any safe value for "
- <A HREF="perlvar.html#perlvar_406">$;</A>
- ".
- (Mnemonic: comma (the syntactic subscript separator) is a
- semi-semicolon. Yeah, I know, it's pretty lame, but "
- <A HREF="perlvar.html#perlvar_397">$,</A>
- " is already
- taken for something more important.)
- <p>Consider using "real" multi-dimensional arrays in Perl 5.
- <p>
- <dt><b><A NAME="perlvar_407">$OFMT</A></b>
-
- <dt><b><A NAME="perlvar_408">$#</A></b>
- <dd>
- The output format for printed numbers. This variable is a half-hearted
- attempt to emulate <B>awk</B>'s OFMT variable. There are times, however,
- when <B>awk</B> and Perl have differing notions of what is in fact
- numeric. Also, the initial value is %.20g rather than %.6g, so you
- need to set "
- <A HREF="perlvar.html#perlvar_408">$#</A>
- " explicitly to get <B>awk</B>'s value. (Mnemonic: # is the
- number sign.)
- <p></dd>
- Use of "
- <A HREF="perlvar.html#perlvar_408">$#</A>
- " is deprecated in Perl 5.
- <p>
- <dt><b><A NAME="perlvar_409">format_page_number HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_410">$FORMAT_PAGE_NUMBER</A></b>
-
- <dt><b><A NAME="perlvar_411">$%</A></b>
- <dd>
- The current page number of the currently selected output channel.
- (Mnemonic: % is page number in <B>nroff</B>.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_412">format_lines_per_page HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_413">$FORMAT_LINES_PER_PAGE</A></b>
-
- <dt><b><A NAME="perlvar_414">$=</A></b>
- <dd>
- The current page length (printable lines) of the currently selected
- output channel. Default is 60. (Mnemonic: = has horizontal lines.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_415">format_lines_left HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_416">$FORMAT_LINES_LEFT</A></b>
-
- <dt><b><A NAME="perlvar_417">$-</A></b>
- <dd>
- The number of lines left on the page of the currently selected output
- channel. (Mnemonic: lines_on_page - lines_printed.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_418">format_name HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_419">$FORMAT_NAME</A></b>
-
- <dt><b><A NAME="perlvar_420">$~</A></b>
- <dd>
- The name of the current report format for the currently selected output
- channel. Default is name of the filehandle. (Mnemonic: brother to
- "
- <A HREF="perlvar.html#perlvar_423">$^</A>
- ".)
- <p></dd>
-
- <dt><b><A NAME="perlvar_421">format_top_name HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_422">$FORMAT_TOP_NAME</A></b>
-
- <dt><b><A NAME="perlvar_423">$^</A></b>
- <dd>
- The name of the current top-of-page format for the currently selected
- output channel. Default is name of the filehandle with _TOP
- appended. (Mnemonic: points to top of page.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_424">format_line_break_characters HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_425">$FORMAT_LINE_BREAK_CHARACTERS</A></b>
-
- <dt><b><A NAME="perlvar_426">$:</A></b>
- <dd>
- The current set of characters after which a string may be broken to
- fill continuation fields (starting with ^) in a format. Default is
- " \n-", to break on whitespace or hyphens. (Mnemonic: a "colon" in
- poetry is a part of a line.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_427">format_formfeed HANDLE EXPR</A></b>
-
- <dt><b><A NAME="perlvar_428">$FORMAT_FORMFEED</A></b>
-
- <dt><b><A NAME="perlvar_429">$^L</A></b>
- <dd>
- What formats output to perform a formfeed. Default is \f.
- <p></dd>
-
- <dt><b><A NAME="perlvar_430">$ACCUMULATOR</A></b>
-
- <dt><b><A NAME="perlvar_431">$^A</A></b>
- <dd>
- The current value of the write() accumulator for format() lines. A format
- contains formline() commands that put their result into
- <A HREF="perlvar.html#perlvar_431">$^A</A>
- . After
- calling its format, write() prints out the contents of
- <A HREF="perlvar.html#perlvar_431">$^A</A>
- and empties.
- So you never actually see the contents of
- <A HREF="perlvar.html#perlvar_431">$^A</A>
- unless you call
- formline() yourself and then look at it. See
- <A HREF="perlform.html">
- the perlform manpage</A>
- and
- perlfunc/formline().
- <p></dd>
-
- <dt><b><A NAME="perlvar_432">$CHILD_ERROR</A></b>
-
- <dt><b><A NAME="perlvar_433">$?</A></b>
- <dd>
- The status returned by the last pipe close, backtick (<B>``</B>) command,
- or system() operator. Note that this is the status word returned by
- the wait() system call, so the exit value of the subprocess is actually
- (<B>$? >> 8</B>). Thus on many systems, <B>$? & 255</B> gives which signal,
- if any, the process died from, and whether there was a core dump.
- (Mnemonic: similar to <B>sh</B> and <B>ksh</B>.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_434">$OS_ERROR</A></b>
-
- <dt><b><A NAME="perlvar_435">$ERRNO</A></b>
-
- <dt><b><A NAME="perlvar_436">$!</A></b>
- <dd>
- If used in a numeric context, yields the current value of errno, with
- all the usual caveats. (This means that you shouldn't depend on the
- value of "
- <A HREF="perlvar.html#perlvar_436">$!</A>
- " 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 "
- <A HREF="perlvar.html#perlvar_436">$!</A>
- " in order to set <I>errno</I> if, for instance, you want "
- <A HREF="perlvar.html#perlvar_436">$!</A>
- " to return the
- string for error <I>n</I>, or you want to set the exit value for the die()
- operator. (Mnemonic: What just went bang?)
- <p></dd>
-
- <dt><b><A NAME="perlvar_437">$EVAL_ERROR</A></b>
-
- <dt><b><A NAME="perlvar_438">$@</A></b>
- <dd>
- 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"?)
- <p></dd>
-
- <dt><b><A NAME="perlvar_439">$PROCESS_ID</A></b>
-
- <dt><b><A NAME="perlvar_440">$PID</A></b>
-
- <dt><b><A NAME="perlvar_441">$$</A></b>
- <dd>
- The process number of the Perl running this script. (Mnemonic: same
- as shells.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_442">$REAL_USER_ID</A></b>
-
- <dt><b><A NAME="perlvar_443">$UID</A></b>
- <dt><B>$<</B>
- <dd>
- The real uid of this process. (Mnemonic: it's the uid you came <I>FROM</I>,
- if you're running setuid.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_445">$EFFECTIVE_USER_ID</A></b>
-
- <dt><b><A NAME="perlvar_446">$EUID</A></b>
- <dt><B>$></B>
- <dd>
- The effective uid of this process. Example:
- <p></dd>
- <pre>
- $< = $>; # set real to effective uid
- ($<,$>) = ($>,$<); # swap real and effective uid
- </pre>
- (Mnemonic: it's the uid you went <I>TO</I>, if you're running setuid.) Note:
- "<B>$<</B>" and "<B>$></B>" can only be swapped on machines supporting setreuid().
- <p>
- <dt><b><A NAME="perlvar_448">$REAL_GROUP_ID</A></b>
-
- <dt><b><A NAME="perlvar_449">$GID</A></b>
-
- <dt><b><A NAME="perlvar_450">$(</A></b>
- <dd>
- 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. (Mnemonic: parentheses are used to <I>GROUP</I>
- things. The real gid is the group you <I>LEFT</I>, if you're running setgid.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_451">$EFFECTIVE_GROUP_ID</A></b>
-
- <dt><b><A NAME="perlvar_452">$EGID</A></b>
-
- <dt><b><A NAME="perlvar_453">$)</A></b>
- <dd>
- The effective gid of this process. If you are on a machine that
- supports membership in multiple groups simultaneously, gives a space
- separated list of groups you are in. The first number is the one
- returned by getegid(), and the subsequent ones by getgroups(), one of
- which may be the same as the first number. (Mnemonic: parentheses are
- used to <I>GROUP</I> things. The effective gid is the group that's <I>RIGHT</I> for
- you, if you're running setgid.)
- <p></dd>
- Note: "<B>$<</B>", "<B>$></B>", "
- <A HREF="perlvar.html#perlvar_450">$(</A>
- " and "
- <A HREF="perlvar.html#perlvar_453">$)</A>
- " can only be set on machines
- that support the corresponding <I>set[re][ug]id()</I> routine. "
- <A HREF="perlvar.html#perlvar_450">$(</A>
- " and "
- <A HREF="perlvar.html#perlvar_453">$)</A>
- "
- can only be swapped on machines supporting setregid().
- <p>
- <dt><b><A NAME="perlvar_454">$PROGRAM_NAME</A></b>
-
- <dt><b><A NAME="perlvar_455">$0</A></b>
- <dd>
- Contains the name of the file containing the Perl script being
- executed. Assigning to "
- <A HREF="perlvar.html#perlvar_455">$0</A>
- " modifies the argument area that the ps(1)
- program sees. This is more useful as a way of indicating the
- current program state than it is for hiding the program you're running.
- (Mnemonic: same as <B>sh</B> and <B>ksh</B>.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_456">$[</A></b>
- <dd>
- 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 <B>awk</B> (or Fortran) when subscripting and when
- evaluating the index() and substr() functions. (Mnemonic: [ begins
- subscripts.)
- <p></dd>
- As of Perl 5, assignment to "
- <A HREF="perlvar.html#perlvar_456">$[</A>
- " is treated as a compiler directive,
- and cannot influence the behavior of any other file. Its use is
- discouraged.
- <p>
- <dt><b><A NAME="perlvar_457">$PERL_VERSION</A></b>
-
- <dt><b><A NAME="perlvar_458">$]</A></b>
- <dd>
- The string printed out when you say <B>perl -v</B>. It can be used to
- determine at the beginning of a script whether the perl interpreter
- executing the script is in the right range of versions. If used in a
- numeric context, returns the version + patchlevel / 1000. Example:
- <p></dd>
- <pre>
- # see if getc is available
- ($version,$patchlevel) =
- $] =~ /(\d+\.\d+).*\nPatch level: (\d+)/;
- print STDERR "(No filename completion available.)\n"
- if $version * 1000 + $patchlevel < 2016;
- </pre>
- or, used numerically,
- <p><pre>
- warn "No checksumming!\n" if $] < 3.019;
- </pre>
- (Mnemonic: Is this version of perl in the right bracket?)
- <p>
- <dt><b><A NAME="perlvar_459">$DEBUGGING</A></b>
-
- <dt><b><A NAME="perlvar_460">$^D</A></b>
- <dd>
- The current value of the debugging flags. (Mnemonic: value of
- <A HREF="perlrun.html#perlrun_347">-D</A>
-
- switch.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_461">$SYSTEM_FD_MAX</A></b>
-
- <dt><b><A NAME="perlvar_462">$^F</A></b>
- <dd>
- The maximum system file descriptor, ordinarily 2. System file
- descriptors are passed to exec()ed processes, while higher file
- descriptors are not. Also, during an open(), system file descriptors are
- preserved even if the open() fails. (Ordinary file descriptors are
- closed before the open() is attempted.) Note that the close-on-exec
- status of a file descriptor will be decided according to the value of
-
- <A HREF="perlvar.html#perlvar_462">$^F</A>
- at the time of the open, not the time of the exec.
- <p></dd>
-
- <dt><b><A NAME="perlvar_463">$INPLACE_EDIT</A></b>
-
- <dt><b><A NAME="perlvar_464">$^I</A></b>
- <dd>
- The current value of the inplace-edit extension. Use
- <A HREF="perlfunc.html#perlfunc_258">undef</A>
- to disable
- inplace editing. (Mnemonic: value of
- <A HREF="perlrun.html#perlrun_350">-i</A>
- switch.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_465">$PERLDB</A></b>
-
- <dt><b><A NAME="perlvar_466">$^P</A></b>
- <dd>
- The internal flag that the debugger clears so that it doesn't debug
- itself. You could conceivable disable debugging yourself by clearing
- it.
- <p></dd>
-
- <dt><b><A NAME="perlvar_467">$BASETIME</A></b>
-
- <dt><b><A NAME="perlvar_468">$^T</A></b>
- <dd>
- The time at which the script began running, in seconds since the
- epoch (beginning of 1970). The values returned by the <B>-M</B>, <B>-A</B>
- and <B>-C</B> filetests are
- based on this value.
- <p></dd>
-
- <dt><b><A NAME="perlvar_469">$WARNING</A></b>
-
- <dt><b><A NAME="perlvar_470">$^W</A></b>
- <dd>
- The current value of the warning switch, either TRUE or FALSE. (Mnemonic: related to the
-
- <A HREF="perlrun.html#perlrun_362">-w</A>
- switch.)
- <p></dd>
-
- <dt><b><A NAME="perlvar_471">$EXECUTABLE_NAME</A></b>
-
- <dt><b><A NAME="perlvar_472">$^X</A></b>
- <dd>
- The name that the Perl binary itself was executed as, from C's <B>argv[0]</B>.
- <p></dd>
-
- <dt><b><A NAME="perlvar_473">$ARGV</A></b>
- <dd>
- contains the name of the current file when reading from <>.
- <p></dd>
-
- <dt><b><A NAME="perlvar_474">@ARGV</A></b>
- <dd>
- The array @ARGV contains the command line arguments intended for the
- script. Note that <B>$#ARGV</B> is the generally number of arguments minus
- one, since <B>$ARGV[0]</B> is the first argument, <I>NOT</I> the command name. See
- "
- <A HREF="perlvar.html#perlvar_455">$0</A>
- " for the command name.
- <p></dd>
-
- <dt><b><A NAME="perlvar_475">@INC</A></b>
- <dd>
- The array @INC contains the list of places to look for Perl scripts to
- be evaluated by the <B>do EXPR</B>,
- <A HREF="perlfunc.html#perlfunc_205">require</A>
- , or
- <A HREF="perlfunc.html#perlfunc_263">use</A>
- constructs. It
- initially consists of the arguments to any
- <A HREF="perlrun.html#perlrun_351">-I</A>
- command line switches,
- followed by the default Perl library, probably "/usr/local/lib/perl",
- followed by ".", to represent the current directory.
- <p></dd>
-
- <dt><b><A NAME="perlvar_476">%INC</A></b>
- <dd>
- The hash %INC contains entries for each filename that has
- been included via
- <A HREF="perlfunc.html#perlfunc_97">do</A>
- or
- <A HREF="perlfunc.html#perlfunc_205">require</A>
- . The key is the filename you
- specified, and the value is the location of the file actually found.
- The
- <A HREF="perlfunc.html#perlfunc_205">require</A>
- command uses this array to determine whether a given file
- has already been included.
- <p></dd>
-
- <dt><b><A NAME="perlvar_477">$ENV{expr}</A></b>
- <dd>
- The hash %ENV contains your current environment. Setting a
- value in <B>ENV</B> changes the environment for child processes.
- <p></dd>
-
- <dt><b><A NAME="perlvar_478">$SIG{expr}</A></b>
- <dd>
- The hash %SIG is used to set signal handlers for various
- signals. Example:
- <p></dd>
- <pre>
- sub handler { # 1st argument is signal name
- local($sig) = @_;
- print "Caught a SIG$sig--shutting down\n";
- close(LOG);
- exit(0);
- }
- </pre>
- <pre>
- $SIG{'INT'} = 'handler';
- $SIG{'QUIT'} = 'handler';
- ...
- $SIG{'INT'} = 'DEFAULT'; # restore default action
- $SIG{'QUIT'} = 'IGNORE'; # ignore SIGQUIT
- </pre>
- The %SIG array only contains values for the signals actually set within
- the Perl script. Here are some other examples:
- <p><pre>
- $SIG{PIPE} = Plumber; # SCARY!!
- $SIG{"PIPE"} = "Plumber"; # just fine, assumes main::Plumber
- $SIG{"PIPE"} = \&Plumber; # just fine; assume current Plumber
- $SIG{"PIPE"} = Plumber(); # oops, what did Plumber() return??
- </pre>
- 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 <perlsubs>.
- <p>
- </dl>
-
-
- </HTML>
-