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perl 内置预定义变量

发布时间:2020-12-15 20:52:15 所属栏目:大数据 来源:网络整理
导读:perl预定义变量 $ARG $_ - The default input and pattern-searching space. $digit - Contains the subpattern from the corresponding set of parentheses in the last pattern matched. $MATCH $ - The string matched by the last successful pattern ma

perl预定义变量

$ARG
$_
- The default input and pattern-searching space.
$<digit> - Contains the subpattern from the corresponding set of parentheses in the last pattern matched.
$MATCH
$&
- The string matched by the last successful pattern match.
$PREMATCH
$`
- The string preceding whatever was matched by the last successful pattern match.
$POSTMATCH
$'
- The string following whatever was matched by the last successful pattern match.
$LAST_PAREN_MATCH
$+
- The last bracket matched by the last search pattern.
$MULTILINE_MATCHING
$*
- Set to 1 to do multi-line matching within a string,0 to tell Perl that it can assume that strings contain a single line,for the purpose of optimizing pattern matches. Default is 0. Use of ``$*'' is deprecated in modern perls.
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).
input_record_separator HANDLE EXPR
$INPUT_RECORD_SEPARATOR
$RS
$/
- The input record separator,newline by default.
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.
output_field_separator HANDLE EXPR
$OUTPUT_FIELD_SEPARATOR
$OFS
$,
- The output field separator for the print operator.
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.
$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.
$SUBSCRIPT_SEPARATOR
$SUBSEP
$;
- The subscript separator for multidimensional array emulation.
$OFMT
$#
- The output format for printed numbers. Use of ``$#'' is deprecated.
format_page_number HANDLE EXPR
$FORMAT_PAGE_NUMBER
$%
- The current page number of the currently selected output channel.
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.
format_lines_left HANDLE EXPR
$FORMAT_LINES_LEFT
$-
- The number of lines left on the page of the currently selected output channel.
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.
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.
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.
format_formfeed HANDLE EXPR
$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.
$CHILD_ERROR
$?
- The status returned by the last pipe close,backtick (``) command,or system() operator.
$OS_ERROR
$ERRNO
$!
- If used in a numeric context,yields the current value of errno,with all the usual caveats. If used in a string context,yields the corresponding system error string.
$EXTENDED_OS_ERROR
$^E
- More specific information about the last system error than that provided by $!,if available. (If not,it's just $! again,except under OS/2.)
$EVAL_ERROR
$@
- The Perl syntax error message from the last eval() command.
$PROCESS_ID
$PID
$$
- The process number of the Perl running this script.
$REAL_USER_ID
$UID
$<
- The real uid of this process.
$EFFECTIVE_USER_ID
$EUID
$>
- The effective uid of this process.
$REAL_GROUP_ID
$GID
$(
- The real gid of this process.
$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.
$PROGRAM_NAME
- Contains the name of the file containing the Perl script being executed.
$[ - The index of the first element in an array,and of the first character in a substring. As of Perl 5,assignment to ``$['' is treated as a compiler directive,and cannot influence the behavior of any other file. Its use is discouraged.
$PERL_VERSION
$]
- The version + patchlevel / 1000 of the Perl interpreter.
$DEBUGGING
$^D
- The current value of the debugging flags.
$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.
$^H - The current set of syntax checks enabled by use strict.
$INPLACE_EDIT
$^I
- The current value of the inplace-edit extension.
$OSNAME
$^O
- The name of the operating system under which this copy of Perl was built,as determined during the configuration process.
$PERLDB
$^P
- The internal variable for debugging support.
$BASETIME
$^T
- The time at which the script began running.
$WARNING
$^W
- The current value of the warning 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.
@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.
%INC - The hash %INC contains entries for each filename that has been included via do or require.
$ENV - The hash %ENV contains your current environment. Setting a value in ENV changes the environment for child processes.
$SIG - The hash %SIG is used to set signal handlers for various signals. Example:
$^M -emergency memory pool

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