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17 Cards in this Set
- Front
- Back
$_
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• The most recently read input record.1
• Used automatically by print and many other built-in functions. |
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$"
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• The string inserted between the elements of a hash or array whose @-name
appears within double quotes (e.g., “@ARGV”). • Set to a space by default. |
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$0
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The name by which the script was invoked (e.g., “pgrep”); for a Perl command,
shows “-e”. |
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$$
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• The process-ID number of the Shell or Perl program.
|
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$.
|
• The ordinal number of the most recently read input record.2
• In END{ }, provides the total number of records read.2 |
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$/
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• A string that defines the characters (the input record separator) that mark the
end of an input record. • Automatically stripped by the -l option from the end of each input record read by the –n or -p option. • By default, set to an OS-specific character sequence (represented by “\n” ). • $/='-*-' means input records are terminated by -*-. • $/="" is a special case; means input records are terminated by one or more blank lines (paragraph mode). • $/=undef is a special case; means each file is one input record (file mode). • The input record separator can also be set via the -0digits option. |
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$\
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• A string that defines the characters (the output record separator) that are
appended after print’s last argument by the -l option. • By default, set to an OS-specific character sequence (represented by “\n” ). • $\='-*-' means output records are terminated by -*-. |
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$?
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• Contains the OS-specific exit code for the OS-command most recently run
via system or command interpolation (e.g., `date`) • On Unix systems, contains an exit code that looks to Perl like False on success and True on failure. |
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$!
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• Contains the OS-specific exit code (when used in numeric context) or error
message (in string context) for the last failed command run via system or command interpolation (e.g., system 'who'). • Shouldn’t be accessed unless “$?” indicates command failure, because “$!” isn’t reset by successful commands. |
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$a, $b
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• When they appear within sort’s code block or sub, these are the global variables
that contain the next pair of items to be compared. |
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$^I
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• The variable that controls in-place editing.
• Its contents define the file extension used on the backup copy of the edited file. • Typically set through use of the –i.ext option. |
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ARGV
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• The filehandle of the file that most recently provided input.4
|
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$ARGV
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• The name of the file that most recently provided input.
|
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@ARGV
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• The array that contains the program’s command-line arguments.
• Contents are interpreted as filenames in programs that read input automatically. |
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$#array
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The maximum index usable with @array (one less than the current number
of elements). |
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@F
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The array that contains the fields of the most recently read input record
(requires options -n or –p, and -a). |
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%ENV
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The hash that contains the program’s environment variables (on Unix, keys
are HOME, PATH, etc.). |