File::FilterFuncs File::FilterFuncs is a Perl module that specify filter functions for files.
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Perl module file filter file filter functions specify filter functions

File::FilterFuncs Description

File::FilterFuncs is a Perl module that specify filter functions for files. File::FilterFuncs is a Perl module that specify filter functions for files.SYNOPSIS use File::FilterFuncs qw(filters); filters('source.txt', sub { $_ = uc $_; 1 }, 'dest.txt' );INTRODUCTIONFile::FilterFuncs makes it easy to perform transformations on files. When you use this module, you specify a group of filter functions that perform transformations on the lines in a source file. Those transformed lines are written to the destination file that you specify. For example, this code converts an entire file to upper-case, line-by-line: use File::FilterFuncs qw(filters); filters('source.txt', sub { $_ = uc $_; 1 }, 'dest.txt' );The "1" at the end of the filter subroutine tells filters to keep all the lines. The filter subroutine should return 1 for any lines that should be kept, and it should return 0 for any lines that should be ignored. This program copies only lines that contain something besides just whitespace: use File::FilterFuncs qw(filters); filters('source.txt', sub { /S/ }, 'dest.txt' );The entire source file is not read into memory. Instead it is read one line at a time, and the destination file is written one line at a time.Just as Perl's concept of a line can be changed by setting $/, so the filters function's idea of a line can also be changed by specifying a value for $/ in the call to filters: my $pad = "" x 2; filters('source.dat', '$/' => 1022, sub { $_ .= $pad; 1 }, 'dest.dat' );Filter functions are invoked in the order in which they are seen. This code upper-cases then puts inside parenthses every line in 'source.txt' and copies the output to 'dest.txt': filters ('source.txt', sub { $_ = uc $_; 1 }, sub { chomp $_; $_ = "($_)n"; 1 }, 'dest.txt' );Obviously, the current line that is being worked on is in $_.The filters subroutine expects its first argument to be the name of the source file, and the last argument should be the name of the destination file. The function filters will die if either one of the file names is missing or if they are inaccessible.OPTIONSA few options determine how the filters subroutine works.binmodeBinmode lets you specify a layer to be used for the input data. For example, this will read a utf-8 file and write the data using the default output layer: filters ( 'source.txt', binmode => ':utf8', 'dest.txt', );boutmodeBoutmode lets the programmer specify a layer to be used for writing the output data. For example, this code on a Linux platform should read text data using the Linux end-of-line format and write it using the DOS (CRLF) end-of-line format: filters ( 'source.txt', boutmode => ':crlf', 'dest.txt', );$/Setting $/ lets you determine how an end-of-line is recognized. Set this option to the same value that you would set the $/ variable to in a program. For example, suppose a file contains this: ABCDEFGHIJKLThe following program should write three letters at a time to the output file: filters ( 'source.txt', '$/' => 3, sub { $_ = "$_n"; 1 }, 'dest.txt', );NOTESAlternate function nameIf you consider the function name filters to be too generic, you can import the name filter_funcs instead.Convenience return valuesFor the programmer's convenience and to facilitate self-documenting code, the values $KEEP_LINE and $IGNORE_LINE can be exported. As an example, this is another program to filter out lines containing only whitespace: use File::FilterFuncs qw(filters $IGNORE_LINE); filters('source.txt', sub { return $IGNORE_LINE unless /S/ }, 'dest.txt' ); Requirements: · Perl

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