Free water filters software for linux

Units-filter is a basic standalone filter written in C, flex, and bison.
It inputs strings like "1.5e3 nN.m.s^-1" (which could be the time growth ratio of a torque) and outputs the value in standard SI units, followed by the physical dimension of this value.
units-filter can be embedded in educational test systems, in order to analyze a students answer to a problem of physics or chemistry.
Enhancements:
- The support for quantities with a particular number of significative digits was added.
- For example, the entry "1.02m#5" or "1.0200m" are equivalent and signify a distance measurement precise at the sub-millimeter scale.
- Both would yield the output "1.0200e+00 m".

IOLib-Filters is a filter package for IOLib. IOLib-Filters is mainly an example of how to write filters for IOLib.

IOLib is a portable universal data IO library. Implementations exist in C, C++ and Objective C and for many different platforms (including Linux, Win32, MacOS X and .NET).

IOLib provides a unified interface for accessing different types of data streams. It currently supports file IO, BSD sockets, memory buffers and SOCKS4/5 connections and can be extended with drivers easily.

It has support for different binary formats (Intel, Motorola, PDP) and it supports filters. You can write your own filters (e.g. for encryption or compression) and use them with IOLib.

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
);

INTRODUCTION

File::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 Perls concept of a line can be changed by setting $/, so the filters functions 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.

OPTIONS

A few options determine how the filters subroutine works.

binmode

Binmode 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,
);

boutmode

Boutmode 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:

ABCDEFGHIJKL

The following program should write three letters at a time to the output file:
filters (

source.txt,
$/ => 3,
sub { $_ = "$_n"; 1 },
dest.txt,
);

NOTES

Alternate function name

If you consider the function name filters to be too generic, you can import the name filter_funcs instead.

Convenience return values

For the programmers 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
);

Shrew Proxy/Filter is a tiny proxy built on WEBricks HTTPProxyServer, extended for both URL and content filtering. Shrew Proxy/Filter is designed to be small, simple to configure, and easy to install.

It is extremely small, lightweight, and works quite well. All blacklists (both URL and content) are plain text, so most published lists can be simply dropped in and used.