A filter is a computer program to process a data stream. Some operating systems such as Unix are rich with filter programs. Even Windows has some simple filters built in to its command shell, most of which have significant enhancements relative to the similar filter commands that were available in MS-DOS. Look up Data stream in Wiktionary, the free dictionary. ... An operating system (OS) is a computer program that manages the hardware and software resources of a computer. ... In UNIX and UNIX-like operating systems, a filter is program that gets most of its data from standard input and writes its main results to standard output. ... Microsoft Windows is the name of several families of proprietary software operating systems by Microsoft. ... It has been suggested that this article or section be merged with Operating_system_shell. ... Microsofts disk operating system, MS-DOS, was Microsofts implementation of DOS, which was the first popular operating system for the IBM PC, and until recently, was widely used on the PC compatible platform. ...

Just as in Unix, such a filter usually gets most of its data from standard input (the main input stream) and writes its main results to standard output (the main output stream). The command syntax for getting data from a device or file other than standard input is the input operator ("<"). Similarly, to send data to a device or file other than standard output is the output operator (">"). To append data lines to an existing output file, one can use the append operator (">>"). The standard streams are a set of input and output channels featured in Unix and Unix-like operating systems, and provided by the standard I/O library (stdio. ... The standard streams are a set of input and output channels featured in Unix and Unix-like operating systems, and provided by the standard I/O library (stdio. ...

The similarity with Unix extends to filters used as elements of pipelines. The pipe operator ("|") on a command line signifies that the main output of the command to the left is passed as main input to the command on the right. From the early days of DOS based computers, the two classic filters are find and sort. For the EP by Hidden in Plain View, see Find (EP) The find program is a search utility, mostly found on Unix-like platforms. ... In computer science and mathematics, a sorting algorithm is an algorithm that puts elements of a list in a certain order. ...

Examples:

• find "keyword" < inputfilename > outputfilename
• sort "keyword" < inputfilename > outputfilename
• find /v "keyword" < inputfilename | sort > outputfilename

Such filters may be used in batch files (*.bat, *.cmd etc.). In DOS and Windows, a batch file is a text file with a series of commands (see command line interface). ...

For use in the same command shell environment, there are many more filters available than those built in to Windows. Some of these are freeware, some shareware and some are commercial programs. A number of these mimic the function and features of the filters in Unix. Some filtering programs have a graphical user interface (GUI) to enable users to design a customized filter to suit their special data processing and/or data mining requirements. This article or section does not cite its references or sources. ... Look up shareware in Wiktionary, the free dictionary. ... A graphical user interface (or GUI, often pronounced gooey), is a particular case of user interface for interacting with a computer which employs graphical images and widgets in addition to text to represent the information and actions available to the user. ... Data processing is any computer process that converts data into information or knowledge. ... Data mining (DM), also called Knowledge-Discovery in Databases (KDD) or Knowledge-Discovery and Data Mining, is the process of automatically searching large volumes of data for patterns using tools such as classification, association rule mining, clustering, etc. ...

See also

• Filter (Unix)