ptx (Unix)

ptx is a Unix utility that generates a permuted index of input text. A permuted index, also known as a keyword-in-context (KWIC) index, lists each keyword in the input along with its surrounding context, allowing users to quickly find occurrences of specific terms within a document. The ptx command is typically used for indexing technical manuals, code, or other textual documents.

The ptx command reads input from standard input or specified files and writes its output to standard output. Its output consists of lines representing each occurrence of a "significant" word (as determined by the program's configuration or user-specified options) within the input. Each output line is formatted to show the context surrounding the significant word, with the word itself prominently displayed. The display is arranged into three parts: a left context, the keyword itself, and a right context. ptx can perform various text transformations, such as ignoring certain words, adjusting the line length, and sorting the output. Options control the manner in which the lines are shifted and displayed.

Common uses of ptx include creating indices for documents, generating keyword lists, and preparing input for typesetting systems like troff or TeX. The tool has options for handling different languages and character sets and can be customized to fit specific indexing needs. ptx is part of the GNU coreutils package and is therefore widely available on Unix-like operating systems.