m4

M4 is a powerful command line tool for Unix-like operating systems that processes text files. It is primarily used for macro processing and text generation. The "m4" stands for "macro processor version 4" as it is the fourth major release of the tool. M4 reads input files that contain macro calls and expands those macros based on predefined or custom-defined rules. These macros can contain variables, arithmetic expressions, control flow directives, and more. The tool is known for its simplicity in designing and writing macros and its extensibility. It offers a wide range of built-in functions and supports user-defined functions as well. M4 is commonly utilized in various scenarios, including generating code, configuration file management, and transforming text files with dynamic content. It finds applications in software development, system administration, and document processing. The command line syntax for using the m4 tool is straightforward, allowing users to specify input and output files, as well as additional options and macro definitions. M4 is compatible with POSIX standards and is available as open-source software on most Unix-like systems. It has influenced several other macro processors and has a long history, dating back to the 1970s. Despite its age, M4 remains a widely used tool due to its simplicity, flexibility, and robustness. It provides a versatile solution for automating text manipulation tasks and facilitating code generation.