Follow Techotopia on Twitter

On-line Guides
All Guides
eBook Store
iOS / Android
Linux for Beginners
Office Productivity
Linux Installation
Linux Security
Linux Utilities
Linux Virtualization
Linux Kernel
System/Network Admin
Scripting Languages
Development Tools
Web Development
GUI Toolkits/Desktop
Mail Systems
Eclipse Documentation

How To Guides
General System Admin
Linux Security
Linux Filesystems
Web Servers
Graphics & Desktop
PC Hardware
Problem Solutions
Privacy Policy




Back: Looping
Forward: Including files
FastBack: Including files
Up: Features of M4
FastForward: Writing macros within the GNU Autotools framework
Top: Autoconf, Automake, and Libtool
Contents: Table of Contents
Index: Index
About: About this document

21.4.5 Diversions

Diversions are a facility in M4 for diverting text from the input stream into a holding buffer. There is a large number of diversion buffers in GNU M4, limited only by available memory. Text can be diverted into any one of these buffers and then `undiverted' back to the output (diversion number 0) at a later stage.

Text is diverted and undiverted using the divert and undivert macros. They expand to the empty string, with the side effect of setting the diversion. Here is an illustrative example:

This goes at the end.
This goes at the beginning.
=>This goes at the beginning.
=>This goes at the end.

It is unlikely that you will want to use diversions in your own macros, and it is difficult to do reliably without understanding the internals of Autoconf. However, it is interesting to note that this is how autoconf generates fragments of shell code on-the-fly that must precede shell code at the current point in the `configure' script.

This document was generated by Gary V. Vaughan on February, 8 2006 using texi2html

  Published under the terms of the Open Publication License Design by Interspire