Writing HTML with m4
m4 has a simple arithmetic facility with two operators m4_incr and m4_decr. This facility can be used to create automatic numbering, perhaps for headings, for example:
m4_define(_CARDINAL,0) m4_define(_H, `m4_define(`_CARDINAL', m4_incr(_CARDINAL))<H2>_CARDINAL.0 $1</H2>') _H(First Heading) _H(Second Heading)
<H2>1.0 First Heading</H2> <H2>2.0 Second Heading</H2>
For simple date stamping of HTML pages, I use the m4_esyscmd command to maintain an automatic timestamp on every page:
This page was updated on m4_esyscmd(date)
This page was last updated on Fri May 9 10:35:03 HKT 1997
Using m4 allows you to define commonly repeated phrases and use them consistently. I hate repeating myself because I am lazy and because I make mistakes, so I find this feature an absolute necessity.
A good example of the power of m4 is in building a table of contents in a big page. This involves repeating the heading title in the table of contents and then in the text itself. This is tedious and error-prone, especially when you change the titles. There are specialised tools for generating a table of contents from HTML pages, but the simple facility provided by m4 is irresistible to me.
The following example is a fairly simple-minded table of contents generator. First, create some useful macros in stdlib.m4:
m4_define(`_LINK_TO_LABEL', <A HREF="#$1">$1</A>) m4_define(`_SECTION_HEADER', <A NAME="$1"><H2>$1</H2></A>)
Then define all the section headings in a table at the start of the page body:
m4_define(`_DIFFICULTIES', `The difficulties of HTML') m4_define(`_USING_M4', `Using <EM>m4</EM>') m4_define(`_SHARING', `Sharing HTML Elements Across Several Pages')Then build the table:
<UL><P> <LI> _LINK_TO_LABEL(_DIFFICULTIES) <LI> _LINK_TO_LABEL(_USING_M4) <LI> _LINK_TO_LABEL(_SHARING) <UL>Finally, write the text:
... _SECTION_HEADER(_DIFFICULTIES) ...The advantages of this approach are twofold. If you change your headings you only need to change them in one place, and the table of contents is then automatically regenerated. Also, the links are guaranteed to work.
The table of contents generator that I normally use is a bit more complex and requires a bit more study, but it is much easier to use. It not only builds the table, but it also automatically numbers the headings on the fly—up to four levels of numbering (e.g., section 18.104.22.168), although this can be easily extended. It is very simple to use as follows:
Where you want the table to appear, call Start_TOC.
At every heading use _H1(`Heading for level 1') or _H2(`Heading for level 2') as appropriate.
After the last line of HTML code (probably </HTML>), call End_TOC.
The code for these macros is shown in Listing 1. One restriction is that you should not use diversions (i.e., m4-divert) within your text, unless you preserve the diversion to file 1 used by this TOC generator.
Other than Tables of Contents, many browsers support tabular information. Here are some funky macros as a short cut to producing these tables. First, an example (see Figure 1) of their use:
<CENTER> _Start_Table(BORDER=5) _Table_Hdr(,Apples, Oranges, Lemons) _Table_Row(England, 100,250,300) _Table_Row(France,200,500,100) _Table_Row(Germany,500,50,90) _Table_Row(Spain,,23,2444) _Table_Row(Danmark,,,20) _End_Table </CENTER>
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
Free to Linux Journal readers.Register Now!
- SUSE LLC's SUSE Manager
- My +1 Sword of Productivity
- Managing Linux Using Puppet
- Murat Yener and Onur Dundar's Expert Android Studio (Wrox)
- Non-Linux FOSS: Caffeine!
- Tech Tip: Really Simple HTTP Server with Python
- Doing for User Space What We Did for Kernel Space
- Rogue Wave Software's Zend Server
- Parsing an RSS News Feed with a Bash Script
- SuperTuxKart 0.9.2 Released
With all the industry talk about the benefits of Linux on Power and all the performance advantages offered by its open architecture, you may be considering a move in that direction. If you are thinking about analytics, big data and cloud computing, you would be right to evaluate Power. The idea of using commodity x86 hardware and replacing it every three years is an outdated cost model. It doesn’t consider the total cost of ownership, and it doesn’t consider the advantage of real processing power, high-availability and multithreading like a demon.
This ebook takes a look at some of the practical applications of the Linux on Power platform and ways you might bring all the performance power of this open architecture to bear for your organization. There are no smoke and mirrors here—just hard, cold, empirical evidence provided by independent sources. I also consider some innovative ways Linux on Power will be used in the future.Get the Guide