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A História do comando ping

Colaboração: Rubens Queiroz de Almeida

Data de Publicação: 19 de Novembro de 2004

O comando ping, que todos nós conhecemos e usamos muito, foi escrito por Michael John Muss.

O autor descreve em detalhes como teve a idéia de escrever o programa ping em uma noite de trabalho.

Um fato interessante é que um visitante da Amazon, visitando o site de compras, descobriu um livro chamado The History of Ping, uma história infantil que contava a história de um patinho. Este leitor escreveu uma resenha no site da Amazon dizendo que o livro era uma explicação brilhante e intuitiva de um dos comandos mais veneráveis do sistema Unix. Na mesma página encontra-se também o comentário de uma pessoa que comprou o livro pensando se tratar de um livro sobre tecnologia.

Reproduzo a seguir, em inglês, o texto da resenha e os comentários da leitora enganada.

Customer Comments

A reader from Upper Volta, Uzbekistan, March 7, 1999

Excellent, heart-warming tale of exploration and discovery. Using deft allegory, the authors have provided an insightful and intuitive explanation of one of Unix's most venerable networking utilities. Even more stunning is that they were clearly working with a very early beta of the program, as their book first appeared in 1933, years (decades!) before the operating system and network infrastructure were finalized.

The book describes networking in terms even a child could understand, choosing to anthropomorphize the underlying packet structure. The ping packet is described as a duck, who, with other packets (more ducks), spends a certain period of time on the host machine (the wise-eyed boat). At the same time each day (I suspect this is scheduled under cron), the little packets (ducks) exit the host (boat) by way of a bridge (a bridge). From the bridge, the packets travel onto the internet (here embodied by the Yangtze River).

The title character -- er, packet, is called Ping. Ping meanders around the river before being received by another host (another boat). He spends a brief time on the other boat, but eventually returns to his original host machine (the wise-eyed boat) somewhat the worse for wear.

The book avoids many of the cliches one might expect. For example, with a story set on a river, the authors might have sunk to using that tired old plot device: the flood ping. The authors deftly avoid this.

Who Should Buy This Book

If you need a good, high-level overview of the ping utility, this is the book. I can't recommend it for most managers, as the technical aspects may be too overwhelming and the basic concepts too daunting.

Problems With This Book

As good as it is, The Story About Ping is not without its faults. There is no index, and though the ping(8) man pages cover the command line options well enough, some review of them seems to be in order. Likewise, in a book solely about Ping, I would have expected a more detailed overview of the ICMP packet structure.

But even with these problems, The Story About Ping has earned a place on my bookshelf, right between Stevens' Advanced Programming in the Unix Environment, and my dog-eared copy of Dante's seminal work on MS Windows, Inferno. Who can read that passage on the Windows API ("Obscure, profound it was, and nebulous, So that by fixing on its depths my sight -- Nothing whatever I discerned therein."), without shaking their head with deep understanding. But I digress.

Melissa Rondeau from Braintree, MA , March 11, 1999

I collect reference books about the UNIX operating system. PING (short for Packet InterNet Groper) has always been one of those UNIX commands whose usefulness transcends its own simplicity. A coworker told me about a book dedicated to this one command, "The Story About PING." I was a little surprised that an entire book was devoted to the history of this UNIX command, but the price was certainly affordable, so I ordered it from a distributor. What arrived was actually an illustrated story book for young children. I thought it was a mistake, but my coworker told me later he was just playing a prank. I did read the book on the plane while traveling on business, and I have to admit, it's one of the finest pieces of children's literature I have ever read. A classic tale of adventure and innocence, with an important lesson to be learned. Not what I originally expected, but an enjoyable read none the less.