In the late 1990's, Linux began to attract large-scale attention beyond the
relatively small, hacker community which had been working on it for some
time. With all that attention came many new developers who liked what they
saw and wanted to be a part of it. The book that many of those developers
kept next to their keyboard was the classic Linux Application
(LAD), by early Red Hat hackers Michael K. Johnson and Erik
W. Troan. LAD was published in 1998, meaning that, at this point, it is
vastly out of date. The Linux world does not stand still, and does not
make life easy for those who would publish technical reference books.
Trust your editor on this.
So it was a pleasant surprise to see a new edition of LAD show up in the
mail. This core text, it turns out, has not gone out of maintenance after
According to the preface:
You can now browse and search the entire content of this book at http://ladweb.net
to make this book even
more useful to you.
As of this writing, the web site has not caught up with that claim - it
still discusses the first edition (and with no "entire content") to
browse. One assumes that situation will be rectified in time. If the book
is being released under some sort of free license, however, that
is not stated explicitly.
The structure and content of the book has not changed all that much from
the first edition: LAD still concerns itself with low-level Linux
programming, system calls, and some C libraries. The updates are to be
found in the details: the text now matches, for the most part, the
interfaces provided by the 2.6 kernel and glibc 2.3. Some new interfaces
(such as epoll()) have been covered, and there is a new chapter on
security pitfalls and how to avoid them. The discussion of the socket
interface covers IPv6, the regular expression discussion has been expanded,
real-time signals are covered, etc.
With these changes, LAD is, once again, the definitive reference for the
low-level Linux C API. Whether you need to learn about memory allocation
debugging facilities, the details of process management, file descriptor
magic, or more, you're likely to find what you need in this book. Much of
that information is also available in generic Unix texts; the difference is
that LAD looks at exactly what Linux offers. While Linux follows the
relevant standards to a great degree, there are many places where Linux
diverges from the standards or offers extra capabilities. A reference book
which documents the Linux way of doing things is a good thing.
That said, your editor does have some quibbles with the second edition.
One is that the update appears, in many places, to have been done in a
hurry. The LGPL is called the "Library General Public License" - but it
has not had that name for quite a few years now. The recommended system
administration book is Sobel's A Practical Guide to Red Hat
Linux 8. The (new) documentation
of strace claims that it writes to the standard output, which is
not true (it writes to stderr). Passwords, it claims, are usually stored
in /etc/passwd. Many flags to the clone() system call
are missing; a number of mmap() flags are absent as well. Your
editor may have been willing to forgive all of this if the authors, while
being nice enough to mention Linux Device Drivers, had noticed that
a new edition has come out since 1998.
Perhaps more to the point, however, LAD may be falling behind the way that
applications are being developed for Linux. Your editor has certainly done
his time writing ioctl() calls to control TTY parameters - but not
recently. The chapters on virtual consoles and S-Lang seem rather quaint.
While a great deal of Linux software is still developed in C, quite a bit
is not. After reading LAD, one might almost conclude that graphical
applications simply do not exist under Linux. The authors clearly had to
limit their scope, and they cannot be faulted for failing to document, say,
the GNOME and KDE libraries. But the second edition could have been an
ideal vehicle for pointing developers toward the sorts of tools being used
for new code, and away from writing TTY-oriented applications.
That said, application developers still need to understand how to manage
memory, create processes, handle signals, work with files, etc. The second
edition of Linux Application Development fills that need and more;
it is a most welcome update. It will, beyond doubt, find a location very
near the keyboards of a great many Linux application hackers.
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