In my opinion these are best two books on the subject. Stevens' book is classic and have been updated quite recently (3rd edition came out 3 years ago), LPI is very extensive and have some specific Linux info not present in Stevens' book and is clearly influenced by Stevens book.
How strongly do you recommend these books? Unfortunately I'm a college student without much cash to toss around, but I can scrape together enough for a book if it'll make me a better programmer in the long run.
If you want to learn what's one layer beneath the hood of most higher-level language environments, they are well worth the investment. And IMO this stuff is worth learning. One day, you will be glad to know it when you use strace to successfully debug why your application doesn't work, while the rest of your coworkers tear up more code in befuddlement :-)
I'd recommend this book instead 'The Linux Programming Interface' http://man7.org/tlpi/ it's a lot more recent and the content is excellent, though it's not a free download. The author is also the maintainer of the linux man pages.
Some of the subjects it treats are low-level enough (and of Unix-ish heritage) that their treatment is probably not irrelevant today. The performance considerations of threads and processes are probably out of date, but their API (sections 3 and 4) is largely still the same. Same for shared memory and other IPC mechanisms described in section 5. The API re. section 7 still applies -- /proc has expanded considerably since 2001, but it's still used in the same manner. Chapter 8 is probably more out of date than others, but you can still follow it. Stuff in 9 is probably not used much anymore, an #10, while adequate, would probably be considered incomplete today.
I'd say it's still useful to someone who comes to Linux from other platforms, or to people who are already using Linux but aren't familiar with systems programming under it.
Edit: although, as someone else pointed out, APUE is probably a better choice (and was a better choice back in 2001, too).
If you're looking for a better maintained book, I'd recommend "Advanced Programming in the UNIX Environment" by W. Richard Stevens, revised by Stephen A. Rago.
It's not a free PDF however, but well worth the money.
With the exception of systemd versus init, the big ideas are pretty much unchanged. Details around hardware and distribution features should be kept in historical perspective and application context, by which I mean that a 2001 64 megabytes of RAM desktop might be today's embedded system and most people won't have to configure networking over two dial up modems.
For me, the critical issue with technical books is readability and accessibility. If it's in front of me and I enjoy reading it because I'm learning something, that's often good enough. If I were already an expert Linux programmer, then I might have different criteria. I know I ain't.
This book is dated - there was the kernel 2.4 and a lot of system calls were changed or removed - but I think it is one of the best book available on GNU/Linux system programming.
I love "UNIX Systems Programming: Communication, Concurrency and Threads", it is simply great.
I am getting interested in Unix programming, but essentially starting from scratch. I've read through the first two chapters of the The Linux Programming Interface, and while I think it is a great book, so far it has not been easy for me to find points of entry. I think it might not be the best book for me to start with.
I've just started How Linux Works, but I thought I might take this opportunity to ask for suggestions for someone trying to get started (doesn't have to be a book).
Raymond's The Art of Unix Programming is a good resource for understanding the design philosophy of Unix...and by extension Linux. It explains much of the context and history behind why things are done the way they are done and what good nix programs do to be good nix programs.
It is somewhat helpful, but the examples for shared memory and mmap ignore concurrency issues and refer you to a generic, non-language specific WikiPedia page for guidance.
why are all the chapters in separate pdf's? Is that unintentional or an enticement to buy the book when it comes out? If it's the former, anybody got a full pdf download link?
Book does not understand its audience. "An editor is the program that you use to edit source code." No "advanced" programmer needs to be told that. OK, maybe if all you know is an IDE, you don't know this...but the book says it's assumed that the reader can do basic command-line stuff. If you can do that you must know what an editor is.
Also I saw "GNU/Liux" in the front matter.
[edit] Next section started "A compiler turns human-readable source code into machine-readable object code that can actually run."
I think this was the Windows -> Linux chapter. Almost no one who bought the book needed it but if your prior experience was something like Visual Studio 6.0 (current at that time) it helped to get some pointer. Back then newbies were liable to end up using pico... And that would not go so well.
Yeah, that would be me lol. I've been dodging that program for a long time now. Briefly tolerated it in a self-contained LISP setup. Had a piece of paper helping me along on basic stuff. (shudders)
Using the higher performance Linux specific interfaces like epoll isn't doing it wrong, it is getting the most out of your platform. Perhaps it is doing it wrong to use it directly instead of a library in application code, but someone still has to know enough to write the library.
This sort of comment could be based on real knowledge, but it's hard to tell because you just gave us a conclusion rather than showing us how you came to it. A better comment would add information: give an example or two, tell a story, or say what's behind your thinking somehow.
The Linux Programming Interface: http://www.amazon.com/Linux-Programming-Interface-System-Han...
Advanced Programming in the UNIX Environment: http://www.amazon.com/Advanced-Programming-UNIX-Environment-...
A not-too-distant third choice, Linux System Programming: http://www.amazon.com/Linux-System-Programming-Talking-Direc...