Advanced Programming in the UNIX Environment docx

Chapter 1. UNIX System Overview Section 1.1. Introduction Section 1.2. UNIX Architecture Section 1.3. Logging In Section 1.4. Files and Directories Section 1.5. Input and Output Section 1.6. Programs and Processes Section 1.7. Error Handling Section 1.8. User Identification Section 1.9. Signals Section 1.10. Time Values Section 1.11. System Calls and Library Functions Section 1.12. Summary Chapter 2. UNIX Standardization and Implementations Section 2.1. Introduction Section 2.2. UNIX Standardization Section 2.3. UNIX System Implementations Section 2.4. Relationship of Standards and Implementations Section 2.5. Limits Section 2.6. Options Section 2.7. Feature Test Macros Section 2.8. Primitive System Data Types Section 2.9. Conflicts Between Standards Section 2.10. Summary Chapter 3. File I/O Section 3.1. Introduction Section 3.2. File Descriptors Section 3.3. open Function Section 3.4. creat Function Section 3.5. close Function Section 3.6. lseek Function Section 3.7. read Function Section 3.8. write Function Section 3.9. I/O Efficiency Section 3.10. File Sharing Section 3.11. Atomic Operations Section 3.12. dup and dup2 Functions Section 3.13. sync, fsync, and fdatasync Functions Section 3.14. fcntl Function Section 3.15. ioctl Function Section 3.16. /dev/fd Section 3.17. Summary Chapter 4. Files and Directories Section 4.1. Introduction Section 4.2. stat, fstat, and lstat Functions Section 4.3. File Types Section 4.4. Set-User-ID and Set-Group-ID Section 4.5. File Access Permissions Section 4.6. Ownership of New Files and Directories Section 4.7. access Function Section 4.8. umask Function Section 4.9. chmod and fchmod Functions Section 4.10. Sticky Bit Section 4.11. chown, fchown, and lchown Functions Section 4.12. File Size Section 4.13. File Truncation Section 4.14. File Systems Section 4.15. link, unlink, remove, and rename Functions Section 4.16. Symbolic Links Section 4.17. symlink and readlink Functions Section 4.18. File Times Section 4.19. utime Function Section 4.20. mkdir and rmdir Functions Section 4.21. Reading Directories Section 4.22. chdir, fchdir, and getcwd Functions Section 4.23. Device Special Files Section 4.24. Summary of File Access Permission Bits Section 4.25. Summary Chapter 5. Standard I/O Library Section 5.1. Introduction Section 5.2. Streams and FILE Objects Section 5.3. Standard Input, Standard Output, and Standard Error Section 5.4. Buffering Section 5.5. Opening a Stream Section 5.6. Reading and Writing a Stream Section 5.7. Line-at-a-Time I/O Section 5.8. Standard I/O Efficiency Section 5.9. Binary I/O Section 5.10. Positioning a Stream Section 5.11. Formatted I/O Section 5.12. Implementation Details Section 5.13. Temporary Files Section 5.14. Alternatives to Standard I/O Section 5.15. Summary Chapter 6. System Data Files and Information Section 6.1. Introduction Section 6.2. Password File Section 6.3. Shadow Passwords Section 6.4. Group File Section 6.5. Supplementary Group IDs Section 6.6. Implementation Differences Section 6.7. Other Data Files Section 6.8. Login Accounting Section 6.9. System Identification Section 6.10. Time and Date Routines Section 6.11. Summary Chapter 7. Process Environment Section 7.1. Introduction Section 7.2. main Function Section 7.3. Process Termination Section 7.4. Command-Line Arguments Section 7.5. Environment List Section 7.6. Memory Layout of a C Program Section 7.7. Shared Libraries Section 7.8. Memory Allocation Section 7.9. Environment Variables Section 7.10. setjmp and longjmp Functions Section 7.11. getrlimit and setrlimit Functions Section 7.12. Summary Chapter 8. Process Control Section 8.1. Introduction Section 8.2. Process Identifiers Section 8.3. fork Function Section 8.4. vfork Function Section 8.5. exit Functions Section 8.6. wait and waitpid Functions Section 8.7. waitid Function Section 8.8. wait3 and wait4 Functions Section 8.9. Race Conditions Section 8.10. exec Functions Section 8.11. Changing User IDs and Group IDs Section 8.12. Interpreter Files Section 8.13. system Function Section 8.14. Process Accounting Section 8.15. User Identification Section 8.16. Process Times Section 8.17. Summary Chapter 9. Process Relationships Section 9.1. Introduction Section 9.2. Terminal Logins Section 9.3. Network Logins Section 9.4. Process Groups Section 9.5. Sessions Section 9.6. Controlling Terminal Section 9.7. tcgetpgrp, tcsetpgrp, and tcgetsid Functions Section 9.8. Job Control Section 9.9. Shell Execution of Programs Section 9.10. Orphaned Process Groups Section 9.11. FreeBSD Implementation Section 9.12. Summary Chapter 10. Signals Section 10.1. Introduction Section 10.2. Signal Concepts Section 10.3. signal Function Section 10.4. Unreliable Signals Section 10.5. Interrupted System Calls Section 10.6. Reentrant Functions Section 10.7. SIGCLD Semantics Section 10.8. Reliable-Signal Terminology and Semantics Section 10.9. kill and raise Functions Section 10.10. alarm and pause Functions Section 10.11. Signal Sets Section 10.12. sigprocmask Function Section 10.13. sigpending Function Section 10.14. sigaction Function Section 10.15. sigsetjmp and siglongjmp Functions Section 10.16. sigsuspend Function Section 10.17. abort Function Section 10.18. system Function Section 10.19. sleep Function Section 10.20. Job-Control Signals Section 10.21. Additional Features Section 10.22. Summary Chapter 11. Threads Section 11.1. Introduction Section 11.2. Thread Concepts Section 11.3. Thread Identification Section 11.4. Thread Creation Section 11.5. Thread Termination Section 11.6. Thread Synchronization Section 11.7. Summary Chapter 12. Thread Control Section 12.1. Introduction Section 12.2. Thread Limits Section 12.3. Thread Attributes Section 12.4. Synchronization Attributes Section 12.5. Reentrancy Section 12.6. Thread-Specific Data Section 12.7. Cancel Options Section 12.8. Threads and Signals Section 12.9. Threads and fork Section 12.10. Threads and I/O Section 12.11. Summary Chapter 13. Daemon Processes Section 13.1. Introduction Section 13.2. Daemon Characteristics Section 13.3. Coding Rules Section 13.4. Error Logging Section 13.5. Single-Instance Daemons Section 13.6. Daemon Conventions Section 13.7. Client–Server Model Section 13.8. Summary Chapter 14. Advanced I/O Section 14.1. Introduction Section 14.2. Nonblocking I/O Section 14.3. Record Locking Section 14.4. STREAMS Section 14.5. I/O Multiplexing Section 14.6. Asynchronous I/O Section 14.7. readv and writev Functions Section 14.8. readn and writen Functions Section 14.9. Memory-Mapped I/O Section 14.10. Summary Chapter 15. Interprocess Communication Section 15.1. Introduction Section 15.2. Pipes Section 15.3. popen and pclose Functions Section 15.4. Coprocesses Section 15.5. FIFOs Section 15.6. XSI IPC Section 15.7. Message Queues Section 15.8. Semaphores Section 15.9. Shared Memory Section 15.10. Client–Server Properties Section 15.11. Summary Chapter 16. Network IPC: Sockets Section 16.1. Introduction Section 16.2. Socket Descriptors Section 16.3. Addressing Section 16.4. Connection Establishment Section 16.5. Data Transfer Section 16.6. Socket Options Section 16.7. Out-of-Band Data Section 16.8. Nonblocking and Asynchronous I/O Section 16.9. Summary Chapter 17. Advanced IPC Section 17.1. Introduction Section 17.2. STREAMS-Based Pipes Section 17.3. UNIX Domain Sockets Section 17.4. Passing File Descriptors Section 17.5. An Open Server, Version 1 Section 17.6. An Open Server, Version 2 Section 17.7. Summary Chapter 18. Terminal I/O Section 18.1. Introduction Section 18.2. Overview Section 18.3. Special Input Characters Section 18.4. Getting and Setting Terminal Attributes Section 18.5. Terminal Option Flags Section 18.6. stty Command Section 18.7. Baud Rate Functions Section 18.8. Line Control Functions Section 18.9. Terminal Identification Section 18.10. Canonical Mode Section 18.11. Noncanonical Mode Section 18.12. Terminal Window Size Section 18.13. termcap, terminfo, and curses Section 18.14. Summary Chapter 19. Pseudo Terminals Section 19.1. Introduction Section 19.2. Overview Section 19.3. Opening Pseudo-Terminal Devices Section 19.4. pty_fork Function Section 19.5. pty Program Section 19.6. Using the pty Program Section 19.7. Advanced Features Section 19.8. Summary Chapter 20. A Database Library Section 20.1. Introduction Section 20.2. History Section 20.3. The Library Section 20.4. Implementation Overview Section 20.5. Centralized or Decentralized? Section 20.6. Concurrency Section 20.7. Building the Library Section 20.8. Source Code Section 20.9. Performance Section 20.10. Summary Chapter 21. Communicating with a Network Printer Section 21.1. Introduction Section 21.2. The Internet Printing Protocol Section 21.3. The Hypertext Transfer Protocol Section 21.4. Printer Spooling Section 21.5. Source Code Section 21.6. Summary Appendix A Appendix B Chapter 1. UNIX System Overview Section 1.1. Introduction Section 1.2. UNIX Architecture Section 1.3. Logging In Section 1.4. Files and Directories Section 1.5. Input and Output Section 1.6. Programs and Processes Section 1.7. Error Handling Section 1.8. User Identification Section 1.9. Signals Section 1.10. Time Values Section 1.11. System Calls and Library Functions Section 1.12. Summary 1.1. Introduction All operating systems provide services for programs they run. Typical services include executing a new program, opening a file, reading a file, allocating a region of memory, getting the current time of day, and so on. The focus of this text is to describe the services provided by various versions of the UNIX operating system. Describing the UNIX System in a strictly linear fashion, without any forward references to terms that haven't been described yet, is nearly impossible (and would probably be boring). This chapter provides a whirlwind tour of the UNIX System from a programmer's perspective. We'll give some brief descriptions and examples of terms and concepts that appear throughout the text. We describe these features in much more detail in later chapters. This chapter also provides an introduction and overview of the services provided by the UNIX System, for programmers new to this environment. 1.2. UNIX Architecture In a strict sense, an operating system can be defined as the software that controls the hardware resources of the computer and provides an environment under which programs can run. Generally, we call this software the kernel, since it is relatively small and resides at the core of the environment. Figure 1.1 shows a diagram of the UNIX System architecture. Figure 1.1. Architecture of the UNIX operating system The interface to the kernel is a layer of software called the system calls (the shaded portion in Figure 1.1). Libraries of common functions are built on top of the system call interface, but applications are free to use both. (We talk more about system calls and library functions in Section 1.11.) The shell is a special application that provides an interface for running other applications. In a broad sense, an operating system is the kernel and all the other software that makes a computer useful and gives the computer its personality. This other software includes system utilities, applications, shells, libraries of common functions, and so on. For example, Linux is the kernel used by the GNU operating system. Some people refer to this as the GNU/Linux operating system, but it is more commonly referred to as simply Linux. Although this usage may not be correct in a strict sense, it is understandable, given the dual meaning of the phrase operating system. (It also has the advantage of being more succinct.) [...]... The ls -l command, for example, prints the login name of the owner of a file, using the password file to map the numeric user ID into the corresponding login name Early UNIX systems used 16-bit integers to represent user and group IDs Contemporary UNIX systems use 32bit integers Example The program in Figure 1.9 prints the user ID and the group ID We call the functions getuid and getgid to return the. .. press the interrupt key, the process terminates because the default action for this signal, named SIGINT, is to terminate the process The process hasn't told the kernel to do anything other than the default with this signal, so the process terminates To catch this signal, the program needs to call the signal function, specifying the name of the function to call when the SIGINT signal is generated The. .. named sig_int; when it's called, it just prints a message and a new prompt Adding 11 lines to the program in Figure 1.7 gives us the version in Figure 1.10 (The 11 new lines are indicated with a plus sign at the beginning of the line.) In Chapter 10, we'll take a long look at signals, as most nontrivial applications deal with them Figure 1.10 Read commands from standard input and execute them #include... system to invoke a system call This differs from many older operating systems, which traditionally defined the kernel entry points in the assembler language of the machine The technique used on UNIX systems is for each system call to have a function of the same name in the standard C library The user process calls this function, using the standard C calling sequence This function then invokes the appropriate... is in Appendix B The declaration of the main function uses the style supported by the ISO C standard (We'll have more to say about the ISO C standard in the next chapter.) We take an argument from the command line, argv[1], as the name of the directory to list In Chapter 7, we'll look at how the main function is called and how the command-line arguments and environment variables are accessible to the. .. having to worry about choosing optimal buffer sizes, such as the BUFFSIZE constant in Figure 1.4 Another advantage of using the standard I/O functions is that they simplify dealing with lines of input (a common occurrence in UNIX applications) The fgets function, for example, reads an entire line The read function, on the other hand, reads a specified number of bytes As we shall see in Section 5.4, the. .. structure of information describing the attributes of the file The attributes of a file are such things as type of file—regular file, directory the size of the file, the owner of the file, permissions for the file—whether other users may access this file—and when the file was last modified The stat and fstat functions return a structure of information containing all the attributes of a file In Chapter... 2.1 Introduction Much work has gone into standardizing the UNIX programming environment and the C programming language Although applications have always been quite portable across different versions of the UNIX operating system, the proliferation of versions and differences during the 1980s led many large users, such as the U.S government, to call for standardization In this chapter we first look at the. .. to the constant EACCES, this indicates a permission problem, such as insufficient permission to open the requested file On Linux, the error constants are listed in the errno(3) manual page POSIX and ISO C define errno as a symbol expanding into a modifiable lvalue of type integer This can be either an integer that contains the error number or a function that returns a pointer to the error number The. .. a two-byte integer If the full ASCII login name and group name were used instead, additional disk space would be required In addition, comparing strings during permission checks is more expensive than comparing integers Users, however, work better with names than with numbers, so the password file maintains the mapping between login names and user IDs, and the group file provides the mapping between . shell running in one of the windows.) A shell is a command-line interpreter that reads user input and executes commands. The user input to a shell is normally from the terminal (an interactive. meaning of the phrase operating system. (It also has the advantage of being more succinct.) 1.3. Logging In Login Name When we log in to a UNIX system, we enter our login name, followed. of the UNIX System architecture. Figure 1.1. Architecture of the UNIX operating system The interface to the kernel is a layer of software called the system calls (the shaded portion in