Table of Contents

• Main Menu
• 1 Introduction
  • 1.1 Getting Started
  • 1.2 Standards and Portability
    • 1.2.1 ISO C
    • 1.2.2 POSIX (The Portable Operating System Interface)
    • 1.2.3 Berkeley Unix
    • 1.2.4 SVID (The System V Interface Description)
    • 1.2.5 XPG (The X/Open Portability Guide)
  • 1.3 Using the Library
    • 1.3.1 Header Files
    • 1.3.2 Macro Definitions of Functions
    • 1.3.3 Reserved Names
    • 1.3.4 Feature Test Macros
  • 1.4 Roadmap to the Manual
• 2 Error Reporting
  • 2.1 Checking for Errors
  • 2.2 Error Codes
  • 2.3 Error Messages
• 3 Virtual Memory Allocation And Paging
  • 3.1 Process Memory Concepts
  • 3.2 Allocating Storage For Program Data
    • 3.2.1 Memory Allocation in C Programs
      • 3.2.1.1 Dynamic Memory Allocation
    • 3.2.2 Unconstrained Allocation
      • 3.2.2.1 Basic Memory Allocation
      • 3.2.2.2 Examples of malloc
      • 3.2.2.3 Freeing Memory Allocated with malloc
      • 3.2.2.4 Changing the Size of a Block
      • 3.2.2.5 Allocating Cleared Space
      • 3.2.2.6 Efficiency Considerations for malloc
      • 3.2.2.7 Allocating Aligned Memory Blocks
      • 3.2.2.8 Malloc Tunable Parameters
      • 3.2.2.9 Heap Consistency Checking
      • 3.2.2.10 Memory Allocation Hooks
      • 3.2.2.11 Statistics for Memory Allocation with malloc
      • 3.2.2.12 Summary of malloc-Related Functions
    • 3.2.3 Allocation Debugging
      • 3.2.3.1 How to install the tracing functionality
      • 3.2.3.2 Example program excerpts
      • 3.2.3.3 Some more or less clever ideas
      • 3.2.3.4 Interpreting the traces
    • 3.2.4 Obstacks
      • 3.2.4.1 Creating Obstacks
      • 3.2.4.2 Preparing for Using Obstacks
      • 3.2.4.3 Allocation in an Obstack
      • 3.2.4.4 Freeing Objects in an Obstack
      • 3.2.4.5 Obstack Functions and Macros
      • 3.2.4.6 Growing Objects
      • 3.2.4.7 Extra Fast Growing Objects
      • 3.2.4.8 Status of an Obstack
      • 3.2.4.9 Alignment of Data in Obstacks
      • 3.2.4.10 Obstack Chunks
      • 3.2.4.11 Summary of Obstack Functions
    • 3.2.5 Automatic Storage with Variable Size
      • 3.2.5.1 alloca Example
      • 3.2.5.2 Advantages of alloca
      • 3.2.5.3 Disadvantages of alloca
      • 3.2.5.4 GNU C Variable-Size Arrays
  • 3.3 Resizing the Data Segment
  • 3.4 Locking Pages
    • 3.4.1 Why Lock Pages
    • 3.4.2 Locked Memory Details
    • 3.4.3 Functions To Lock And Unlock Pages
• 4 Character Handling
  • 4.1 Classification of Characters
  • 4.2 Case Conversion
  • 4.3 Character class determination for wide characters
  • 4.4 Notes on using the wide character classes
  • 4.5 Mapping of wide characters.
• 5 String and Array Utilities
  • 5.1 Representation of Strings
  • 5.2 String and Array Conventions
  • 5.3 String Length
  • 5.4 Copying and Concatenation
  • 5.5 String/Array Comparison
  • 5.6 Collation Functions
  • 5.7 Search Functions
    • 5.7.1 Compatibility String Search Functions
  • 5.8 Finding Tokens in a String
  • 5.9 strfry
  • 5.10 Trivial Encryption
  • 5.11 Encode Binary Data
  • 5.12 Argz and Envz Vectors
    • 5.12.1 Argz Functions
    • 5.12.2 Envz Functions
• 6 Character Set Handling
  • 6.1 Introduction to Extended Characters
  • 6.2 Overview about Character Handling Functions
  • 6.3 Restartable Multibyte Conversion Functions
    • 6.3.1 Selecting the conversion and its properties
    • 6.3.2 Representing the state of the conversion
    • 6.3.3 Converting Single Characters
    • 6.3.4 Converting Multibyte and Wide Character Strings
    • 6.3.5 A Complete Multibyte Conversion Example
  • 6.4 Non-reentrant Conversion Function
    • 6.4.1 Non-reentrant Conversion of Single Characters
    • 6.4.2 Non-reentrant Conversion of Strings
    • 6.4.3 States in Non-reentrant Functions
  • 6.5 Generic Charset Conversion
    • 6.5.1 Generic Character Set Conversion Interface
    • 6.5.2 A complete iconv example
    • 6.5.3 Some Details about other iconv Implementations
    • 6.5.4 The iconv Implementation in the GNU C library
      • 6.5.4.1 Format of gconv-modules files
      • 6.5.4.2 Finding the conversion path in iconv
      • 6.5.4.3 iconv module data structures
      • 6.5.4.4 iconv module interfaces
• 7 Locales and Internationalization
  • 7.1 What Effects a Locale Has
  • 7.2 Choosing a Locale
  • 7.3 Categories of Activities that Locales Affect
  • 7.4 How Programs Set the Locale
  • 7.5 Standard Locales
  • 7.6 Accessing Locale Information
    • 7.6.1 localeconv: It is portable but ...
      • 7.6.1.1 Generic Numeric Formatting Parameters
      • 7.6.1.2 Printing the Currency Symbol
      • 7.6.1.3 Printing the Sign of a Monetary Amount
    • 7.6.2 Pinpoint Access to Locale Data
  • 7.7 A dedicated function to format numbers
  • 7.8 Yes-or-No Questions
• 8 Message Translation
  • 8.1 X/Open Message Catalog Handling
    • 8.1.1 The catgets function family
    • 8.1.2 Format of the message catalog files
    • 8.1.3 Generate Message Catalogs files
    • 8.1.4 How to use the catgets interface
      • 8.1.4.1 Not using symbolic names
      • 8.1.4.2 Using symbolic names
      • 8.1.4.3 How does to this allow to develop
  • 8.2 The Uniforum approach to Message Translation
    • 8.2.1 The gettext family of functions
      • 8.2.1.1 What has to be done to translate a message?
      • 8.2.1.2 How to determine which catalog to be used
      • 8.2.1.3 Additional functions for more complicated situations
      • 8.2.1.4 How to specify the output character set gettext uses
      • 8.2.1.5 How to use gettext in GUI programs
      • 8.2.1.6 User influence on gettext
    • 8.2.2 Programs to handle message catalogs for gettext
• 9 Searching and Sorting
  • 9.1 Defining the Comparison Function
  • 9.2 Array Search Function
  • 9.3 Array Sort Function
  • 9.4 Searching and Sorting Example
  • 9.5 The hsearch function.
  • 9.6 The tsearch function.
• 10 Pattern Matching
  • 10.1 Wildcard Matching
  • 10.2 Globbing
    • 10.2.1 Calling glob
    • 10.2.2 Flags for Globbing
    • 10.2.3 More Flags for Globbing
  • 10.3 Regular Expression Matching
    • 10.3.1 POSIX Regular Expression Compilation
    • 10.3.2 Flags for POSIX Regular Expressions
    • 10.3.3 Matching a Compiled POSIX Regular Expression
    • 10.3.4 Match Results with Subexpressions
    • 10.3.5 Complications in Subexpression Matching
    • 10.3.6 POSIX Regexp Matching Cleanup
  • 10.4 Shell-Style Word Expansion
    • 10.4.1 The Stages of Word Expansion
    • 10.4.2 Calling wordexp
    • 10.4.3 Flags for Word Expansion
    • 10.4.4 wordexp Example
    • 10.4.5 Details of Tilde Expansion
    • 10.4.6 Details of Variable Substitution
• 11 Input/Output Overview
  • 11.1 Input/Output Concepts
    • 11.1.1 Streams and File Descriptors
    • 11.1.2 File Position
  • 11.2 File Names
    • 11.2.1 Directories
    • 11.2.2 File Name Resolution
    • 11.2.3 File Name Errors
    • 11.2.4 Portability of File Names
• 12 Input/Output on Streams
  • 12.1 Streams
  • 12.2 Standard Streams
  • 12.3 Opening Streams
  • 12.4 Closing Streams
  • 12.5 Streams and Threads
  • 12.6 Streams in Internationalized Applications
  • 12.7 Simple Output by Characters or Lines
  • 12.8 Character Input
  • 12.9 Line-Oriented Input
  • 12.10 Unreading
    • 12.10.1 What Unreading Means
    • 12.10.2 Using ungetc To Do Unreading
  • 12.11 Block Input/Output
  • 12.12 Formatted Output
    • 12.12.1 Formatted Output Basics
    • 12.12.2 Output Conversion Syntax
    • 12.12.3 Table of Output Conversions
    • 12.12.4 Integer Conversions
    • 12.12.5 Floating-Point Conversions
    • 12.12.6 Other Output Conversions
    • 12.12.7 Formatted Output Functions
    • 12.12.8 Dynamically Allocating Formatted Output
    • 12.12.9 Variable Arguments Output Functions
    • 12.12.10 Parsing a Template String
    • 12.12.11 Example of Parsing a Template String
  • 12.13 Customizing printf
    • 12.13.1 Registering New Conversions
    • 12.13.2 Conversion Specifier Options
    • 12.13.3 Defining the Output Handler
    • 12.13.4 printf Extension Example
    • 12.13.5 Predefined printf Handlers
  • 12.14 Formatted Input
    • 12.14.1 Formatted Input Basics
    • 12.14.2 Input Conversion Syntax
    • 12.14.3 Table of Input Conversions
    • 12.14.4 Numeric Input Conversions
    • 12.14.5 String Input Conversions
    • 12.14.6 Dynamically Allocating String Conversions
    • 12.14.7 Other Input Conversions
    • 12.14.8 Formatted Input Functions
    • 12.14.9 Variable Arguments Input Functions
  • 12.15 End-Of-File and Errors
  • 12.16 Recovering from errors
  • 12.17 Text and Binary Streams
  • 12.18 File Positioning
  • 12.19 Portable File-Position Functions
  • 12.20 Stream Buffering
    • 12.20.1 Buffering Concepts
    • 12.20.2 Flushing Buffers
    • 12.20.3 Controlling Which Kind of Buffering
  • 12.21 Other Kinds of Streams
    • 12.21.1 String Streams
    • 12.21.2 Obstack Streams
    • 12.21.3 Programming Your Own Custom Streams
      • 12.21.3.1 Custom Streams and Cookies
      • 12.21.3.2 Custom Stream Hook Functions
  • 12.22 Formatted Messages
    • 12.22.1 Printing Formatted Messages
    • 12.22.2 Adding Severity Classes
    • 12.22.3 How to use fmtmsg and addseverity
• 13 Low-Level Input/Output
  • 13.1 Opening and Closing Files
  • 13.2 Input and Output Primitives
  • 13.3 Setting the File Position of a Descriptor
  • 13.4 Descriptors and Streams
  • 13.5 Dangers of Mixing Streams and Descriptors
    • 13.5.1 Linked Channels
    • 13.5.2 Independent Channels
    • 13.5.3 Cleaning Streams
  • 13.6 Fast Scatter-Gather I/O
  • 13.7 Memory-mapped I/O
  • 13.8 Waiting for Input or Output
  • 13.9 Synchronizing I/O operations
  • 13.10 Perform I/O Operations in Parallel
    • 13.10.1 Asynchronous Read and Write Operations
    • 13.10.2 Getting the Status of AIO Operations
    • 13.10.3 Getting into a Consistent State
    • 13.10.4 Cancellation of AIO Operations
    • 13.10.5 How to optimize the AIO implementation
  • 13.11 Control Operations on Files
  • 13.12 Duplicating Descriptors
  • 13.13 File Descriptor Flags
  • 13.14 File Status Flags
    • 13.14.1 File Access Modes
    • 13.14.2 Open-time Flags
    • 13.14.3 I/O Operating Modes
    • 13.14.4 Getting and Setting File Status Flags
  • 13.15 File Locks
  • 13.16 Interrupt-Driven Input
  • 13.17 Generic I/O Control operations
• 14 File System Interface
  • 14.1 Working Directory
  • 14.2 Accessing Directories
    • 14.2.1 Format of a Directory Entry
    • 14.2.2 Opening a Directory Stream
    • 14.2.3 Reading and Closing a Directory Stream
    • 14.2.4 Simple Program to List a Directory
    • 14.2.5 Random Access in a Directory Stream
    • 14.2.6 Scanning the Content of a Directory
    • 14.2.7 Simple Program to List a Directory, Mark II
  • 14.3 Working with Directory Trees
  • 14.4 Hard Links
  • 14.5 Symbolic Links
  • 14.6 Deleting Files
  • 14.7 Renaming Files
  • 14.8 Creating Directories
  • 14.9 File Attributes
    • 14.9.1 The meaning of the File Attributes
    • 14.9.2 Reading the Attributes of a File
    • 14.9.3 Testing the Type of a File
    • 14.9.4 File Owner
    • 14.9.5 The Mode Bits for Access Permission
    • 14.9.6 How Your Access to a File is Decided
    • 14.9.7 Assigning File Permissions
    • 14.9.8 Testing Permission to Access a File
    • 14.9.9 File Times
    • 14.9.10 File Size
  • 14.10 Making Special Files
  • 14.11 Temporary Files
• 15 Pipes and FIFOs
  • 15.1 Creating a Pipe
  • 15.2 Pipe to a Subprocess
  • 15.3 FIFO Special Files
  • 15.4 Atomicity of Pipe I/O
• 16 Sockets
  • 16.1 Socket Concepts
  • 16.2 Communication Styles
  • 16.3 Socket Addresses
    • 16.3.1 Address Formats
    • 16.3.2 Setting the Address of a Socket
    • 16.3.3 Reading the Address of a Socket
  • 16.4 Interface Naming
  • 16.5 The Local Namespace
    • 16.5.1 Local Namespace Concepts
    • 16.5.2 Details of Local Namespace
    • 16.5.3 Example of Local-Namespace Sockets
  • 16.6 The Internet Namespace
    • 16.6.1 Internet Socket Address Formats
    • 16.6.2 Host Addresses
      • 16.6.2.1 Internet Host Addresses
      • 16.6.2.2 Host Address Data Type
      • 16.6.2.3 Host Address Functions
      • 16.6.2.4 Host Names
    • 16.6.3 Internet Ports
    • 16.6.4 The Services Database
    • 16.6.5 Byte Order Conversion
    • 16.6.6 Protocols Database
    • 16.6.7 Internet Socket Example
  • 16.7 Other Namespaces
  • 16.8 Opening and Closing Sockets
    • 16.8.1 Creating a Socket
    • 16.8.2 Closing a Socket
    • 16.8.3 Socket Pairs
  • 16.9 Using Sockets with Connections
    • 16.9.1 Making a Connection
    • 16.9.2 Listening for Connections
    • 16.9.3 Accepting Connections
    • 16.9.4 Who is Connected to Me?
    • 16.9.5 Transferring Data
      • 16.9.5.1 Sending Data
      • 16.9.5.2 Receiving Data
      • 16.9.5.3 Socket Data Options
    • 16.9.6 Byte Stream Socket Example
    • 16.9.7 Byte Stream Connection Server Example
    • 16.9.8 Out-of-Band Data
  • 16.10 Datagram Socket Operations
    • 16.10.1 Sending Datagrams
    • 16.10.2 Receiving Datagrams
    • 16.10.3 Datagram Socket Example
    • 16.10.4 Example of Reading Datagrams
  • 16.11 The inetd Daemon
    • 16.11.1 inetd Servers
    • 16.11.2 Configuring inetd
  • 16.12 Socket Options
    • 16.12.1 Socket Option Functions
    • 16.12.2 Socket-Level Options
  • 16.13 Networks Database
• 17 Low-Level Terminal Interface
  • 17.1 Identifying Terminals
  • 17.2 I/O Queues
  • 17.3 Two Styles of Input: Canonical or Not
  • 17.4 Terminal Modes
    • 17.4.1 Terminal Mode Data Types
    • 17.4.2 Terminal Mode Functions
    • 17.4.3 Setting Terminal Modes Properly
    • 17.4.4 Input Modes
    • 17.4.5 Output Modes
    • 17.4.6 Control Modes
    • 17.4.7 Local Modes
    • 17.4.8 Line Speed
    • 17.4.9 Special Characters
      • 17.4.9.1 Characters for Input Editing
      • 17.4.9.2 Characters that Cause Signals
      • 17.4.9.3 Special Characters for Flow Control
      • 17.4.9.4 Other Special Characters
    • 17.4.10 Noncanonical Input
  • 17.5 BSD Terminal Modes
  • 17.6 Line Control Functions
  • 17.7 Noncanonical Mode Example
  • 17.8 Pseudo-Terminals
    • 17.8.1 Allocating Pseudo-Terminals
    • 17.8.2 Opening a Pseudo-Terminal Pair
• 18 Syslog
  • 18.1 Overview of Syslog
  • 18.2 Submitting Syslog Messages
    • 18.2.1 openlog
    • 18.2.2 syslog, vsyslog
    • 18.2.3 closelog
    • 18.2.4 setlogmask
    • 18.2.5 Syslog Example
• 19 Mathematics
  • 19.1 Predefined Mathematical Constants
  • 19.2 Trigonometric Functions
  • 19.3 Inverse Trigonometric Functions
  • 19.4 Exponentiation and Logarithms
  • 19.5 Hyperbolic Functions
  • 19.6 Special Functions
  • 19.7 Known Maximum Errors in Math Functions
  • 19.8 Pseudo-Random Numbers
    • 19.8.1 ISO C Random Number Functions
    • 19.8.2 BSD Random Number Functions
    • 19.8.3 SVID Random Number Function
  • 19.9 Is Fast Code or Small Code preferred?
• 20 Arithmetic Functions
  • 20.1 Integers
  • 20.2 Integer Division
  • 20.3 Floating Point Numbers
  • 20.4 Floating-Point Number Classification Functions
  • 20.5 Errors in Floating-Point Calculations
    • 20.5.1 FP Exceptions
    • 20.5.2 Infinity and NaN
    • 20.5.3 Examining the FPU status word
    • 20.5.4 Error Reporting by Mathematical Functions
  • 20.6 Rounding Modes
  • 20.7 Floating-Point Control Functions
  • 20.8 Arithmetic Functions
    • 20.8.1 Absolute Value
    • 20.8.2 Normalization Functions
    • 20.8.3 Rounding Functions
    • 20.8.4 Remainder Functions
    • 20.8.5 Setting and modifying single bits of FP values
    • 20.8.6 Floating-Point Comparison Functions
    • 20.8.7 Miscellaneous FP arithmetic functions
  • 20.9 Complex Numbers
  • 20.10 Projections, Conjugates, and Decomposing of Complex Numbers
  • 20.11 Parsing of Numbers
    • 20.11.1 Parsing of Integers
    • 20.11.2 Parsing of Floats
  • 20.12 Old-fashioned System V number-to-string functions
• 21 Date and Time
  • 21.1 Time Basics
  • 21.2 Elapsed Time
  • 21.3 Processor And CPU Time
    • 21.3.1 CPU Time Inquiry
    • 21.3.2 Processor Time Inquiry
  • 21.4 Calendar Time
    • 21.4.1 Simple Calendar Time
    • 21.4.2 High-Resolution Calendar
    • 21.4.3 Broken-down Time
    • 21.4.4 High Accuracy Clock
    • 21.4.5 Formatting Calendar Time
    • 21.4.6 Convert textual time and date information back
      • 21.4.6.1 Interpret string according to given format
      • 21.4.6.2 A More User-friendly Way to Parse Times and Dates
    • 21.4.7 Specifying the Time Zone with TZ
    • 21.4.8 Functions and Variables for Time Zones
    • 21.4.9 Time Functions Example
  • 21.5 Setting an Alarm
  • 21.6 Sleeping
• 22 Resource Usage And Limitation
  • 22.1 Resource Usage
  • 22.2 Limiting Resource Usage
  • 22.3 Process CPU Priority And Scheduling
    • 22.3.1 Absolute Priority
      • 22.3.1.1 Using Absolute Priority
    • 22.3.2 Realtime Scheduling
    • 22.3.3 Basic Scheduling Functions
    • 22.3.4 Traditional Scheduling
      • 22.3.4.1 Introduction To Traditional Scheduling
      • 22.3.4.2 Functions For Traditional Scheduling
  • 22.4 Querying memory available resources
    • 22.4.1 Overview about traditional Unix memory handling
    • 22.4.2 How to get information about the memory subsystem?
  • 22.5 Learn about the processors available
• 23 Non-Local Exits
  • 23.1 Introduction to Non-Local Exits
  • 23.2 Details of Non-Local Exits
  • 23.3 Non-Local Exits and Signals
  • 23.4 Complete Context Control
• 24 Signal Handling
  • 24.1 Basic Concepts of Signals
    • 24.1.1 Some Kinds of Signals
    • 24.1.2 Concepts of Signal Generation
    • 24.1.3 How Signals Are Delivered
  • 24.2 Standard Signals
    • 24.2.1 Program Error Signals
    • 24.2.2 Termination Signals
    • 24.2.3 Alarm Signals
    • 24.2.4 Asynchronous I/O Signals
    • 24.2.5 Job Control Signals
    • 24.2.6 Operation Error Signals
    • 24.2.7 Miscellaneous Signals
    • 24.2.8 Signal Messages
  • 24.3 Specifying Signal Actions
    • 24.3.1 Basic Signal Handling
    • 24.3.2 Advanced Signal Handling
    • 24.3.3 Interaction of signal and sigaction
    • 24.3.4 sigaction Function Example
    • 24.3.5 Flags for sigaction
    • 24.3.6 Initial Signal Actions
  • 24.4 Defining Signal Handlers
    • 24.4.1 Signal Handlers that Return
    • 24.4.2 Handlers That Terminate the Process
    • 24.4.3 Nonlocal Control Transfer in Handlers
    • 24.4.4 Signals Arriving While a Handler Runs
    • 24.4.5 Signals Close Together Merge into One
    • 24.4.6 Signal Handling and Nonreentrant Functions
    • 24.4.7 Atomic Data Access and Signal Handling
      • 24.4.7.1 Problems with Non-Atomic Access
      • 24.4.7.2 Atomic Types
      • 24.4.7.3 Atomic Usage Patterns
  • 24.5 Primitives Interrupted by Signals
  • 24.6 Generating Signals
    • 24.6.1 Signaling Yourself
    • 24.6.2 Signaling Another Process
    • 24.6.3 Permission for using kill
    • 24.6.4 Using kill for Communication
  • 24.7 Blocking Signals
    • 24.7.1 Why Blocking Signals is Useful
    • 24.7.2 Signal Sets
    • 24.7.3 Process Signal Mask
    • 24.7.4 Blocking to Test for Delivery of a Signal
    • 24.7.5 Blocking Signals for a Handler
    • 24.7.6 Checking for Pending Signals
    • 24.7.7 Remembering a Signal to Act On Later
  • 24.8 Waiting for a Signal
    • 24.8.1 Using pause
    • 24.8.2 Problems with pause
    • 24.8.3 Using sigsuspend
  • 24.9 Using a Separate Signal Stack
  • 24.10 BSD Signal Handling
    • 24.10.1 BSD Function to Establish a Handler
    • 24.10.2 BSD Functions for Blocking Signals
• 25 The Basic Program/System Interface
  • 25.1 Program Arguments
    • 25.1.1 Program Argument Syntax Conventions
    • 25.1.2 Parsing Program Arguments
  • 25.2 Parsing program options using getopt
    • 25.2.1 Using the getopt function
    • 25.2.2 Example of Parsing Arguments with getopt
    • 25.2.3 Parsing Long Options with getopt_long
    • 25.2.4 Example of Parsing Long Options with getopt_long
  • 25.3 Parsing Program Options with Argp
    • 25.3.1 The argp_parse Function
    • 25.3.2 Argp Global Variables
    • 25.3.3 Specifying Argp Parsers
    • 25.3.4 Specifying Options in an Argp Parser
      • 25.3.4.1 Flags for Argp Options
    • 25.3.5 Argp Parser Functions
      • 25.3.5.1 Special Keys for Argp Parser Functions
      • 25.3.5.2 Functions For Use in Argp Parsers
      • 25.3.5.3 Argp Parsing State
    • 25.3.6 Combining Multiple Argp Parsers
    • 25.3.7 Flags for argp_parse
    • 25.3.8 Customizing Argp Help Output
      • 25.3.8.1 Special Keys for Argp Help Filter Functions
    • 25.3.9 The argp_help Function
    • 25.3.10 Flags for the argp_help Function
    • 25.3.11 Argp Examples
      • 25.3.11.1 A Minimal Program Using Argp
      • 25.3.11.2 A Program Using Argp with Only Default Options
      • 25.3.11.3 A Program Using Argp with User Options
      • 25.3.11.4 A Program Using Multiple Combined Argp Parsers
    • 25.3.12 Argp User Customization
      • 25.3.12.1 Parsing of Suboptions
    • 25.3.13 Parsing of Suboptions Example
  • 25.4 Environment Variables
    • 25.4.1 Environment Access
    • 25.4.2 Standard Environment Variables
  • 25.5 System Calls
  • 25.6 Program Termination
    • 25.6.1 Normal Termination
    • 25.6.2 Exit Status
    • 25.6.3 Cleanups on Exit
    • 25.6.4 Aborting a Program
    • 25.6.5 Termination Internals
• 26 Processes
  • 26.1 Running a Command
  • 26.2 Process Creation Concepts
  • 26.3 Process Identification
  • 26.4 Creating a Process
  • 26.5 Executing a File
  • 26.6 Process Completion
  • 26.7 Process Completion Status
  • 26.8 BSD Process Wait Functions
  • 26.9 Process Creation Example
• 27 Job Control
  • 27.1 Concepts of Job Control
  • 27.2 Job Control is Optional
  • 27.3 Controlling Terminal of a Process
  • 27.4 Access to the Controlling Terminal
  • 27.5 Orphaned Process Groups
  • 27.6 Implementing a Job Control Shell
    • 27.6.1 Data Structures for the Shell
    • 27.6.2 Initializing the Shell
    • 27.6.3 Launching Jobs
    • 27.6.4 Foreground and Background
    • 27.6.5 Stopped and Terminated Jobs
    • 27.6.6 Continuing Stopped Jobs
    • 27.6.7 The Missing Pieces
  • 27.7 Functions for Job Control
    • 27.7.1 Identifying the Controlling Terminal
    • 27.7.2 Process Group Functions
    • 27.7.3 Functions for Controlling Terminal Access
• 28 System Databases and Name Service Switch
  • 28.1 NSS Basics
  • 28.2 The NSS Configuration File
    • 28.2.1 Services in the NSS configuration File
    • 28.2.2 Actions in the NSS configuration
    • 28.2.3 Notes on the NSS Configuration File
  • 28.3 NSS Module Internals
    • 28.3.1 The Naming Scheme of the NSS Modules
    • 28.3.2 The Interface of the Function in NSS Modules
  • 28.4 Extending NSS
    • 28.4.1 Adding another Service to NSS
    • 28.4.2 Internals of the NSS Module Functions
• 29 Users and Groups
  • 29.1 User and Group IDs
  • 29.2 The Persona of a Process
  • 29.3 Why Change the Persona of a Process?
  • 29.4 How an Application Can Change Persona
  • 29.5 Reading the Persona of a Process
  • 29.6 Setting the User ID
  • 29.7 Setting the Group IDs
  • 29.8 Enabling and Disabling Setuid Access
  • 29.9 Setuid Program Example
  • 29.10 Tips for Writing Setuid Programs
  • 29.11 Identifying Who Logged In
  • 29.12 The User Accounting Database
    • 29.12.1 Manipulating the User Accounting Database
    • 29.12.2 XPG User Accounting Database Functions
    • 29.12.3 Logging In and Out
  • 29.13 User Database
    • 29.13.1 The Data Structure that Describes a User
    • 29.13.2 Looking Up One User
    • 29.13.3 Scanning the List of All Users
    • 29.13.4 Writing a User Entry
  • 29.14 Group Database
    • 29.14.1 The Data Structure for a Group
    • 29.14.2 Looking Up One Group
    • 29.14.3 Scanning the List of All Groups
  • 29.15 User and Group Database Example
  • 29.16 Netgroup Database
    • 29.16.1 Netgroup Data
    • 29.16.2 Looking up one Netgroup
    • 29.16.3 Testing for Netgroup Membership
• 30 System Management
  • 30.1 Host Identification
  • 30.2 Platform Type Identification
  • 30.3 Controlling and Querying Mounts
    • 30.3.1 Mount Information
      • 30.3.1.1 The fstab file
      • 30.3.1.2 The mtab file
      • 30.3.1.3 Other (Non-libc) Sources of Mount Information
    • 30.3.2 Mount, Unmount, Remount
  • 30.4 System Parameters
• 31 System Configuration Parameters
  • 31.1 General Capacity Limits
  • 31.2 Overall System Options
  • 31.3 Which Version of POSIX is Supported
  • 31.4 Using sysconf
    • 31.4.1 Definition of sysconf
    • 31.4.2 Constants for sysconf Parameters
    • 31.4.3 Examples of sysconf
  • 31.5 Minimum Values for General Capacity Limits
  • 31.6 Limits on File System Capacity
  • 31.7 Optional Features in File Support
  • 31.8 Minimum Values for File System Limits
  • 31.9 Using pathconf
  • 31.10 Utility Program Capacity Limits
  • 31.11 Minimum Values for Utility Limits
  • 31.12 String-Valued Parameters
• 32 DES Encryption and Password Handling
  • 32.1 Legal Problems
  • 32.2 Reading Passwords
  • 32.3 Encrypting Passwords
  • 32.4 DES Encryption
• 33 Debugging support
  • 33.1 Backtraces
• Appendix A C Language Facilities in the Library
  • A.1 Explicitly Checking Internal Consistency
  • A.2 Variadic Functions
    • A.2.1 Why Variadic Functions are Used
    • A.2.2 How Variadic Functions are Defined and Used
      • A.2.2.1 Syntax for Variable Arguments
      • A.2.2.2 Receiving the Argument Values
      • A.2.2.3 How Many Arguments Were Supplied
      • A.2.2.4 Calling Variadic Functions
      • A.2.2.5 Argument Access Macros
    • A.2.3 Example of a Variadic Function
      • A.2.3.1 Old-Style Variadic Functions
  • A.3 Null Pointer Constant
  • A.4 Important Data Types
  • A.5 Data Type Measurements
    • A.5.1 Computing the Width of an Integer Data Type
    • A.5.2 Range of an Integer Type
    • A.5.3 Floating Type Macros
      • A.5.3.1 Floating Point Representation Concepts
      • A.5.3.2 Floating Point Parameters
      • A.5.3.3 IEEE Floating Point
    • A.5.4 Structure Field Offset Measurement
• Appendix B Summary of Library Facilities
• Appendix C Installing the GNU C Library
  • C.1 Configuring and compiling GNU Libc
  • C.2 Installing the C Library
  • C.3 Recommended Tools for Compilation
  • C.4 Supported Configurations
  • C.5 Specific advice for Linux systems
  • C.6 Reporting Bugs
• Appendix D Library Maintenance
  • D.1 Adding New Functions
  • D.2 Porting the GNU C Library
    • D.2.1 Layout of the sysdeps Directory Hierarchy
    • D.2.2 Porting the GNU C Library to Unix Systems
• Appendix E Contributors to the GNU C Library
• Appendix F Free Software Needs Free Documentation
• Appendix G GNU Lesser General Public License
  • G.0.1 Preamble
  • G.0.2 How to Apply These Terms to Your New Libraries
• Appendix H GNU Free Documentation License
  • H.0.1 ADDENDUM: How to use this License for your documents
• Concept Index
• Type Index
• Function and Macro Index
• Variable and Constant Macro Index
• Program and File Index