The GNU C Library


Reference Manual



Sandra Loosemore

with

Roland McGrath, Andrew Oram, and Richard M. Stallman




Edition 0.05


last updated 30 August 1993


for version 1.07 Beta

Copyright © 1993 Free Software Foundation, Inc.



Published by the Free Software Foundation
675 Massachusetts Avenue,
Cambridge, MA 02139 USA
Printed copies are available for $50 each.

Permission is granted to make and distribute verbatim copies of this manual provided the copyright notice and this permission notice are preserved on all copies.

Permission is granted to copy and distribute modified versions of this manual under the conditions for verbatim copying, provided also that the section entitled “GNU Library General Public License” is included exactly as in the original, and provided that the entire resulting derived work is distributed under the terms of a permission notice identical to this one.

Permission is granted to copy and distribute translations of this manual into another language, under the above conditions for modified versions, except that the text of the translation of the section entitled “GNU Library General Public License” must be approved for accuracy by the Foundation.

• Introduction   Purpose of the GNU C Library.
• Error Reporting   How the GNU Library functions report error conditions.
• Memory Allocation   Your program can allocate memory dynamically and manipulate it via pointers.
• Character Handling   Character testing and conversion functions.
• String and Array Utilities   Utilities for copying and comparing strings and arrays.
• Extended Characters   Support for extended character sets.
• Locales   The country and language can affect the behavior of library functions.
• Searching and Sorting   General searching and sorting functions.
• Pattern Matching   Matching wildcards and regular expressions, and shell-style “word expansion”.
• I/O Overview   Introduction to the I/O facilities.
• Streams   High-level, portable I/O facilities.
• Low-Level I/O   Low-level, less portable I/O.
• File System Interface   Functions for manipulating files.
• Pipes and FIFOs   A simple interprocess communication mechanism.
• Sockets   A more complicated interprocess communication mechanism, with support for networking.
• Low-Level Terminal Interface  How to change the characteristics of a terminal device.
• Mathematics   Math functions (transcendental functions, random numbers, absolute value, etc.).
• Arithmetic   Low-level arithmetic functions.
• Date and Time   Functions for getting the date and time, and for conversion between formats.
• Non-Local Exits   The setjmp and longjmp facilities.
• Signal Handling   All about signals; how to send them, block them, and handle them.
• Process Startup   Writing the beginning and end of your program.
• Child Processes   How to create processes and run other programs.
• Job Control   All about process groups and sessions.
• Users and Groups   How users are identified and classified.
• System Information   Getting information about the hardware and software configuration of the machine a program runs on.
• System Configuration   Parameters describing operating system limits. 
Appendices
• Language Features   C language features provided by the library.
• Library Summary   A summary showing the syntax, header file, and derivation of each library feature.
• Maintenance   How to install and maintain the GNU C Library.
• Copying   The GNU Library General Public License says how you can copy and share the GNU C Library. 
Indices
Concept Index   Index of concepts and names.
Type Index   Index of types and type qualifiers.
Function and Macro Index   Index of functions and function-like macros.
Variable and Constant Macro Index   Index of variables and variable-like macros.
Program and File Index   Index of programs and files. 
 — The Detailed Node Listing —

Introduction
• Getting Started  
• Standards and Portability  
• Using the Library  
• Roadmap to the Manual  
Standards and Portability
• ANSI C   The American National Standard for the C programming language.
• POSIX   The IEEE 1003 standards for operating systems.
• Berkeley Unix   BSD and SunOS.
• SVID   The System V Interface Description. 
Using the Library
• Header Files   How to use the header files in your programs.
• Macro Definitions   Some functions in the library may really be implemented as macros.
• Reserved Names   The C standard reserves some names for the library, and some for users.
• Feature Test Macros   How to control what names are defined. 
Error Reporting
• Checking for Errors   How errors are reported by library functions.
• Error Codes   What all the error codes are.
• Error Messages   Mapping error codes onto error messages. 
Memory Allocation
• Memory Concepts   An introduction to concepts and terminology.
• Dynamic Allocation and C   How to get different kinds of allocation in C.
• Unconstrained Allocation   The malloc facility allows fully general dynamic allocation.
• Obstacks   Obstacks are less general than malloc but more efficient and convenient.
• Variable Size Automatic   Allocation of variable-sized blocks of automatic storage that are freed when the calling function returns.
• Relocating Allocator   Waste less memory, if you can tolerate automatic relocation of the blocks you get.
• Memory Warnings   Getting warnings when memory is nearly full. 
Unconstrained Allocation
• Basic Allocation   Simple use of malloc.
• Malloc Examples   Examples of malloc. xmalloc.
• Freeing after Malloc   Use free to free a block you got with malloc.
• Changing Block Size   Use realloc to make a block bigger or smaller.
• Allocating Cleared Space   Use calloc to allocate a block and clear it.
• Efficiency and Malloc   Efficiency considerations in use of these functions.
• Aligned Memory Blocks   Allocating specially aligned memory: memalign and valloc.
• Heap Consistency Checking   Automatic checking for errors.
• Hooks for Malloc   You can use these hooks for debugging programs that use malloc.
• Statistics of Malloc   Getting information about how much memory your program is using.
• Summary of Malloc   Summary of malloc and related functions. 
Obstacks
• Creating Obstacks   How to declare an obstack in your program.
• Preparing for Obstacks   Preparations needed before you can use obstacks.
• Allocation in an Obstack   Allocating objects in an obstack.
• Freeing Obstack Objects   Freeing objects in an obstack.
• Obstack Functions   The obstack functions are both functions and macros.
• Growing Objects   Making an object bigger by stages.
• Extra Fast Growing   Extra-high-efficiency (though more complicated) growing objects.
• Status of an Obstack   Inquiries about the status of an obstack.
• Obstacks Data Alignment   Controlling alignment of objects in obstacks.
• Obstack Chunks   How obstacks obtain and release chunks. Efficiency considerations.
• Summary of Obstacks   
Automatic Storage with Variable Size
• Alloca Example   Example of using alloca.
• Advantages of Alloca   Reasons to use alloca.
• Disadvantages of Alloca   Reasons to avoid alloca.
• GNU C Variable-Size Arrays   Only in GNU C, here is an alternative method of allocating dynamically and freeing automatically. Relocating Allocator
• Relocator Concepts   How to understand relocating allocation.
• Using Relocator   Functions for relocating allocation. 
Character Handling
• Classification of Characters  Testing whether characters are letters, digits, punctuation, etc.
• Case Conversion   Case mapping, and the like. 
String and Array Utilities
• Representation of Strings   Introduction to basic concepts.
• String/Array Conventions   Whether to use a string function or an arbitrary array function.
• String Length   Determining the length of a string.
• Copying and Concatenation   Functions to copy the contents of strings and arrays.
• String/Array Comparison   Functions for byte-wise and character-wise comparison.
• Collation Functions   Functions for collating strings.
• Search Functions   Searching for a specific element or substring.
• Finding Tokens in a String   Splitting a string into tokens by looking for delimiters. 
Extended Characters
• Extended Char Intro   Multibyte codes versus wide characters.
• Locales and Extended Chars   The locale selects the character codes.
• Multibyte Char Intro   How multibyte codes are represented.
• Wide Char Intro   How wide characters are represented.
• Wide String Conversion   Converting wide strings to multibyte code and vice versa.
• Length of Char   how many bytes make up one multibyte char.
• Converting One Char   Converting a string character by character.
• Example of Conversion   Example showing why converting one character at a time may be useful.
• Shift State   Multibyte codes with "shift characters". 
Locales and Internationalization
• Effects of Locale   Actions affected by the choice of locale.
• Choosing Locale   How the user specifies a locale.
• Locale Categories   Different purposes for which you can select a locale.
• Setting the Locale   How a program specifies the locale.
• Standard Locales   Locale names available on all systems.
• Numeric Formatting   How to format numbers for the chosen locale. 
Searching and Sorting
• Comparison Functions   Defining how to compare two objects. Since the sort and search facilities are general, you have to specify the ordering.
• Array Search Function   The bsearch function.
• Array Sort Function   The qsort function.
• Search/Sort Example   An example program. 
Pattern Matching
• Wildcard Matching   Matching a wildcard pattern against a single string.
• Globbing   Finding the files that match a wildcard pattern.
• Regular Expressions   Matching regular expressions against strings.
• Word Expansion   Expanding shell variables, nested commands, arithmetic, and wildcards. This is what the shell does with shell commands. 
I/O Overview
• I/O Concepts   Some basic information and terminology.
• File Names   How to refer to a file. 
I/O Concepts
• Streams and File Descriptors   The GNU Library provides two ways to access the contents of files.
• File Position   The number of bytes from the beginning of the file. 
File Names
• Directories   Directories contain entries for files.
• File Name Resolution   A file name specifies how to look up a file.
• File Name Errors   Error conditions relating to file names.
• File Name Portability   File name portability and syntax issues. 
I/O on Streams
• Streams   About the data type representing a stream.
• Standard Streams   Streams to the standard input and output devices are created for you.
• Opening Streams   How to create a stream to talk to a file.
• Closing Streams   Close a stream when you are finished with it.
• Simple Output   Unformatted output by characters and lines.
• Character Input   Unformatted input by characters and words.
• Line Input   Reading a line or a record from a stream.
• Unreading   Peeking ahead/pushing back input just read.
• Formatted Output   printf and related functions.
• Customizing Printf   You can define new conversion specifiers for printf and friends.
• Formatted Input   scanf and related functions.
• Block Input/Output   Input and output operations on blocks of data.
• EOF and Errors   How you can tell if an I/O error happens.
• Binary Streams   Some systems distinguish between text files and binary files.
• File Positioning   About random-access streams.
• Portable Positioning   Random access on peculiar ANSI C systems.
• Stream Buffering   How to control buffering of streams.
• Temporary Files   How to open a temporary file.
• Other Kinds of Streams  
Unreading
• Unreading Idea   An explanation of unreading with pictures.
• How Unread   How to call ungetc to do unreading. 
Formatted Output
• Formatted Output Basics   Some examples to get you started.
• Output Conversion Syntax   General syntax of conversion specifications.
• Table of Output Conversions   Summary of output conversions, what they do.
• Integer Conversions   Details of formatting integers.
• Floating-Point Conversions   Details of formatting floating-point numbers.
• Other Output Conversions   Details about formatting of strings, characters, pointers, and the like.
• Formatted Output Functions   Descriptions of the actual functions.
• Variable Arguments Output   vprintf and friends.
• Parsing a Template String   What kinds of arguments does a given template call for? 
Customizing Printf
• Registering New Conversions  
• Conversion Specifier Options  
• Defining the Output Handler  
• Printf Extension Example   
Formatted Input
• Formatted Input Basics   Some basics to get you started.
• Input Conversion Syntax   Syntax of conversion specifications.
• Table of Input Conversions   Summary of input conversions and what they do.
• Numeric Input Conversions   Details of conversions for reading numbers.
• String Input Conversions   Details of conversions for reading strings.
• Other Input Conversions   Details of miscellaneous other conversions.
• Formatted Input Functions   Descriptions of the actual functions.
• Variable Arguments Input   vscanf and friends. 
Stream Buffering
• Buffering Concepts   Terminology is defined here.
• Flushing Buffers   How to ensure that output buffers are flushed.
• Controlling Buffering   How to specify what kind of buffering to use. 
Other Kinds of Streams
• String Streams  
• Custom Streams   
Programming Your Own Custom Streams
• Streams and Cookies  
• Hook Functions   
Low-Level I/O
• Opening and Closing Files   How to open and close file descriptors.
• I/O Primitives   Reading and writing data.
• File Position Primitive   Setting a descriptor’s file position.
• Descriptors and Streams   Converting descriptor to stream or vice-versa.
• Stream/Descriptor Precautions   Precautions needed if you use both descriptors and streams.
• Waiting for I/O   How to check for input or output on multiple file descriptors.
• Control Operations   Various other operations on file descriptors.
• Duplicating Descriptors   Fcntl commands for duplicating descriptors.
• Descriptor Flags   Fcntl commands for manipulating flags associated with file descriptors.
• File Status Flags   Fcntl commands for manipulating flags associated with open files.
• File Locks   Fcntl commands for implementing file locking.
• Interrupt Input   Getting a signal when input arrives. 
File System Interface
• Working Directory   This is used to resolve relative file names.
• Accessing Directories   Finding out what files a directory contains.
• Hard Links   Adding alternate names to a file.
• Symbolic Links   A file that “points to” a file name.
• Deleting Files   How to delete a file, and what that means.
• Renaming Files   Changing a file’s name.
• Creating Directories   A system call just for creating a directory.
• File Attributes   Attributes of individual files.
• Making Special Files   How to create special files. 
Accessing Directories
• Directory Entries   Format of one directory entry.
• Opening a Directory   How to open a directory stream.
• Reading/Closing Directory   How to read directory entries from the stream.
• Simple Directory Lister   A very simple directory listing program.
• Random Access Directory   Rereading part of the directory already read with the same stream. 
File Attributes
• Attribute Meanings   The names of the file attributes, and what their values mean.
• Reading Attributes   How to read the attributes of a file.
• Testing File Type   Distinguishing ordinary files, directories, links...
• File Owner   How ownership for new files is determined, and how to change it.
• Permission Bits   How information about a file’s access mode is stored.
• Access Permission   How the system decides who can access a file.
• Setting Permissions   How permissions for new files are assigned, and how to change them.
• Testing File Access   How to find out if your process can access a file.
• File Times   About the time attributes of a file. 
Pipes and FIFOs
• Creating a Pipe   Making a pipe with the pipe function.
• Pipe to a Subprocess   Using a pipe to communicate with a child.
• FIFO Special Files   Making a FIFO special file. 
Sockets
• Socket Concepts   Basic concepts you need to know about.
• Communication Styles   Stream communication, datagrams, and others.
• Socket Addresses   How socket names (“addresses”) work.
• File Namespace   Details about the file namespace.
• Internet Namespace   Details about the Internet namespace.
• Open/Close Sockets   Creating sockets and destroying them.
• Connections   Operations on sockets with connection state.
• Datagrams   Operations on datagram sockets.
• Socket Options   Miscellaneous low-level socket options.
• Networks Database   Accessing the database of network names. 
Socket Addresses
• Address Formats   About struct sockaddr.
• Setting Address   Binding an address to a socket.
• Reading Address   Reading the address of a socket. 
Internet Domain
• Internet Address Format   How socket addresses are specified in the Internet namespace.
• Host Addresses   All about host addresses of Internet hosts.
• Protocols Database   Referring to protocols by name.
• Services Database   Ports may have symbolic names.
• Byte Order   Different hosts may use different byte ordering conventions; you need to canonicalize host address and port number.
• Inet Example   Putting it all together. 
Host Addresses
• Abstract Host Addresses   What a host number consists of.
• Data type   Data type for a host number.
• Functions   Functions to operate on them.
• Names   Translating host names to host numbers. 
Open/Close Sockets
• Creating a Socket   How to open a socket.
• Closing a Socket   How to close a socket.
• Socket Pairs   These are created like pipes. 
Connections
• Connecting   What the client program must do.
• Listening   How a server program waits for requests.
• Accepting Connections   What the server does when it gets a request.
• Who is Connected   Getting the address of the other side of a connection.
• Transferring Data   How to send and receive data.
• Byte Stream Example   An example client for communicating over a byte stream socket in the Internet namespace.
• Server Example   A corresponding server program.
• Out-of-Band Data   This is an advanced feature. 
Transferring Data
• Sending Data   Sending data with write.
• Receiving Data   Reading data with read.
• Socket Data Options   Using send and recv. 
Datagrams
• Sending Datagrams   Sending packets on a datagram socket.
• Receiving Datagrams   Receiving packets on a datagram socket.
• Datagram Example   An example program: packets sent over a datagram stream in the file namespace.
• Example Receiver   Another program, that receives those packets. 
Socket Options
• Socket Option Functions   The basic functions for setting and getting socket options.
• Socket-Level Options   Details of the options at the socket level. 
Low-Level Terminal Interface
• Is It a Terminal   How to determine if a file is a terminal device, and what its name is.
• I/O Queues   About flow control and typeahead.
• Canonical or Not   Two basic styles of input processing.
• Terminal Modes   How to examine and modify flags controlling terminal I/O: echoing, signals, editing.
• Line Control   Sending break sequences, clearing buffers...
• Noncanon Example   How to read single characters without echo. 
Terminal Modes
• Mode Data Types   The data type struct termios and related types.
• Mode Functions   Functions to read and set terminal attributes.
• Setting Modes   The right way to set attributes reliably.
• Input Modes   Flags controlling low-level input handling.
• Output Modes   Flags controlling low-level output handling.
• Control Modes   Flags controlling serial port behavior.
• Local Modes   Flags controlling high-level input handling.
• Line Speed   How to read and set the terminal line speed.
• Special Characters   Characters that have special effects, and how to change them.
• Noncanonical Input   Controlling how long to wait for input. 
Special Characters
• Editing Characters  
• Signal Characters  
• Start/Stop Characters   
Mathematics
• Domain and Range Errors   How overflow conditions and the like are reported.
• Not a Number   Making NANs and testing for NANs.
• Trig Functions   Sine, cosine, and tangent.
• Inverse Trig Functions   Arc sine, arc cosine, and arc tangent.
• Exponents and Logarithms   Also includes square root.
• Hyperbolic Functions   Hyperbolic sine and friends.
• Pseudo-Random Numbers   Functions for generating pseudo-random numbers.
• Absolute Value   Absolute value functions. 
Pseudo-Random Numbers
• ANSI Random   rand and friends.
• BSD Random   random and friends. 
Low-Level Arithmetic Functions
• Normalization Functions   Hacks for radix-2 representations.
• Rounding and Remainders   Determinining the integer and fractional parts of a float.
• Integer Division   Functions for performing integer division.
• Parsing of Numbers   Functions for “reading” numbers from strings.
• Predicates on Floats   Some miscellaneous test functions. 
Parsing of Numbers
• Parsing of Integers   Functions for conversion of integer values.
• Parsing of Floats   Functions for conversion of floating-point. 
Date and Time
• Processor Time   Measures processor time used by a program.
• Calendar Time   Manipulation of “real” dates and times.
• Setting an Alarm   Sending a signal after a specified time.
• Sleeping   Waiting for a period of time. 
Processor Time
• Basic CPU Time   The clock function.
• Detailed CPU Time   The times function. 
Calendar Time
• Simple Calendar Time   Facilities for manipulating calendar time.
• High-Resolution Calendar   A time representation with greater precision.
• Broken-down Time   Facilities for manipulating local time.
• Formatting Date and Time   Converting times to strings.
• TZ Variable   How users specify the time zone.
• Time Zone Functions   Functions to examine or specify the time zone.
• Time Functions Example   An example program showing use of some of the time functions. 
Signal Handling
• Concepts of Signals   Introduction to the signal facilities.
• Standard Signals   Particular kinds of signals with standard names and meanings.
• Signal Actions   Specifying what happens when a particular signal is delivered.
• Defining Handlers   How to write a signal handler function.
• Generating Signals   How to send a signal to a process.
• Blocking Signals   Making the system hold signals temporarily.
• Waiting for a Signal   Suspending your program until a signal arrives.
• BSD Signal Handling   Additional functions for backward compatibility with BSD.
• BSD Handler   BSD Function to Establish a Handler 
Basic Concepts of Signals
• Kinds of Signals   Some examples of what can cause a signal.
• Signal Generation   Concepts of why and how signals occur.
• Delivery of Signal   Concepts of what a signal does to the process. 
Standard Signals
• Program Error Signals   Used to report serious program errors.
• Termination Signals   Used to interrupt and/or terminate the program.
• Alarm Signals   Used to indicate expiration of timers.
• Asynchronous I/O Signals   Used to indicate input is available.
• Job Control Signals   Signals used to support job control.
• Miscellaneous Signals  
• Nonstandard Signals   Implementations can support other signals.
• Signal Messages   Printing a message describing a signal. 
Specifying Signal Actions
• Basic Signal Handling   The simple signal function.
• Advanced Signal Handling   The more powerful sigaction function.
• Signal and Sigaction   How those two functions interact.
• Sigaction Function Example   An example of using the sigaction function.
• Flags for Sigaction   Specifying options for signal handling.
• Initial Signal Actions   How programs inherit signal actions. 
Defining Signal Handlers
• Handler Returns  
• Termination in Handler  
• Longjmp in Handler  
• Signals in Handler  
• Nonreentrancy  
• Atomic Data Access   
Generating Signals
• Signaling Yourself  
• Signaling Another Process   Send a signal to another process.
• Permission for kill   Permission for using kill
• Kill Example   Using kill for Communication 
Blocking Signals
• Why Block   The purpose of blocking signals.
• Signal Sets   How to specify which signals to block.
• Process Signal Mask   Blocking delivery of signals to your process during normal execution.
• Testing for Delivery   Blocking to Test for Delivery of a Signal
• Blocking for Handler   Blocking additional signals while a handler is being run.
• Checking for Pending Signals  
• Remembering a Signal   How you can get almost the same effect as blocking a signal, by handling it and setting a flag to be tested later. 
Waiting for a Signal
• Using Pause   The simple way, using pause.
• Pause Problems   Why the simple way is often not very good.
• Sigsuspend   Reliably waiting for a specific signal. 
BSD Signal Handling
• POSIX vs BSD   Comparison of BSD and POSIX signal functions. 
BSD Function to Establish a Handler
• Blocking in BSD   BSD Functions for Blocking Signals
• Signal Stack   Using a Separate Signal Stack 
Process Startup and Termination
• Program Arguments   Parsing your program’s command-line arguments.
• Environment Variables   How to access parameters inherited from a parent process.
• Program Termination   How to cause a process to terminate and return status information to its parent. 
Program Arguments
• Argument Syntax   By convention, options start with a hyphen.
• Parsing Options   The getopt function.
• Example of Getopt   An example of parsing options with getopt.
• Long Options   GNU utilities should accept long-named options. Here is how to do that.
• Long Option Example   An example of using getopt_long. 
Environment Variables
• Environment Access   How to get and set the values of environment variables.
• Standard Environment   These environment variables have standard interpretations. 
Program Termination
• Normal Termination   If a program calls exit, a process terminates normally.
• Exit Status   The exit status provides information about why the process terminated.
• Cleanups on Exit   A process can run its own cleanup functions upon normal termination.
• Aborting a Program   The abort function causes abnormal program termination.
• Termination Internals   What happens when a process terminates. 
Child Processes
• Running a Command   The easy way to run another program.
• Process Creation Concepts   An overview of the hard way to do it.
• Process Identification   How to get the process ID of a process.
• Creating a Process   How to fork a child process.
• Executing a File   How to make a child execute another program.
• Process Completion   How to tell when a child process has completed.
• Process Completion Status   How to interpret the status value returned from a child process.
• BSD Wait Functions   More functions, for backward compatibility.
• Process Creation Example   A complete example program. 
Job Control
• Concepts of Job Control   
• Job Control is Optional   Not all POSIX systems support job control.
• Controlling Terminal   How a process gets its controlling terminal.
• Access to the Terminal   How processes share the controlling terminal.
• Orphaned Process Groups   Jobs left after the user logs out.
• Implementing a Shell   What a shell must do to implement job control.
• Functions for Job Control   Functions to control process groups. 
Implementing a Job Control Shell
• Data Structures   Introduction to the sample shell.
• Initializing the Shell   What the shell must do to take responsibility for job control.
• Launching Jobs   Creating jobs to execute commands.
• Foreground and Background   Putting a job in foreground of background.
• Stopped and Terminated Jobs   Reporting job status.
• Continuing Stopped Jobs   How to continue a stopped job in the foreground or background.
• Missing Pieces   Other parts of the shell. 
Functions for Job Control
• Identifying the Terminal   Determining the controlling terminal’s name.
• Process Group Functions   Functions for manipulating process groups.
• Terminal Access Functions   Functions for controlling terminal access. 
Users and Groups
• User and Group IDs   Each user and group has a unique numeric ID.
• Process Persona   The user IDs and group IDs of a process.
• Why Change Persona   Why a program might need to change its user and/or group IDs.
• How Change Persona   Restrictions on changing user and group IDs.
• Reading Persona   Examining the process’s user and group IDs.
• Setting User ID  
• Setting Groups  
• Enable/Disable Setuid  
• Setuid Program Example  
• Tips for Setuid  
• Who Logged In   Getting the name of the user who logged in, or of the real user ID of the current process.
• User Database   Functions and data structures for accessing the user database.
• Group Database   Functions and data structures for accessing the group database.
• Database Example   Example program showing use of database inquiry functions. 
User Database
• User Data Structure  
• Lookup User  
• Scanning All Users   Scanning the List of All Users
• Writing a User Entry   
Group Database
• Group Data Structure  
• Lookup Group  
• Scanning All Groups   Scanning the List of All Groups 
System Information
• Host Identification   Determining the name of the machine.
• Hardware/Software Type ID   Determining the hardware type and operating system type. 
System Configuration Limits
• General Limits   Constants and functions that describe various process-related limits that have one uniform value for any given machine.
• System Options   Optional POSIX features.
• Version Supported   Version numbers of POSIX.1 and POSIX.2.
• Sysconf   Getting specific configuration values of general limits and system options.
• Minimums   Minimum values for general limits.
• Limits for Files   Size limitations on individual files. These can vary between file systems or even from file to file.
• Options for Files   Optional features that some files may support.
• File Minimums   Minimum values for file limits.
• Pathconf   Getting the limit values for a particular file.
• Utility Limits   Capacity limits of POSIX.2 utility programs.
• Utility Minimums   Minimum allowable values of those limits.
• String Parameters   Getting the default search path. 
Library Facilities that are Part of the C Language
• Consistency Checking   Using assert to abort if something “impossible” happens.
• Variadic Functions   Defining functions with varying numbers of arguments.
• Null Pointer Constant   The macro NULL.
• Important Data Types   Data types for object sizes.
• Data Type Measurements   Parameters of data type representations. 
Variadic Functions
• Why Variadic   Reasons for making functions take variable arguments.
• How Variadic   How to define and call variadic functions.
• Argument Macros   Detailed specification of the macros for accessing variable arguments.
• Variadic Example   A complete example. 
How Variadic Functions are Defined and Used
• Variadic Prototypes   How to make a prototype for a function with variable arguments.
• Receiving Arguments   Steps you must follow to access the optional argument values.
• How Many Arguments   How to decide whether there are more arguments.
• Calling Variadics   Things you need to know about calling variable arguments functions. 
Data Type Measurements
• Width of Type   How many bits does an integer type hold?
• Range of Type   What are the largest and smallest values that an integer type can hold?
• Floating Type Macros   Parameters that measure floating-point types.
• Structure Measurement   Getting measurements on structure types. 
Floating Type Macros
• Floating Point Concepts   Definitions of terminology.
• Floating Point Parameters   Dimensions, limits of floating point types.
• IEEE Floating Point   How one common representation is described. 
Library Maintenance
• Installation   How to configure, compile and install the GNU C library.
• Reporting Bugs   How to report bugs (if you want to get them fixed) and other troubles you may have with the GNU C library.
• Porting   How to port the GNU C library to a new machine or operating system.
• Contributors   Who wrote what parts of the GNU C Library. 
Porting the GNU C Library
• Hierarchy Conventions   How the ‘sysdeps’ hierarchy is layed out.
• Porting to Unix   Porting the library to an average Unix-like system.
[ << ] [ < ] [ Up ] [ > ] [ >> ]         [Top] [Contents] [Index] [ ? ]

Concept Index

[ << ] [ < ] [ Up ] [ > ] [ >> ]         [Top] [Contents] [Index] [ ? ]

Type Index

[ << ] [ < ] [ Up ] [ > ] [ >> ]         [Top] [Contents] [Index] [ ? ]

Function and Macro Index

[ << ] [ < ] [ Up ] [ > ] [ >> ]         [Top] [Contents] [Index] [ ? ]

Variable and Constant Macro Index

[ << ] [ < ] [ Up ] [ > ] [ >> ]         [Top] [Contents] [Index] [ ? ]

Program and File Index

[Top] [Contents] [Index] [ ? ]

Table of Contents

[Top] [Contents] [Index] [ ? ]

Short Table of Contents

[Top] [Contents] [Index] [ ? ]

About This Document

This document was generated on January 16, 2023 using texi2html 5.0.

The buttons in the navigation panels have the following meaning:

Button Name Go to From 1.2.3 go to
[ << ] FastBack Beginning of this chapter or previous chapter 1
[ < ] Back Previous section in reading order 1.2.2
[ Up ] Up Up section 1.2
[ > ] Forward Next section in reading order 1.2.4
[ >> ] FastForward Next chapter 2
[Top] Top Cover (top) of document  
[Contents] Contents Table of contents  
[Index] Index Index  
[ ? ] About About (help)  

where the Example assumes that the current position is at Subsubsection One-Two-Three of a document of the following structure:

This document was generated on January 16, 2023 using texi2html 5.0.