C語言 有一套標準庫，standard library, 對高手而言，可能覺得其功能陽春，所以會介紹其他不錯用的函式庫來補其不及。

但是筆者顯然是基礎條件不足，有時，並不覺得標準庫不好用，一定要用第三方庫。

glibc, 和GLIB 是兩個完全不同的庫。

glibc，是GNU C LIBRARY，GNU版的標準庫，當然會有更大的相容性，更多的外掛功能，相對於其他 C語言實作版本的標準庫而言。

https://www.gnu.org/software/libc/manual/html_mono/libc.html#toc-POSIX-Threads-1

它所依據的標準，來自五個方面，

• ISO C: The international standard for the C programming language.

• POSIX: The ISO/IEC 9945 (aka IEEE 1003) standards for operating systems.

• Berkeley Unix: BSD and SunOS.

• SVID: The System V Interface Description.

• XPG: The X/Open Portability Guide.

在泛UNIX-LIKE的OS裏，主要就是這些標準。

而整個glibc 裏面, 包山包海，要含蓋上面的5個標準，

This is The GNU C Library Reference Manual, for Version 2.20 of the GNU C Library.

• Introduction: Purpose of the GNU C Library.

• Error Reporting: How library functions report errors.

• Memory: Allocating virtual memory and controlling paging.

• Character Handling: Character testing and conversion functions.

• String and Array Utilities: Utilities for copying and comparing strings and arrays.

• Character Set Handling: Support for extended character sets.

• Locales: The country and language can affect the behavior of library functions.

• Message Translation: How to make the program speak the user’s language.

• Searching and Sorting: General searching and sorting functions.

• Pattern Matching: Matching shell “globs” and regular expressions.

• I/O Overview: Introduction to the I/O facilities.

• I/O on 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 IPC mechanism, with networking support.

• Low-Level Terminal Interface: How to change the characteristics of a terminal device.

• Syslog: System logging and messaging.

• Mathematics: Math functions, useful constants, random numbers.

• Arithmetic: Low level arithmetic functions.

• Date and Time: Functions for getting the date and time and formatting them nicely.

• Resource Usage And Limitation: Functions for examining resource usage and getting and setting limits.

• Non-Local Exits: Jumping out of nested function calls.

• Signal Handling: How to send, block, and handle signals.

• Program Basics: Writing the beginning and end of your program.

• Processes: How to create processes and run other programs.

• Inter-Process Communication: All about inter-process communication.

• Job Control: All about process groups and sessions.

• Name Service Switch: Accessing system databases.

• Users and Groups: How users are identified and classified.

• System Management: Controlling the system and getting information about it.

• System Configuration: Parameters describing operating system limits.

• Cryptographic Functions: DES encryption and password handling.

• Debugging Support: Functions to help debugging applications.

• POSIX Threads: POSIX Threads.

•Internal Probes: Probes to monitor libc internal behavior.

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.

• Installation: How to install the GNU C Library.

• Maintenance: How to enhance and port the GNU C Library.

• Platform: Describe all platform-specific facilities provided.

• Contributors: Who wrote what parts of the GNU C Library.

• Free Manuals: Free Software Needs Free Documentation.

• Copying: The GNU Lesser General Public License says how you can copy and share the GNU C Library.

• Documentation License: This manual is under the GNU Free Documentation License.

有些人會覺得與其抓很多葉子，不如抓幾根樹幹，顯然glibc也許不是最簡便，但卻是最基礎的。雖然標準化很久了，現在仍以每年一版的速度更新著。