The newest standard for Programming Language C is C17/C18 ISO/IEC 9899:2018 published 2018-06, available for purchase from ISO. C17 addresses defects in C11 without introducing new language features. C11 added atomic objects, threads, and unicode to the language. C99 included many major changes to the original C89/90 standard. The rationale for the C99 standard is also available.
The Most Expensive One-Byte Mistake, Poul-Henning Kamp, CACM, Sept. 2011.
See the volume on Shell & Utilities, Chapter 2 Shell Command Language and Chapter 4 Utilities.
Shell: Detailed Table of Contents
sh - man page
For example, support for threads is only available in libc-2.28 as of August 2018, but current Linux distributions generally have an earlier version. However, a C11 threads.h implementation using POSIX threads is available from github.com/jtsiomb/c11threads.
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