The POSIX (IEEE) Standards and the X/Open Specifications are described on the standards page.
Environments
The user environment (environ), the subset of the user environment that depends on language and cultural conventions (locale), the large file compilation environment (lfcompile), and the transitional
compilation environment (lfcompile64) are described.
Macros
The macros to format Reference Manual pages (man and mansun) as well as other text format macros (me, mm, and ms) are described.
Characters
Tables of character sets (ascii, charmap, eqnchar, and iconv), file format notation (formats), file name pattern matching (fnmatch), and
regular expressions (regex and regexp) are presented.