A.3 Changes Between SVR4 and POSIX awk

The POSIX Command Language and Utilities standard for awk (1992) introduced the following changes into the language:

• The use of -W for implementation-specific options (see Options).
• The use of CONVFMT for controlling the conversion of numbers to strings (see Conversion).
• The concept of a numeric string and tighter comparison rules to go with it (see Typing and Comparison).
• More complete documentation of many of the previously undocumented features of the language.

The following common extensions are not permitted by the POSIX standard:

• \x escape sequences are not recognized (see Escape Sequences).
• Newlines do not act as whitespace to separate fields when FS is equal to a single space (see Fields).
• Newlines are not allowed after `?' or `:' (see Conditional Exp).
• The synonym func for the keyword function is not recognized (see Definition Syntax).
• The operators `**' and `**=' cannot be used in place of `^' and `^=' (see Arithmetic Ops, and Assignment Ops).
• Specifying `-Ft' on the command line does not set the value of FS to be a single TAB character (see Field Separators).
• The fflush built-in function is not supported (see I/O Functions).