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The GNU Awk User's Guide

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 section Command-Line Options).

• The use of CONVFMT for controlling the conversion of numbers to strings (see section Conversion of Strings and Numbers).

• The concept of a numeric string and tighter comparison rules to go with it (see section Variable Typing and Comparison Expressions).

• 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 section 3.2 Escape Sequences).

• Newlines do not act as whitespace to separate fields when FS is equal to a single space (see section Examining Fields).

• Newlines are not allowed after `?' or `:' (see section Conditional Expressions).

• The synonym func for the keyword function is not recognized (see section Function Definition Syntax).

• The operators `**' and `**=' cannot be used in place of `^' and `^=' (see section Arithmetic Operators, and Assignment Expressions).

• Specifying `-Ft' on the command line does not set the value of FS to be a single TAB character (see section Specifying How Fields Are Separated).

• The fflush built-in function is not supported (see section Input/Output Functions).