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)
• The use of predefined variables as function parameter names is forbidden (see Definition Syntax)
• More complete documentation of many of the previously undocumented features of the language

In 2012, a number of extensions that had been commonly available for many years were finally added to POSIX. They are:

• The fflush() built-in function for flushing buffered output (see I/O Functions)
• The nextfile statement (see Nextfile Statement)
• The ability to delete all of an array at once with ‘delete array’ (see Delete)

See Common Extensions for a list of common extensions not permitted by the POSIX standard.

The 2008 POSIX standard can be found online at http://www.opengroup.org/onlinepubs/9699919799/.