POSIX (The GNU Awk User’s Guide)
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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)
- The use of predefined variables as function parameter names is forbidden (see section Function 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 section Input/Output Functions) - The
nextfile
statement (see section The nextfile Statement) - The ability to delete all of an array at once with ‘
delete array
’ (see section The delete Statement)
See section Common Extensions Summary for a list of common extensions not permitted by the POSIX standard.
The 2018 POSIX standard can be found online at https://pubs.opengroup.org/onlinepubs/9699919799/.