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Extensions in the Bell Laboratories awk

Brian Kernighan, one of the original designers of Unix awk, has made his version available via his home page (see Other Freely Available awk Implementations). This section describes extensions in his version of awk that are not in POSIX awk:

• The -mf N and -mr N command-line options to set the maximum number of fields and the maximum record size, respectively (see Command-Line Options). As a side note, his awk no longer needs these options; it continues to accept them to avoid breaking old programs.
• The fflush built-in function for flushing buffered output (see Input/Output Functions).
• The ** and **= operators (see Arithmetic Operators and Assignment Expressions).
• The use of func as an abbreviation for function (see Function Definition Syntax).

The Bell Laboratories awk also incorporates the following extensions, originally developed for gawk:

• The \x escape sequence (see Escape Sequences).
• The /dev/stdin, /dev/stdout, and /dev/stderr special files (see Special File Names in gawk).
• The ability for FS and for the third argument to split to be null strings (see Making Each Character a Separate Field).
• The nextfile statement (see Using gawk's nextfile Statement).
• The ability to delete all of an array at once with delete array (see The delete Statement).