IEEE Standards Interpretations for IEEE Std 1003.2™-1992 IEEE Standard for Information Technology--Portable Operating System Interfaces (POSIX®)--Part 2: Shell and Utilities
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Interpretation Request #80
Topic: awk Relevant Clauses: 4.1
Question 1: Awk POSIX.2, p.167, 220.127.116.11 last paragraph In IEEE 1003.2-1992 Subclause 18.104.22.168, the execution of an awk program is described: "(...) Then each file operand (...) will be processed in turn (...) until a record separator is seen (...), splitting the current record into fields using the current value of FS according to the rules in (...), evaluating each pattern in the program in the order of occurrence, and executing the action associated with each pattern that matches the current record. (...)". Existing practice has always been to implement splitting into fields in a lazy fashion. If only $0 was needed, no splitting occurs. If awk must be changed, the obvious modification will cause a noticeable slow-down since all lines will split regardless of whether they will be processed. Was the change from existing practice intentional?
Question 2: Awk POSIX.2, p.164, 4.1.4 POSIX.2 Subclause 4.1.4 states: "Thus, an assignment before the first file argument shall be executed after the BEGIN actions (if any),..." Existing practice has been to make the command line variable assignments all at once before the BEGIN. Was this change intentional?
Question 1: The standard clearly states the effects expected from awk and a conforming implementation must just support the effects expected from awk. It does not define the implementation and an implementation could still continue to split fields in a lazy fashion.
Question 2: The standard states the behavior for the assignment argument for awk, and conforming implementations must conform to this. However, concerns have been raised about this which are being referred to the sponsor.
Rationale for Interpretation