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Last update: 1997-05-20
9945-2-81 _____________________________________________________________________________ Topic: sed Relevant Sections: 4.55 Defect Report: ----------------------- Date: Fri, 7 Oct 1994 15:26:29 -0700 From: Fred Zlotnick <[email protected]> I would like to request an official, binding interpretation from the WG15 concerning the following point in ISO/IEC 9945-2:1993 (POSIX.2). POSIX.2 Subclause 4.55 specifies the semantics of the "sed" utility. In subclause 4.55.7.3 the semantics of various subcommands are specified. My question has to do with the "a" and "r" subcommands. The description of the "a" subcommand states that the command [1addr]a\ <text> shall cause sed to Write <text> to standard output just before each attempt to fetch a line of input, whether by executing the N command or by beginning a new cycle. Similarly, the description of the "r" subcommand states that the command [1addr]r <file> shall cause sed to Copy the contents of <file> to standard output just before each attempt to fetch a line of input. My question has to do with the behavior of these commands on the first input line when the address is omitted. In such a case, POSIX.2 states (subclause 4.55.7.1) that A command with no addresses shall select every pattern space. If sed is executed with a script that includes an "a" command or an "r" command with no addresses, is the action of "a" or "r" taken prior to input of the first line in the input stream? My reading of the above sections of the standard is that this action should be taken prior to fetching each line, including the first one. However, it appears that existing practice is for the action of "a" or "r" to occur on each fetch attempt after the first, but not on the first. Does this behavior conform to the requirements of POSIX.2? Thank you for your attention to this matter. Interpretation response: ------------------------- The standard states the behavior for input and addressing for sed, and conforming implementations must conform to this. However, concerns have been raised about this which are being referred to the sponsor. Rationale ------------- None. Forwarded to Interpretations group: 09 Oct 94 Proposed resolution sent for review: 19th Nov 94 Resolved: 10th Dec 94