The following issue has been SUBMITTED. ====================================================================== https://austingroupbugs.net/view.php?id=1632 ====================================================================== Reported By: kre Assigned To: ====================================================================== Project: Issue 8 drafts Issue ID: 1632 Category: Shell and Utilities Type: Clarification Requested Severity: Objection Priority: normal Status: New Name: Robert Elz Organization: User Reference: Section: XCU 2.6.1 Page Number: 2319-2320 Line Number: 74775-74794 Final Accepted Text: ====================================================================== Date Submitted: 2023-01-31 00:58 UTC Last Modified: 2023-01-31 00:58 UTC ====================================================================== Summary: Tilde expansions with HOME="" or HOME value ending in / Description: The current draft, and earlier versions, this is not a new problem, it could have been filed against any older version - but as 2.6.1 has already been updated for other reasons for Issue 8, it seemed sensible to use its most recent draft, don't specify what should happen if HOME="" or if the value of HOME ends in a '/' - including particularly, the case of HOME=/
The case of HOME=/ is perhaps most interesting, as if the text is treated literally, which almost all shells do, the result of expanding ~/foo in such a case is //foo which is an unspecified pathname (as I understand it). A recent ksh93 produces /foo from this case, but that's the only shell I can find which does (amusingly, for the case of HOME=/dir/ that version of ksh93 produces /dir//foo for ~/foo whereas an older one produces //foo for HOME=/ and /dir/foo for the HOME=/dir/ case).. mksh also makes /dir/foo in the HOME=/dir/ case and //foo in the HOME= case, most other shells simply do as the standard says, and replace the tilde prefix (just '~' here) with the value of HOME, which results in the // in both cases. This leads to the desire to use HOME="" instead of HOME=/ in the case where the home directory is intended to be the root directory, which results in ~/foo expanding to /foo in almost all shells (the now quite old FreeBSD shell I use to test with doesn't expand ~ at all when $HOME is an empty string, but that is. or quite likely was, clearly a bug, so I assume it has been fixed sometime in the past several years). However, despite the language of the standard: The pathname resulting from tilde expansion shall be treated as if quoted to prevent it being altered by field splitting and pathname expansion. most shells expand a word which is just ~ to nothing if HOME='' rather than (effectively) to "" which that sentence seems to require. Only bash, the NetBSD shell, and the older version of ksh93 made "". (Again, the FreeBSD shell just produces ~ here, for the same reason as above). This all needs to be cleaned up. Desired Action: I'd suggest requiring that if a pathname resulting from a tilde espansion (a term which really ought be better defined - I assume that in ~/foo where HOME=/dir that the pathname intended is "/dir" not "/dir/foo" otherwise ~/*.c would never be able to work) ends in a / that if a / occurs as the next character of the word containing the tilde expansion be omitted from the result - as that produces better results overall (despite it going to require changes in most shells, including the one I maintain). I'd also suggest being more explicit either than when HOME='' ~ expands to "" or nothing (it makes no difference if there is more to the word). For this, I'd prefer "" (for both the obvious reason, and because it is more consistemt with both the current wording, and useful behaviour). ====================================================================== Issue History Date Modified Username Field Change ====================================================================== 2023-01-31 00:58 kre New Issue 2023-01-31 00:58 kre Name => Robert Elz 2023-01-31 00:58 kre Section => XCU 2.6.1 2023-01-31 00:58 kre Page Number => 2319-2320 2023-01-31 00:58 kre Line Number => 74775-74794 ======================================================================
