Path: csiph.com!goblin1!goblin.stu.neva.ru!usenet.stanford.edu!not-for-mail From: Chet Ramey Newsgroups: gnu.bash.bug Subject: Re: Indices of array variables are sometimes considered unset (or just display an error). Date: Tue, 6 Nov 2018 09:44:38 -0500 Lines: 37 Approved: bug-bash@gnu.org Message-ID: References: <87va5bp5fr.fsf@gmail.com> Reply-To: chet.ramey@case.edu NNTP-Posting-Host: lists.gnu.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-Trace: usenet.stanford.edu 1541515489 11283 208.118.235.17 (6 Nov 2018 14:44:49 GMT) X-Complaints-To: action@cs.stanford.edu Cc: chet.ramey@case.edu To: Great Big Dot , bug-bash@gnu.org Envelope-to: bug-bash@gnu.org Openpgp: preference=signencrypt Autocrypt: addr=chet.ramey@case.edu; prefer-encrypt=mutual; keydata= xsDiBEEOsGwRBACFa0A1oa71HSZLWxAx0svXzhOZNQZOzqHmSuGOG92jIpQpr8DpvgRh40Yp AwdcXb8QG1J5yGAKeevNE1zCFaA725vGSdHUyypHouV0xoWwukYO6qlyyX+2BZU+okBUqoWQ koWxiYaCSfzB2Ln7pmdys1fJhcgBKf3VjWCjd2XJTwCgoFJOwyBFJdugjfwjSoRSwDOIMf0D /iQKqlWhIO1LGpMrGX0il0/x4zj0NAcSwAk7LaPZbN4UPjn5pqGEHBlf1+xDDQCkAoZ/VqES GZragl4VqJfxBr29Ag0UDvNbUbXoxQsARdero1M8GiAIRc50hj7HXFoERwenbNDJL86GPLAQ OTGOCa4W2o29nFfFjQrsrrYHzVtyA/9oyKvTeEMJ7NA3VJdWcmn7gOu0FxEmSNhSoV1T4vP2 1Wf7f5niCCRKQLNyUy0wEApQi4tSysdz+AbgAc0b/bHYVzIf2uO2lIEZQNNt+3g2bmXgloWm W5fsm/di50Gm1l1Na63d3RZ00SeFQos6WEwLUHEB0yp6KXluXLLIZitEJM0gQ2hldCBSYW1l eSA8Y2hldC5yYW1leUBjYXNlLmVkdT7CYQQTEQIAIQIbAwYLCQgHAwIDFQIDAxYCAQIeAQIX gAUCRX3FIgIZAQAKCRC7WGnwZOp0q069AKCNDRn+zzN/AHbaynls/Lvq1kH/RQCgkLvF8bDs maUHSxSIPqzlGuKWDxbOwE0EQQ6wbxAEAJCukwDigRDPhAuI+lf+6P64lWanIFOXIndqhvU1 3cDbQ/Wt5LwPzm2QTvd7F+fcHOgZ8KOFScbDpjJaRqwIybMTcIN0B2pBLX/C10W1aY+cUrXZ gXUGVISEMmpaP9v02auToo7XXVEHC+XLO9IU7/xaU98FL69l6/K4xeNSBRM/AAMHA/wNAmRB pcyK0+VggZ5esQaIP/LyolAm2qwcmrd3dZi+g24s7yjV0EUwvRP7xHRDQFgkAo6++QbuecU/ J90lxrVnQwucZmfz9zgWDkT/MpfB/CNRSKLFjhYq2yHmHWT6vEjw9Ry/hF6Pc0oh1a62USdf aKAiim0nVxxQmPmiRvtCmcJJBBgRAgAJBQJBDrBvAhsMAAoJELtYafBk6nSr43AAn2ZZFQg8 Gs/zUzvXMt7evaFqVTzcAJ0cHtKpP1i/4H4R9+OsYeQdxxWxTQ== User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 In-Reply-To: <87va5bp5fr.fsf@gmail.com> Content-Language: en-US X-Junkmail-Status: score=7/90, host=mpv2-2015.case.edu X-Junkmail-PrAS-Raw: score=7/90, refid=2.7.2:2018.11.6.140017:17:7.944, ip=, rules=__HAS_REPLYTO, __HAS_CC_HDR, __SUBJ_REPLY, __PHISH_SPEAR_SUBJ_ALERT, __BOUNCE_CHALLENGE_SUBJ, __BOUNCE_NDR_SUBJ_EXEMPT, __TO_MALFORMED_2, __TO_NAME, __TO_NAME_DIFF_FROM_ACC, __REFERENCES, __HAS_FROM, FROM_EDU_TLD, __HAS_MSGID, __SANE_MSGID, DATE_TZ_NA, __USER_AGENT, __MOZILLA_USER_AGENT, __MIME_VERSION, __IN_REP_TO, __CT, __CT_TEXT_PLAIN, __CTE, __REPLYTO_SAMEAS_FROM_ADDY, __REPLYTO_SAMEAS_FROM_ACC, __FROM_DOMAIN_IN_ANY_CC1, __FROM_DOMAIN_IN_ANY_CC2, __REPLYTO_SAMEAS_FROM_DOMAIN, __ANY_URI, __URI_WITH_PATH, __URI_NO_WWW, __CP_URI_IN_BODY, __FRAUD_MONEY_CURRENCY_DOLLAR, __SUBJ_ALPHA_NEGATE, __URI_IN_BODY, __URI_NOT_IMG, __FORWARDED_MSG, __NO_HTML_TAG_RAW, BODY_SIZE_1700_1799, BODYTEXTP_SIZE_3000_LESS, __MIME_TEXT_P1, __MIME_TEXT_ONLY, __URI_NS, HTML_00_01, HTML_00_10, __FRAUD_MONEY_CURRENCY, BODY_SIZE_5000_LESS, IN_REP_TO, MSG_THREAD, [TRUNCATED], so=2010-03-03 19:42:08, dmn=2016-08-03-0138 X-Mirapoint-Virus-RAPID-Raw: score=unknown(0), refid=str=0001.0A02020F.5BE1A8D7.00BE,ss=1,re=0.000,fgs=0, ip=0.0.0.0, so=2016-11-06 16:00:04, dmn=2011-05-27 18:58:46 X-Mirapoint-Loop-Id: c8c7db1665924556231b30cf0a600526 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.4.x-2.6.x [generic] X-Received-From: 129.22.103.227 X-BeenThere: bug-bash@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Bug reports for the GNU Bourne Again SHell List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Xref: csiph.com gnu.bash.bug:14771 On 11/5/18 4:42 PM, Great Big Dot wrote: > Description: > The parameter expansion "${!var[@]}" expands to the indices of an array > (whether linear or associative). The expansion "${var-string}" > returns "${var}" iff var is set and 'string' otherwise. These two > features do not play well together: You seem to have neglected a significant section of the documentation: "If the first character of parameter is an exclamation point (!), and parameter is not a nameref, it introduces a level of indirection. Bash uses the value formed by expanding the rest of parameter as the new parameter; this is then expanded and that value is used in the rest of the expansion, rather than the expansion of the original parameter. This is known as indirect expansion. The value is subject to tilde expansion, parameter expansion, command substitution, and arithmetic expansion. If parameter is a nameref, this expands to the name of the parameter referenced by parameter instead of performing the complete indirect expansion. The exceptions to this are the expansions of ${!prefix*} and ${!name[@]} described below. The exclamation point must immediately follow the left brace in order to introduce indirec- tion." > $ declare -a -- array=([0]='helloworld') > $ printf -- '%s\n\n' "${!array[@]-Warning: unset}" > Warning: unset This happens to "work" because there is a single array element set, and it expands to a single word. -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, UTech, CWRU chet@case.edu http://tiswww.cwru.edu/~chet/