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Problem Report 0757 Details

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Report 0757 Actions

    Problem Report Number 0757
    Submitter's Classification Specification problem
    State Resolved
    Resolution Temporary Interpretation (TIN)
    Problem Resolution ID TIN.X.0048
    Raised 1970-01-01 08:00
    Updated 2003-03-13 08:00
    Published 1995-09-09 08:00
    Product Standard Commands and Utilities V2 (UNIX 95)
    Certification Program The Open Brand certification program
    Test Suite VSC version 4.1.4
    Test Identification POSIX.cmd/expr 77
    Specification Commands and Utilities Issue 4 Version 2
    Location in Spec See Problem Text
    Problem Summary TIN4C.00013 Actual output from regular expression "^^" test may be 1
    Problem Text
    The behavior of the "^" (caret) in a BRE was recently the subject of an
    IEEE interpretation (PASC Ref. #1003.2-120). The standard states that
    it is unspecified (not implementation defined) whether "^" is a special
    character in the context of the pattern being anchored to the beginning
    of the string.

    Note - our implementation does not support subexpression anchoring.
    Test Output

    Assertion #77 (A): GA114
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Note: An IEEE POSIX.2 interpretation request is pending on
    behavior of the caret (^) anchor in an expr BRE
    Testing regular expression "a^b"
    Testing regular expression "a^b"
    Testing regular expression "^^"
    expected exit status 1, got 0
    Contents of regb_err:
    output differed from expected
    Expect output: "0"
    Actual output: "1"
    Testing regular expression "^"
    Testing regular expression "[c^b]"
    Testing regular expression "[^ab]"
    Testing regular expression "[^ab]"
    Testing regular expression "[^^]"
    Testing regular expression "(a^b)"
    Testing regular expression "(a^b)"
    Testing regular expression "(^)"
    Assertion Result: FAIL

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response
    pasc-1003.2-120 asks

    Subclause 4.22.7.1 of POSIX.2 specifies the syntax and semantics of
    the expr utility. This section reads:

    The ':' matching operator shall compare the string
    resulting from the evaluation of expr1 with the BRE
    pattern resulting from the evaluation of expr2. BRE
    syntax shall be that defined in 2.8.3, except that
    all patterns are "anchored" to the beginning of the
    string (that is, only sequences starting at the first
    character of a string shall be matched by the BRE).
    Therefore, it is unspecified whether ^ is a special
    character in that context.

    Note that this description does not say that it is "implementation defined",
    but rather "unspecified" whether ^ is an anchor when used in the BRE of an
    expr matching expression. As such, this implies that a conforming
    implementation of expr need not even behave consistently from one invocation
    to the next when a ^ is used in a BRE on the right side of a ':' operator.
    Since the BRE is not a subexpression, the system defined behavior of anchors
    in subexpressions does not apply here. Is this the intention?

    The response is

    It is difficult to state what the intention was, but the standard is
    clear. If "implementation defined" were used instead of "unspecified",
    it would not affect a conforming POSIX.2 application.

    We believe this means that any behavior is acceptable in this case.

    Anticipating acceptance this propsoed resolution a temporary
    interpretation is recommended.

    Review Type SA Review
    Start Date null
    Completed null
    Status Complete
    Review Resolution Temporary Interpretation (TIN)
    Review Conclusion
    A Temporary Interpretation is granted.

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