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Problem Report 0751 Details

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Report 0751 Actions

    Problem Report Number 0751
    Submitter's Classification Specification problem
    State Resolved
    Resolution Temporary Interpretation (TIN)
    Problem Resolution ID TIN.X.0042
    Raised 1970-01-01 08:00
    Updated 2003-03-13 08:00
    Published 1995-10-23 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 60 65 99 100 102 105 107 108 109 110 114 120 125
    Specification Commands and Utilities Issue 4 Version 2
    Location in Spec See Problem Text
    Problem Summary TIN4C.00019 The tests may fail on implementations that adhere to
    historic practice and generate an empty line instead of nothing.
    Problem Text The tests may fail on implementations that adhere to historic
    practice and generate an empty line instead of nothing.
    Although
    POSIX.2 interpretation #105 reaffirms the behavior, the POSIX.2b
    draft reinstates the historic behavior.

    The tests shown all depend on the output of expr when an attempt
    is
    made to match a string using the subexpression syntax and the
    matched
    string is a null string (i.e. there is no match). In this case,
    POSIX.2 states (and XCU4 repeats):

    The character '0' shall be written to indicate a zero
    value and nothing shall be written to indicate a null
    string.

    (POSIX.2 subclause 4.22.6.1.) This differs from historic
    practice. An
    IEEE Interpretation Request was made regarding this issue, and
    the
    resolution of this request was:

    The standard is clear that a nl is not appended to the
    results of
    the evaluation in any case. This is not historical
    behavior,
    however, conforming implementations must conform to this.
    However,
    concerns have been raised about this which are being
    referred to
    the sponsor.

    (The complete text of the interpretation request and response
    are
    attached.) In view of the last sentence, as well as the fact
    that
    this differs from historic practice, a waiver is appropriate.
    Moreover,
    in the most recent draft of POSIX.2b, the language has been
    changed to
    require the historic behavior.

    Here is the text of IEEE Interpretation pasc-1003.2-105:
    -----------------start of interpretation-------------------

    _____________________________________________________________________________
    (c) 1995 The Institute of Electrical and Electronic Engineers,
    Inc.
    Not to be published without prior written permission of the
    IEEE.

    _____________________________________________________________________________

    To: Chuck Hickey
    From: Andrew Josey, PASC Interpretations Vice-Chair
    Reference: PASC 1003.2-92 #105


    Dear Sir.

    Subject: IEEE Standard 1003.2-1992

    Enclosed is the official response for your request for an
    interpretation
    of IEEE Standard 1003.2-1992:
    Topic: expr standard output
    representing a null string
    Relevant Sections: 4.22.6.1

    This response was developed and approved by the members of the
    1003.2
    Interpretations Committee.

    Please can you confirm receipt of this electronic mail message
    within ten working days, please carbon copy your response to the
    IEEE
    (stds.pasc-ieee-officers@ieee.org)

    Sincerely,


    Andrew Josey
    PASC VC Interpretations

    Enclosures


    Cc: IEEE PASC Officers
    Don Cragun, Chair, P1003.2


    _____________________________________________________________________________
    (c) 1995 The Institute of Electrical and Electronic Engineers,
    Inc.
    Not to be published without prior written permission of the
    IEEE.





    _____________________________________________________________________________
    PASC
    Interpretation reference

    1003.2-92 #105


    _____________________________________________________________________________

    Interpretation Number: XXXX
    Topic: expr standard output
    representing a null string
    Relevant Sections: 4.22.6.1

    Interpretation Request:
    -----------------------

    Date: Tue, 4 Apr 1995 17:37:40 -0700
    From: Chuck.Hickey@Eng.Sun.COM (Chuck Hickey
    [CONTRACTOR])

    Dear Standards Board,
    I would like to request a formal interpretation on the
    following
    issue concerning the expr utility in POSIX.2.

    Standard: IEEE Std 1003.2-1992
    Topic: expr standard output representing a null
    string
    Relevant Sections: 4.22.6.1

    In IEEE Std 1003.2-1992 section 4.22.6.1 (Standard
    Output of
    the expr utility), P276, L4127-4129, the description of
    the
    standard output representing expressions evaluating to
    zero and
    to null strings is:
    The character '0' shall be written to indicate a
    zero
    value and nothing shall be written to indicate a
    null
    string.

    This could be interpreted literally to mean that the
    output in
    these two cases must not include a newline character.
    (At
    least one developer of a POSIX.2 test suite has used
    this
    interpretation for the null string, but not for '0'.)

    In both BSD and System V historic practice, an
    expression
    evaluating to zero produced "0
    " on standard output and
    an
    expression evaluating to a null string produced an empty
    line
    on standard output.

    The rationale in section E.4.22, P904, L6209-6213
    acknowledges
    that expr could be replaced by other shell constructs in
    the
    POSIX.2 shell, but says the utility was kept because of
    the
    many historical shell scripts that use it. The
    rationale also
    mentions that other changes in early drafts of the
    standard
    were backed out because they weren't historic practice
    (see L6229-6230). It seems strange that this change to
    historical practice was not documented if it was
    intentional.

    To match historic BSD and System V implementations, the
    second sentence of the Standard Output section on P276,
    L4128-2129 should have been something like:
    An empty line shall be written to indicate a
    null string.
    Note that the zero case is already handled in the first
    sentence
    in that section.

    Was this change to historic practice intentional?




    Interpretation response
    ------------------------
    The standard is clear that a nl is not appended to the results
    of the
    evaluation in any case. This is not historical behavior,
    however,
    conforming implementations must conform to this. However,
    concerns
    have been raised about this which are being referred to the
    sponsor.



    Rationale:
    None
    Proposed resolution circulated: May 16th
    Comments due: June 15th
    Finalised: June 16th 1995

    ------------------end of interpretation--------------------
    Test Output -----------------start of test output------------------


    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #60 (A): subexpressions extracted via ( and )'
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Actual output differs from expected.
    diff of "expr_actual" and "expr_eso":
    *** expr_actual Tue Sep 5 16:12:50 1995
    --- expr_eso Tue Sep 5 16:12:50 1995
    ***************
    *** 1 ****
    -
    --- 0 ----

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #65 (A): GA102
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Testing regular expression "b*"
    output differed from expected
    Expect output: ""
    Actual output: ""

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #99 (A): GA136
    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
    the validity of the regular expression used in the third test
    of this assertion.
    Testing regular expression "(a(b(c(d(e)))))4"
    Testing regular expression "a(b)*c1"
    output differed from expected
    Expect output: ""
    Actual output: ""
    Testing regular expression
    "(a(b(c(d(e(f(g)h(i(j))))))))9"
    Testing regular expression "a(b)*c"
    output differed from expected
    Expect output: ""
    Actual output: ""

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #100 (A): GA137
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Testing regular expression "a(b)*c1"
    output differed from expected
    Expect output: ""
    Actual output: ""

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #102 (A): GA139
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Testing regular expression "(ag*b)"
    Testing regular expression "(a.*b)"
    Testing regular expression "a(b*c)"
    Testing regular expression "a(bbb*c)"
    Testing regular expression "(a(b)*c2)"
    Testing regular expression "(a(b)*c2)"
    output differed from expected
    Expect output: ""
    Actual output: ""
    Testing regular expression "(([a-c]*)2)"
    output differed from expected
    Expect output: ""
    Actual output: ""
    Testing regular expression "(([a-c]*)2)"
    Testing regular expression "(a^*b)"
    Testing regular expression "(a^*b)"

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #105 (A): GA142
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Testing regular expression "([a-c]*){0,}"
    Testing regular expression "([a-c]*){2,}"
    output differed from expected
    Expect output: ""
    Actual output: ""
    Testing regular expression "(a{1,255})"

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #107 (A): GA144
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Testing regular expression "^[[[.].]](1)\*{1,2}$"
    Testing regular expression
    "[[=*=]][[==]][[=]=]][[===]][[...]][[:punct:]]"
    Testing regular expression "[$(*)^]*"
    Testing regular expression "[1]"
    Testing regular expression "[{1,2}]"
    Testing regular expression "(*)2*"
    output differed from expected
    Expect output: ""
    Actual output: ""
    Testing regular expression "(a(b{1,2})){1,2}"
    Testing regular expression "(a)2"
    Testing regular expression "ab*"
    Testing regular expression "ab{2,4}"

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #108 (A): GA146
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Testing regular expression "(^a)1"
    output differed from expected
    Expect output: ""
    Actual output: ""
    Testing regular expression "(^^a)"
    output differed from expected
    Expect output: ""
    Actual output: ""
    Testing regular expression "(^a)1"
    Testing regular expression "(^^)"

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #109 (A): GA147
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Testing regular expression ".*(a)$"
    Testing regular expression "(a)$"
    output differed from expected
    Expect output: ""
    Actual output: ""
    Testing regular expression "99ZZ([a-z]*)$"
    Testing regular expression "99ZZ([a-z]*)$"
    output differed from expected
    Expect output: ""
    Actual output: ""

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #110 (A): GA148
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Testing regular expression "(a$)1"
    output differed from expected
    Expect output: ""
    Actual output: ""
    Testing regular expression "(a$)1"
    Testing regular expression "(ab$)"
    output differed from expected
    Expect output: ""
    Actual output: ""
    Testing regular expression "(ab$)"

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #114 (A):
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Actual output differs from expected.
    diff of "expr_actual" and "expr_eso":
    *** expr_actual Tue Sep 5 16:24:19 1995
    --- expr_eso Tue Sep 5 16:24:19 1995
    ***************
    *** 1 ****
    -
    --- 0 ----

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #120 (A):
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Standard output isn't empty
    Contents of out.stdout:

    ************************************************************************



    ************************************************************************
    /tset/POSIX.cmd/expr/expr.ex 1 Failed


    Test Information:
    Assertion #125 (A): GA44
    Note: An IEEE POSIX.2 interpretation request is pending on
    'nothing will be written to indicate a null string'.
    Actual output differs from expected.
    diff of "expr_actual" and "expr_eso":
    *** expr_actual Tue Sep 5 16:24:39 1995
    --- expr_eso Tue Sep 5 16:24:39 1995
    ***************
    *** 1 ****
    -
    --- 0 ----

    ************************************************************************

    Review Information

    Review Type TSMA Review
    Start Date null
    Completed null
    Status Complete
    Review Recommendation No Resolution Given
    Review Response Anticipating acceptance of the modified expr specification
    in POSIX 2003.2b/D11 and the eventual alignment of the tests
    with it
    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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