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IDProjectCategoryView StatusDate SubmittedLast Update
00015211003.1(2016/18)/Issue7+TC2Shell and Utilitiespublic2021-09-09 15:342022-01-06 17:26
Reporterkre Assigned To 
PrioritynormalSeverityObjectionTypeError
Status ClosedResolutionDuplicate 
NameRobert Elz
Organization
User Reference
SectionXCU 2.7.4
Page Number2362
Line Number75362-75377
Interp Status---
Final Accepted Text
Summary0001521: here document processing is underspecified
DescriptionThe specification for a Here-Document (XCU 2.7.4) is lacking
some precision, and needs to be improved.

First, there is no reason to limit the kind of file descriptor
to being a regular file, special file, or a pipe. Note that
the XBD 3.164 definition of "File" includes:

        File types include regular file, character special file, block special
        file, FIFO special file, symbolic link, socket, and directory.
        Other types of files may be supported by the implementation.

from which it appears that block/character/FIFO special files exist,
but that sockets, directories, symbolic links, and other types supported
by the implementation are not special files (though there is no actual
definition of a "special file"). While it is unlikely (to say the least)
that a symbolic link or directory would be a useful file type for a
here-document, sockets or other implementation types might be. The
wording of the standard should allow for that possibility.

Second, it is not precisely specified whether the "input lines"
which are to be stripped of tab characters are the lines in
the input, as presented to the shell, lines in the input, after
line joining (by the \<newline> combination, when that is applied)
has been carried out, or the lines to be input to the command to
which the redirection operator is applied.

Fortunately all shells seem to agree that tabs are stripped from
lines after line joining (when it applies) but before any expansions
are performed which might create more leading tab characters.

This should be precisely specified.

Third, it is not clear whether or not the end delimiter can be
formed from joined lines, or whether it must appear literally
in the input stream.

For this one shells are not in agreement, some initially treat
the end delimiter as part of the here document, and so perform
line joining, discovering the end delimiter after that, and then
removing it from the here document. Other shells look for the
end delimiter first (after joining previous lines, so a line
which looks like the end delimiter, but which is a continuation
of a previous line, will not be the end delimiter) and do not
permit it to be formed from joined lines. Since there is no
good reason for an application to ever split the end delimiter
over multiple lines in real code (as distinct from torture
tests) this can be made explicitly unspecified - applications
should not rely upon either behaviour.

Note that there is another open issue, relating to which <newline> is the
<newline> after which a here document begins, these two are orthoganal,
but this one, being simpler, should probably be processed first.
Desired ActionIn line 75364 change the words
or a pipe

to
a pipe, or some other type of file



In line 75369 change the words
shall be expanded

to
shall be expanded as the redirection operator is
performed, each time it is performed,




In lines 75374-5 change the words
stripped from input lines and the line containing
the trailing delimiter.

to
stripped from input lines after <backslash><newline>
line joining (when it applies) has been performed and the line
containing the trailing delimiter.
It is unspecified whether the line containing the trailing delimiter
is subject to this line joining in any case.
Tab stripping occurs as the here document text is read from the shell
input stream, and is not repeated after any expansions that are
required have occurred.



Please adjust the actual wording applied to be more pleasing.
TagsNo tags attached.

Relationships

duplicate of 0001036 Closed 1003.1(2013)/Issue7+TC1 Errors/Omissions in specification of here document redirection 
related to 0001043 Closed 1003.1(2013)/Issue7+TC1 Which newline starts collection of here document data? 

Activities

kre

2021-09-09 15:37

reporter   bugnote:0005497

Last edited: 2021-09-09 15:42

 Oops, sorry, I see I missed a < /em > after the > after newline...

And it should say "has been performed" not "last been performed"
No idea how my fingers came up with that one.

geoffclare

2021-09-10 08:41

manager   bugnote:0005498

I have updated the desired action to fix the problems noted in 0001521:0005497. (I removed the starting < em > rather than adding an ending < /em > as italics would be incorrect there anyway.)

geoffclare

2021-12-17 15:05

manager   bugnote:0005562

See bug 1036 0001036:0005561 for a proposed resolution.

Issue History

Date Modified Username Field Change
2021-09-09 15:34 kre New Issue
2021-09-09 15:34 kre Name => Robert Elz
2021-09-09 15:34 kre Section => XCU 2.7.4
2021-09-09 15:34 kre Page Number => 2362
2021-09-09 15:34 kre Line Number => 75362-75377
2021-09-09 15:37 kre Note Added: 0005497
2021-09-09 15:39 kre Note Edited: 0005497
2021-09-09 15:42 kre Note Edited: 0005497
2021-09-10 08:41 geoffclare Interp Status => ---
2021-09-10 08:41 geoffclare Note Added: 0005498
2021-09-10 08:41 geoffclare Desired Action Updated
2021-09-10 08:47 geoffclare Relationship added related to 0001036
2021-09-10 08:47 geoffclare Relationship added related to 0001043
2021-09-10 11:09 geoffclare Desired Action Updated
2021-12-17 15:05 geoffclare Note Added: 0005562
2022-01-06 17:24 Don Cragun Status New => Closed
2022-01-06 17:24 Don Cragun Resolution Open => Duplicate
2022-01-06 17:26 Don Cragun Relationship replaced duplicate of 0001036