Austin Group Defect Tracker

Aardvark Mark IV

Main | My View | View Issues | Change Log | Docs
  

Viewing Issue Simple Details [ Jump to Notes ] [ Issue History ] [ Print ]
ID Category Severity Type Date Submitted Last Update
0000717 [1003.1(2013)/Issue7+TC1] Shell and Utilities Objection Clarification Requested 2013-06-28 09:45 2019-06-10 08:55
Reporter geoffclare View Status public  
Assigned To
Priority normal Resolution Accepted As Marked  
Status Closed  
Name Geoff Clare
Organization The Open Group
User Reference
Section 2.14 exit
Page Number 2370
Line Number 75508
Interp Status Approved
Final Accepted Text See Note: 0001683.
Summary 0000717: meaning of "the shell shall exit" in a subshell environment
Description The description of the exit special built-in says that it "shall
cause the shell to exit", but it is not clear what this means when
exit is executed in a subshell environment.

The intention, and existing practice, is that the shell exits from
the subshell environment only, not the entire shell. For example:

    echo one $(exit; echo two); echo three

outputs one and three. This is consistent with the behaviour for
errors encountered by special built-ins as described in section
2.8.1 Consequences of Shell Errors (although this has some wording
problems):

    If any of the errors shown as "shall exit" or "(may) exit" occur
    in a subshell, the subshell shall (respectively may) exit with a
    non-zero status, but the script containing the subshell shall not
    exit because of the error.

There are similar problems with the use of "shall exit" in the
descriptions of the set -e and -u options. For example:

    set -e; echo one $(false; echo two); echo three
    set -u; echo one $(echo $unsetvar; echo two); echo three

also both output one and three (plus an error message in the -u case).
These can be fixed by adding an "as if" referring to exit.
Desired Action Change:

    The exit utility shall cause the shell to exit with the exit
    status specified by the unsigned decimal integer n.

to:

    The exit utility shall cause the shell to exit from its
    current execution environment with the exit status specified by
    the unsigned decimal integer n. If the current execution
    environment is a subshell environment, the shell shall exit
    from the subshell environment with the specified exit status and
    continue in the environment from which that subshell environment
    was invoked, otherwise the shell utility shall terminate with the
    specified exit status.

After page 2371 line 75546 section 2.14 exit add to EXAMPLES:

    Propagate error handling from within a subshell:
    (
        command1 || exit 1
        command2 || exit 1
        exec command3
    ) > outputfile || exit 1
    echo "outputfile created successfully"

At page 2337 line 74300 section 2.8.1 change

    If any of the errors shown as "shall exit" or "(may) exit" occur
    in a subshell, the subshell shall (respectively may) exit with a
    non-zero status, but the script containing the subshell shall not
    exit because of the error.

to

    If any of the errors shown as "shall exit" or "(may) exit" occur
    in a subshell environment, the shell shall (respectively may) exit
    from the subshell environment with a non-zero status and continue
    in the environment from which that subshell environment was invoked.

At page 2381 line 75846 section 2.14 set change:

    the shell immediately shall exit with the following exceptions

to:

    the shell immediately shall exit, as if by executing the exit
    special built-in utility with no arguments, with the following
    exceptions

At page 2382 line 75907 section 2.14 set change:

    exit status of the shell the command shall be treated as having
    been executed and returned an exit status of between 1 and 125
    inclusive. A non-interactive shell shall immediately exit.

to:

    exit status of the shell or subshell the command shall be treated
    as having been executed and returned an exit status of between 1
    and 125 inclusive. A non-interactive shell shall immediately
    exit, as if by executing the exit special built-in utility with
    no arguments.
Tags tc2-2008
Attached Files

- Relationships
related to 0000882Closed meaning of "utility syntax error" unclear 

-  Notes
(0001660)
jilles (reporter)
2013-06-30 21:06

 The part about 'set -u' does not match what the Bourne shell and ksh93 do. In most shells, a 'set -u' failure is treated like an expansion error, very similar to the one generated by the ${parameter?} expansion. Furthermore, the Bourne shell and ksh93 treat an expansion error in a redirection or assignment as a redirection or assignment error, respectively. For example,

  ksh93 -uc 'true <$x; echo continued $?'
  ksh93 -uc 'v=$x true; echo continued $?'
  ksh93 -uc '<$x; echo continued $?'

all print "continued 1" after the error message. I think this is less useful than exiting (for 'set -u' as well as ${parameter?}, arithmetic division by zero, etc.).

More commonly (also in dash and FreeBSD sh), an error inside 'command eval' or 'command .' causes the shell to continue after 'command' with a non-zero $?. This affects an error from 'set -u' but not an exit from 'set -e'. The effect of command on eval and dot is currently hardly specified and differs across shells, but that is for another issue.

Consider replacing the description of 'set -u' with:

When the shell tries to expand an unset parameter other than the ’@’ and ’*’ special parameters,
it shall write a message to standard error and the expansion shall fail.

A reference to XCU 2.8.1 Consequences of Shell Errors could be added.

The restriction on exit status in 'set -u' (must be between 1 and 125 exclusive) should then be added to "If a command fails during word expansion or redirection," in XCU 2.8.2 Exit Status for Commands.
(0001673)
geoffclare (manager)
2013-07-11 16:40
edited on: 2013-07-18 15:22

 Updated proposal which incorporates Note: 0001660...

At page 2370 line 75508 change:

    The exit utility shall cause the shell to exit with the exit
    status specified by the unsigned decimal integer n.

to:

    The exit utility shall cause the shell to exit from its
    current execution environment with the exit status specified by
    the unsigned decimal integer n. If the current execution
    environment is a subshell environment, the shell shall exit
    from the subshell environment with the specified exit status and
    continue in the environment from which that subshell environment
    was invoked, otherwise the shell utility shall terminate with the
    specified exit status.

After page 2371 line 75546 section 2.14 exit add to EXAMPLES:

    Propagate error handling from within a subshell:
    (
        command1 || exit 1
        command2 || exit 1
        exec command3
    ) > outputfile || exit 1
    echo "outputfile created successfully"

At page 2337 line 74300 section 2.8.1 change

    If any of the errors shown as "shall exit" or "(may) exit" occur
    in a subshell, the subshell shall (respectively may) exit with a
    non-zero status, but the script containing the subshell shall not
    exit because of the error.

    In all of the cases shown in the table, an interactive shell shall
    write a diagnostic message to standard error without exiting.

to:

    If any of the errors shown as "shall exit" or "(may) exit" occur
    in a subshell environment, the shell shall (respectively may) exit
    from the subshell environment with a non-zero status and continue
    in the environment from which that subshell environment was invoked.

    In all of the cases shown in the table, an interactive shell shall
    write a diagnostic message to standard error without exiting and
    without any further processing of the command in which the
    error occurred.

At page 2337 line 74312 section 2.8.2 change:

    If a command fails during word expansion or redirection, its exit
    status shall be greater than zero.

to:

    If a command fails during word expansion or redirection, its exit
    status shall be between 1 and 125 inclusive.

At page 2381 line 75846 section 2.14 set change:

    the shell immediately shall exit with the following exceptions

to:

    the shell immediately shall exit, as if by executing the exit
    special built-in utility with no arguments, with the following
    exceptions

At page 2382 line 75903 section 2.14 set change the description of
the -u option to:

    When the shell tries to expand an unset parameter other than the
    ’@’ and ’*’ special parameters, it shall write a message to
    standard error and the expansion shall fail with the
    consequences specified in 2.8.1 Consequences of Shell Errors
    (on page 2337).
(0001683)
Don Cragun (manager)
2013-07-18 15:18

 Interpretation response
------------------------
The standard is unclear on this issue, and no conformance distinction can be made between alternative implementations based on this. This is being referred to the sponsor.

Rationale:
-------------
The changes made here make the standard reflect existing practice.

Notes to the Editor (not part of this interpretation):
-------------------------------------------------------
Make the changes suggested in Note: 0001673.
(0001805)
ajosey (manager)
2013-09-06 04:54

 Interpretation Proposed 6 Sep 2013
(0001895)
ajosey (manager)
2013-10-14 13:07

 Interpretation approved 14 October 2013

- Issue History
Date Modified Username Field Change
2013-06-28 09:45 geoffclare New Issue
2013-06-28 09:45 geoffclare Name => Geoff Clare
2013-06-28 09:45 geoffclare Organization => The Open Group
2013-06-28 09:45 geoffclare Section => 2.14 exit
2013-06-28 09:45 geoffclare Page Number => 2370
2013-06-28 09:45 geoffclare Line Number => 75508
2013-06-28 09:45 geoffclare Interp Status => ---
2013-06-30 21:06 jilles Note Added: 0001660
2013-07-11 16:40 geoffclare Note Added: 0001673
2013-07-18 15:18 Don Cragun Interp Status --- => Pending
2013-07-18 15:18 Don Cragun Final Accepted Text => See Note: 0001674.
2013-07-18 15:18 Don Cragun Note Added: 0001683
2013-07-18 15:18 Don Cragun Status New => Interpretation Required
2013-07-18 15:18 Don Cragun Resolution Open => Accepted As Marked
2013-07-18 15:19 Don Cragun Final Accepted Text See Note: 0001674. => See Note: 0001683.
2013-07-18 15:19 Don Cragun Tag Attached: tc2-2008
2013-07-18 15:22 geoffclare Note Edited: 0001673
2013-09-06 04:54 ajosey Interp Status Pending => Proposed
2013-09-06 04:54 ajosey Note Added: 0001805
2013-10-14 13:07 ajosey Interp Status Proposed => Approved
2013-10-14 13:07 ajosey Note Added: 0001895
2015-03-25 12:37 geoffclare Relationship added related to 0000882
2019-06-10 08:55 agadmin Status Interpretation Required => Closed

Mantis 1.1.6[^]
Copyright © 2000 - 2008 Mantis Group
Powered by Mantis Bugtracker