xpg4_sh(1)                                                       xpg4_sh(1)

NAME
     xpg4sh - XPG4 shell

SYNTAX
     /sbin/xpg4/sh [option ...] [file] [argument ...]

DESCRIPTION
     The XPG4 shell is practically identical to the Korn shell [see
     ksh(1)]. However, since the Korn shell does not fulfill all the condi-
     tions specified by X/Open (see the CAE Specification, Commands and
     Utilities, Issue 4), a shell is also supplied under /sbin/xpg4/sh,
     which satisfies the remaining XPG4 conditions (X/Open Branding).

     The ksh Korn shell was not fully adapted to XPG4 because, in many
     cases, it should behave more like the sh Bourne shell. To prevent the
     behavior of the Korn shell from being incompatible with its previous
     behavior in such cases, the changes were carried out separately for a
     special XPG4 shell.

     The default shell (/sbin/sh) is currently linked to the Bourne shell
     (/sbin/bourne/sh). If you wish to have the XPG4 shell as the default
     shell, you need to set up the link to /sbin/xpg4/sh.

   Differences between the Korn shell and the XPG4 shell

     1. If you do not enter anything after the -o option when calling the
        shell, the XPG4 shell sends the following message to standard
        error: ksh: '': bad option(s).

        The Korn shell, however, sends the permitted options to standard
        output.

     2. In the Korn shell, time is a keyword at the start of a line (like
        if, then etc.; cf. ksh(1), section Reserved words). In the XPG4
        shell (as with the Bourne shell), on the other hand, time is a
        standard user command (/usr/bin). The following deviations regard-
        ing time can be distinguished.

        The behavior of the

        time pipeline

        command varies. In the case of the Korn shell, the pipeline com-
        mands are executed and then the elapsed time, the user and system
        time for these commands are reported as statistics to standard
        error.

        With the XPG4 shell, time is only executed for the first pipeline
        command and the statistics are output beforehand.






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xpg4_sh(1)                                                       xpg4_sh(1)

        Thus in the case of the Korn shell, if you issue the

        time ls | pg

        call, you will first see the output of ls and the pg input must
        then be performed. It is only when everything has ended that the
        statistics are output for ls and pg.

        With the XPG4 shell, the statistics are output first, followed by
        the output of ls and the input for pg.

     3. With the Korn shell, an error message is output if the echo command
        cannot write when writing to a file because the disk is full. The
        end status in this case is 1. The XPG4 shell ignores this error.

     4. The Korn shell does not lose any parameters in the following
        getopts command if the shell script is called with, for example, -l
        abc. When echo $* is called for the second time, the XPG4 shell
        only outputs -l instead of -l abc:

        #!/sbin/ksh
        set -x
        echo $*

        while getopts :l:u:t: arguments
        do
          case $arguments in
             l) ;;
             u) ;;
             t) ;;
             *) echo "wrong option \n"
             exit 1
             ;;
          esac

        done
        echo $*

     5. If an attempt is made with a read-only variable (typeset -r) to
        change the value, the Korn and XPG4 shells return the error message
        " ...: is read only".

        The difference between the two shell responses is that with the
        XPG4 shell, the error message is deliberately generated later.

     6. The Korn shell supplies the function name for a shell script func-
        tion in $0 while the XPG4 shell also supplies the name of the shell
        script.






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xpg4_sh(1)                                                       xpg4_sh(1)

        For example, in the following shell script called test.sh:

        typeset -fux dummy
        function dummy
        {
            echo $0
        }

        dummy

        The Korn shell echoes dummy, the XPG4 shell echoes test.sh.

SEE ALSO
     ksh(1), sh(1).








































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