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<!-- $NetBSD: utilities.xml,v 1.1.1.1 2006/10/06 21:10:41 rillig Exp $ -->
<chapter id="utilities">
<title>Command line utilities</title>
<para>This chapter collects the various bugs and peculiarities of the
POSIX-like utilities on the platforms.</para>
<sect1 id="util.sh">
<title>sh</title>
<sect2 id="util.sh.netbsd">
<title>NetBSD</title>
<para>On NetBSD, have a look at <ulink
url="http://www.netbsd.org/cgi-bin/query-pr-list.pl?state=open&state=closed&state=feedback&text=/bin/sh&category=bin">the
various PRs</ulink> to see what's wrong with the shell.</para>
</sect2>
<sect2 id="util.sh.solaris">
<title>Solaris</title>
<para>On Solaris, <filename>/bin/sh</filename> is missing some features
that POSIX <ulink
url="http://www.opengroup.org/onlinepubs/000095399/utilities/sh.html">requires</ulink>
for the sh utility:</para>
<programlisting>
$ if ! false; then echo ok; fi
!: not found
$ echo ${PWD%/}
bad substitution
$ foo=$(true)
syntax error: `foo=$' unexpected
</programlisting>
<para>There is another sh implementation in
<filename>/usr/xpg4/bin</filename>, which implements these features.
However, many shell scripts and other programs have /bin/sh
hard-coded.</para>
<para>Another incompatibility is this:</para>
<programlisting>
$ set -- foo bar baz; echo "before: $#"; set --; echo "after: $#"
before: 3
after: 3
</programlisting>
<para>All(?) other shells, including <filename>/usr/xpg4/bin/sh</filename>,
reply with <quote>after: 0</quote>.</para>
<para>On Solaris, both <filename>/bin/sh</filename> and
<filename>/usr/xpg4/bin/sh</filename> cannot handle empty for loops.</para>
<programlisting>
$ for i in ; do echo "i=$i"; done
syntax error: `;' unexpected
</programlisting>
<para>The work-around is either to add some dummy arguments or to save
the list of things in a variable. Looping over empty lists is no
problem. But note that the various parameter expansions that are applied
here differ in this case.</para>
<programlisting>
$ things=""; for i in $things; do echo "i=$i"; done
</programlisting>
<sect3 id="util.sh.solaris.glob">
<title>Globbing problems with quoting and hidden files</title>
<programlisting>
rm -rf "testdir"
mkdir "testdir"
touch "testdir/.file"
x="."
y=".file"
echo "=== x and y quoted"
ls "$x"/*/"$y"
echo "=== only x quoted"
ls "$x"/*/$y
echo "=== nothing quoted"
ls $x/*/$y
</programlisting>
<para>The result of running this code with <filename>/bin/sh</filename>
is that in the first case, the result of the globbing expansion is
<quote><literal>./*/.file</literal></quote>, while in the two other
cases, it is the correct
<quote><literal>./testdir/.file</literal></quote>. This does only happen
when y starts with a dot, that is, for hidden files.</para>
</sect3>
</sect2>
</sect1>
<sect1 id="util.test">
<title>test</title>
<sect2 id="util.test.ext">
<title>Non-standard extensions</title>
<para>The Bourne Again Shell (Bash) allows the binary operator
<literal>==</literal> to be used as an alias for <literal>=</literal>.
This leads to problems when programs using this feature are ported to
other platforms. Furthermore, there is no apparent benefit for having
two names for the same operator.</para>
</sect2>
<sect2 id="util.test.bugs">
<title>Bugs</title>
<para>On NetBSD upto X.Y (see <ulink url="&u.PR;34646">PR 34646</ulink>), the &man.test.1; utility cannot
handle the following:</para>
<programlisting>
test ! = foo
</programlisting>
<para>POSIX <ulink
url="http://www.opengroup.org/onlinepubs/000095399/utilities/test.html">requires</ulink>
that when test is called with three arguments, the second operand is
checked first to see whether it is a binary operator. On NetBSD, the
unary <quote>!</quote> operator takes precedence.</para>
</sect2>
</sect1>
</chapter>
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