I agree Paul, I wasn't sure that dash was/wasn't compliant.  It is the default with the latest Ubuntu for /bin/sh, which means busybox builds don't work on Ubuntu by default.  Since the question was raised about posix compliance, I decided to go look it up.  Here is what I found: Here are the posix specs: (free registration required) Here is the main link: <a href="http://www.unix.org/single_unix_specification/">http://www.unix.org/single_unix_specification/</a> here are some direct links: <a href="http://www.opengroup.org/onlinepubs/000095399/utilities/xcu_chap02.html#tag_02_02">http://www.opengroup.org/onlinepubs/000095399/utilities/xcu_chap02.html#tag_02_02</a> <a href="http://www.opengroup.org/onlinepubs/000095399/utilities/xcu_chap02.html#tag_02_06_03"> http://www.opengroup.org/onlinepubs/000095399/utilities/xcu_chap02.html#tag_02_06_03</a> <a href="http://www.opengroup.org/onlinepubs/000095399/utilities/echo.html">http://www.opengroup.org/onlinepubs/000095399/utilities/echo.html </a> Here are some excerpts for consideration: 2.6.3 Command Substitution "Within the backquoted style of command substitution, backslash shall retain its literal meaning, except when followed by: <tt>'$'</tt>, <tt>'`'</tt>, or <tt>'\'</tt> (dollar sign, backquote, backslash). ... A single-quoted or double-quoted string that begins, but does not end, within the <tt>"`...`"</tt> sequence produces undefined results." so a single " or ' is undefined behavior within a backquote command substitution and cannot be escaped with a backslash. echo: "It is not possible to use echo portably across all POSIX systems unless both -n (as the first argument) and escape sequences are omitted." "The following operands shall be supported: <dl compact="compact"><dt>string</dt><dd>A string to be written to standard output. If the first operand is -n, or if any of the operands contain a backslash ( <tt>'\'</tt> ) character, the results are implementation-defined.</dd><dt>... </dt><dt><tt>    \n</tt></dt><dd>Write a <newline>.</dd><dt>... </dt></dl>" So in the POSIX specs, the echo operand is not necessarily quoted, and a "\n" is SUPPOSED to be printed as a newline, unless the "-n" option is used (in which case backslash escapes are implementation specific), so according to the spec technically bash and bbox ash are non-compliant because they print the \n instead of the newline. "New applications are encouraged to use <a href="http://www.opengroup.org/onlinepubs/009695399/utilities/printf.html">printf</a> instead of echo." <h4><a name="tag_04_41_17"></a></h4>" <blockquote> The echo utility has not been made obsolescent because of its extremely widespread use in historical applications. Conforming applications that wish to do prompting without <newline>s or that could possibly be expecting to echo a -n, should use the <a href="http://www.opengroup.org/onlinepubs/009695399/utilities/printf.html">printf</a> utility derived from the Ninth Edition system. As specified, echo writes its arguments in the simplest of ways. The two different historical versions of echo vary in fatally incompatible ways. The BSD echo checks the first argument for the string -n which causes it to suppress the <newline> that would otherwise follow the final argument in the output. The System V echo does not support any options, but allows escape sequences within its operands, as described for XSI implementations in the OPERANDS section. The echo utility does not support Utility Syntax Guideline 10 because historical applications depend on echo to echo all of its arguments, except for the -n option in the BSD version. </blockquote> <h4>"</h4><h4><a name="tag_04_41_19"></a></h4><div> Regardless of all of this (or perhaps this is a good demonstration) - quoting is complicated and it is probably a good idea to avoid it when possible.  An echo "`...`" command substitution seems a little like calling "a = strtofloat(floattostr(b));" instead of directly "a=b;" On 2/3/07, Paul Fox <<a href="mailto:pgf@brightstareng.com">pgf@brightstareng.com</a>> wrote:<blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;"> vapier wrote: > On Saturday 03 February 2007, Brion Finlay wrote: > > The fix that could be made to scripts/mkconfigs in order to work more > > generally > > another fix would be to use a POSIX compliant shell ... then there wouldn't > be problem > -mike > we had the same problem with a different build system when we moved it to ubuntu.  i did some googling at the time, but couldn't find a definitive answer -- i expected to find a lot of discussion on it somewhere in ubuntu-land, since it's a pretty big change, but i didn't.  it's not clear to me that dash isn't posix compliant, at least with regard to echo's expanding '\n'. but it might not be.  is there a "dash is/isn't POSIX" discussion page out there anywhere? in our case it was expedient (and safe) to simply replace "#!/bin/sh" with "#!/bin/bash", but that's probably not appropriate for busybox. paul =--------------------- paul fox, <a href="mailto:pgf@brightstareng.com">pgf@brightstareng.com</a> _______________________________________________ busybox mailing list <a href="mailto:busybox@busybox.net">busybox@busybox.net</a> <a href="http://busybox.net/cgi-bin/mailman/listinfo/busybox">http://busybox.net/cgi-bin/mailman/listinfo/busybox</a> </blockquote></div>