[SCM] GNU Autoconf source repository branch, master, updated. v2.67-4-g14f352e

[Eric Blake]

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- Log -----------------------------------------------------------------
commit 14f352e3880538f229e423cdc3b36a717e93f7fc
Author: Eric Blake <address@hidden>
Date:   Thu Jul 29 16:21:08 2010 -0600

    docs: mention ksh file descriptor limitation
    
    * doc/autoconf.texi (File Descriptors): Document issue with fd 10
    and above.
    Reported by Ralf Wildenhues.

commit 4e7b9effeafd5c1263c66784409903dbdf526d93
Author: Eric Blake <address@hidden>
Date:   Thu Jul 29 16:10:26 2010 -0600

    docs: mention cd limitation
    
    * doc/autoconf.texi (Limitations of Builtins) <cd>: Document
    issues with empty argument.
    
    Signed-off-by: Eric Blake <address@hidden>

-----------------------------------------------------------------------

Summary of changes:
 ChangeLog         |   11 +++++++++++
 doc/autoconf.texi |   24 ++++++++++++++++++++++++
 2 files changed, 35 insertions(+), 0 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index 662a6e1..0ef1fd3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,14 @@
+2010-07-29  Eric Blake  <address@hidden>
+
+       docs: mention ksh file descriptor limitation
+       * doc/autoconf.texi (File Descriptors): Document issue with fd 10
+       and above.
+       Reported by Ralf Wildenhues.
+
+       docs: mention cd limitation
+       * doc/autoconf.texi (Limitations of Builtins) <cd>: Document
+       issues with empty argument.
+
 2010-07-29  Ralf Wildenhues  <address@hidden>
 
        Add missing index entries to manual.
diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index fac50b2..7e804a7 100644
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -15041,6 +15041,20 @@ descriptor 4 had a special use on the Stardent/Kubota 
Titan (circa
 obsolete, so it's now safe to treat file descriptors 3 and 4 like any
 other file descriptors.
 
+On the other hand, you can't portably use multi-digit file descriptors.
+Solaris @command{ksh} doesn't understand any file descriptor larger than
address@hidden:
+
address@hidden
+$ @kbd{bash -c 'exec 10>&-'; echo $?}
+0
+$ @kbd{ksh -c 'exec 9>&-'; echo $?}
+0
+$ @kbd{ksh -c 'exec 10>&-'; echo $?}
+ksh[1]: exec: 10: not found
+127
address@hidden example
+
 @node File System Conventions
 @section File System Conventions
 @cindex File system conventions
@@ -16543,6 +16557,16 @@ Also, Autoconf-generated scripts check for this 
problem when computing
 variables like @code{ac_top_srcdir} (@pxref{Configuration Actions}),
 so it is safe to @command{cd} to these variables.
 
+Posix states that behavior is undefined if @command{cd} is given an
+explicit empty argument.  Some shells do nothing, some change to the
+first entry in @env{CDPATH}, some change to @env{HOME}, and some exit
+the shell rather than returning an error.  Unfortunately, this means
+that if @samp{$var} is empty, then @samp{cd "$var"} is less predictable
+than @samp{cd $var} (at least the latter is well-behaved in all shells
+at changing to @env{HOME}, although this is probably not what you wanted
+in a script).  You should check that a directory name was supplied
+before trying to change locations.
+
 See @xref{Special Shell Variables}, for portability problems involving
 @command{cd} and the @env{CDPATH} environment variable.
 Also please see the discussion of the @command{pwd} command.


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