Nabble - Gnu - Bash

Re: functions can be created with dotted name but not removed

2009-12-04T20:55:11Z

Michael O'Donnell wrote:

> Bash Version: 4.0
> Patch Level: 28
> Release Status: release
>
> Description:
>
> A bash function with a dot in its name can be created and used with no
> problems but cannot be removed - the "unset" command chokes on the name.

It's true -- the shell allows you to define a function with an invalid
name containing a dot (in retrospect, probably not the wisest choice).
Since `unset' without options assumes it is unsetting a variable, and
bash doesn't allow you to create a variable whose name contains a dot,
you need to tell unset you're removing a function: `unset -f f.dot'.

Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU chet@... http://cnswww.cns.cwru.edu/~chet/

Re: Options for IPC between bash processes under cygwin

2009-12-04T17:49:15Z

Oh, cool. Thanks for correcting me!

jon.

On Sat, Dec 5, 2009 at 11:54 AM, Eric Blake <ebb9@...> wrote:

> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> According to Jon Seymour on 12/4/2009 4:00 PM:
>> On Linux or any reasonable OS, I could do this remote dispatch easily
>> with named pipes, but these don't exist on cygwin.
>
> That's where you're wrong. Named pipes DO exist on cygwin, although there
> are still some bugs being hammered out when trying to have multiple
> simultaneous writers to a named pipe. Also, whereas you can do <>pipe on
> Linux, that won't work on cygwin (where named pipes must be read-only owr
> write-only).
>
> - --
> Don't work too hard, make some time for fun as well!
>
> Eric Blake ebb9@...
> -----BEGIN PGP SIGNATURE-----
> Version: GnuPG v1.4.9 (Cygwin)
> Comment: Public key at home.comcast.net/~ericblake/eblake.gpg
> Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/
>
> iEYEARECAAYFAksZr0AACgkQ84KuGfSFAYBnbgCeMS9E6jFwocHi4WbOBKk+OTmH
> G/0AoNZjXu/8oytboSqzbX2VIW9i1UIb
> =PKzk
> -----END PGP SIGNATURE-----
>

Re: Options for IPC between bash processes under cygwin

2009-12-04T16:54:11Z

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA1

According to Jon Seymour on 12/4/2009 4:00 PM:
> On Linux or any reasonable OS, I could do this remote dispatch easily
> with named pipes, but these don't exist on cygwin.

That's where you're wrong. Named pipes DO exist on cygwin, although there
are still some bugs being hammered out when trying to have multiple
simultaneous writers to a named pipe. Also, whereas you can do <>pipe on
Linux, that won't work on cygwin (where named pipes must be read-only owr
write-only).

- --
Don't work too hard, make some time for fun as well!

Eric Blake ebb9@...
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v1.4.9 (Cygwin)
Comment: Public key at home.comcast.net/~ericblake/eblake.gpg
Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/

iEYEARECAAYFAksZr0AACgkQ84KuGfSFAYBnbgCeMS9E6jFwocHi4WbOBKk+OTmH
G/0AoNZjXu/8oytboSqzbX2VIW9i1UIb
=PKzk
-----END PGP SIGNATURE-----

Re: functions can be created with dotted name but not removed

2009-12-04T15:21:33Z

On Dec 4, 9:25 am, "Michael O'Donnell" <mod.bash...@...> wrote:

> Configuration Information [Automatically generated, do not change]:
> Machine: i486
> OS: linux-gnu
> Compiler: gcc
> Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='i486' -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i486-pc-linux-gnu' -DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H -I. -I../bash -I../bash/include -I../bash/lib -g -O2 -Wall
> uname output: Linux e521 2.6.30-2-686 #1 SMP Sat Sep 26 01:16:22 UTC 2009 i686 GNU/Linux
> Machine Type: i486-pc-linux-gnu
>
> Bash Version: 4.0
> Patch Level: 28
> Release Status: release
>
> Description:
>
> A bash function with a dot in its name can be created and used with no
> problems but cannot be removed - the "unset" command chokes on the name.
>
> Repeat-By:
>
> This sequence yields the expected results:
>
> function f() { echo $FUNCNAME ; }
> f
> unset f
>
> ...while this sequence fails during the unset phase with the complaint
> that the name is not a valid identifier:
>
> function f.dot() { echo $FUNCNAME ; }
> f.dot
> unset f.dot

I can confirm that this behavior is also present in 3.2.49(23)-release
and 4.0.33(1)-release.

Options for IPC between bash processes under cygwin

2009-12-04T15:00:05Z

I'd like to dispatch commands from one light-weight bash process to a
longer running bash process which takes longer to initialize [ I have
a _big_ library of bash functions ].

On Linux or any reasonable OS, I could do this remote dispatch easily
with named pipes, but these don't exist on cygwin.

I'd be interested to know if there are any good solutions to this
problem already in existence.

jon.

Re: functions can be created with dotted name but not removed

2009-12-04T14:10:40Z

Michael O'Donnell wrote:

> A bash function with a dot in its name can be created and used with no
> problems but cannot be removed - the "unset" command chokes on the name.
>
>
> Repeat-By:
>
> This sequence yields the expected results:
>
> function f() { echo $FUNCNAME ; }
> f
> unset f
>
> ...while this sequence fails during the unset phase with the complaint
> that the name is not a valid identifier:
>
> function f.dot() { echo $FUNCNAME ; }
> f.dot
> unset f.dot

Try

unset -f f.dot

Re: output redirection with process substitution asynchronous?

2009-12-04T11:18:44Z

On Dec 4, 12:58 pm, pk <p...@...> wrote:

> pjodrr wrote:
> > Hello,
>
> > how can I prefix every line of output of some command with a
> > timestamp? I thought like this:
>
> > $ exec 3> >(while read line; do echo "$(date): $line"; done)
> > $ seq 4 >&3
> > Friday, December 4, 2009 4:20:29 PM MET: 1
> > $ Friday, December 4, 2009 4:20:29 PM MET: 2
> > Friday, December 4, 2009 4:20:29 PM MET: 3
> > Friday, December 4, 2009 4:20:29 PM MET: 4
>
> > please note that the prompt ($) returns before the command completes.
> > Why is the
> > process substitution asynchronous?
> > Does anybody know of a better way to accomplish this?
>
> What's wrong with
>
> seq 4 | while read line; do echo "$(date): $line"; done

It works for me. Does it not for you? If you're asking why not do it,
then the answer is "why call an external program unnecessarily?".

Sorry, by the way, I missed what you were doing with the file
descriptor on my first read. What is it that you're trying to
accomplish? Are you doing this only to number the lines or is either
seq or the while loop a stand-in for something else?

Re: output redirection with process substitution asynchronous?

2009-12-04T10:58:14Z

pjodrr wrote:

> Hello,
>
> how can I prefix every line of output of some command with a
> timestamp? I thought like this:
>
> $ exec 3> >(while read line; do echo "$(date): $line"; done)
> $ seq 4 >&3
> Friday, December 4, 2009 4:20:29 PM MET: 1
> $ Friday, December 4, 2009 4:20:29 PM MET: 2
> Friday, December 4, 2009 4:20:29 PM MET: 3
> Friday, December 4, 2009 4:20:29 PM MET: 4
>
> please note that the prompt ($) returns before the command completes.
> Why is the
> process substitution asynchronous?
> Does anybody know of a better way to accomplish this?

What's wrong with

seq 4 | while read line; do echo "$(date): $line"; done

Re: output redirection with process substitution asynchronous?

2009-12-04T10:46:37Z

On Dec 4, 9:28 am, pjodrr <pjo...@...> wrote:

This should be in gnu.bash rather than gnu.bash.bug

Would this work for you?

while read line; do echo "$(date): $line $((num++))"; done

output redirection with process substitution asynchronous?

2009-12-04T07:28:07Z

Hello,

how can I prefix every line of output of some command with a
timestamp? I thought like this:

$ exec 3> >(while read line; do echo "$(date): $line"; done)
$ seq 4 >&3
Friday, December 4, 2009 4:20:29 PM MET: 1
$ Friday, December 4, 2009 4:20:29 PM MET: 2
Friday, December 4, 2009 4:20:29 PM MET: 3
Friday, December 4, 2009 4:20:29 PM MET: 4

please note that the prompt ($) returns before the command completes.
Why is the
process substitution asynchronous?
Does anybody know of a better way to accomplish this?

Thanks,

Peter

functions can be created with dotted name but not removed

2009-12-04T07:26:28Z

Configuration Information [Automatically generated, do not change]:
Machine: i486
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS: -DPROGRAM='bash' -DCONF_HOSTTYPE='i486' -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='i486-pc-linux-gnu' -DCONF_VENDOR='pc' -DLOCALEDIR='/usr/share/locale' -DPACKAGE='bash' -DSHELL -DHAVE_CONFIG_H -I. -I../bash -I../bash/include -I../bash/lib -g -O2 -Wall
uname output: Linux e521 2.6.30-2-686 #1 SMP Sat Sep 26 01:16:22 UTC 2009 i686 GNU/Linux
Machine Type: i486-pc-linux-gnu

Bash Version: 4.0
Patch Level: 28
Release Status: release

Description:

A bash function with a dot in its name can be created and used with no
problems but cannot be removed - the "unset" command chokes on the name.

Repeat-By:

This sequence yields the expected results:

function f() { echo $FUNCNAME ; }
f
unset f

...while this sequence fails during the unset phase with the complaint
that the name is not a valid identifier:

function f.dot() { echo $FUNCNAME ; }
f.dot
unset f.dot

functions can be created with dotted name but not removed

2009-12-04T07:25:53Z

RFC: Letting bash print an XML syntax dump

2009-12-04T01:46:45Z

Hi, bash folks,

for a larger shell-based project I wanted to have definit answers to questions like

- are all redirections to log handle 3 done when the log handle is actually open?
- are all calls to grep handled properly (either return value or output ignored)?
- are all calls to exit valid?

Parsing shell syntax by means of Perl regexps turned to out to be hard and unreliable.

So I added a new bash commandline option '--dump-syntax' that lets bash dump an XML-based syntax tree of the input script. The rest of the job was relatively easy using Perl and Perl-based XPath queries. (As a side-effect, bash also checks the syntax of process and command substitutions, what option "-n" would not do.) And now that I have my bashlint perl script I start getting adicted to it - every time I come across a stupid bug in my code I start thinking how bashlint could have detected that bug.

I work for a closed-source software company and I would need extra paperwork to release the (bash-4.0-based) patch under the GPL. I already asked the bash maintainer (who found the idea interesting) and he proposed to ask the bash society for feedback before starting the paperwork.

Please let me know what you think.

Regards

Jens

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<w text="-ne"/>
<w text="0"/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<seq>
<simple line="195">
<w text="echo"/>
<w text=""$prog: could not touch $filename""/>
<redirect type="dupout" from="1" to="2"/>
</simple>
<simple line="196">
<a name="exitcode" text="4"/>
</simple>
<simple line="197">
<w text="continue"/>
</simple>
</seq>
</ifthen>
</if>
<simple line="199">
<w text="fixfile"/>
<w text=""$filename""/>
</simple>
</seq>
</ifthen>
</if>
<simple line="201">
<w text="continue"/>
</simple>
</seq>
</ifthen>
</if>
<simple line="206">
<a name="savedir" text="`dirname -- "$filename"`">
<simple line="1">
<w text="dirname"/>
<w text="--"/>
<w text=""$filename""/>
</simple>
</a>
</simple>
<if>
<ifcond>
<simple line="207">
<w text="["/>
<w text="-z"/>
<w text=""$savedir""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<simple line="208">
<a name="savedir" text="."/>
</simple>
</ifthen>
</if>
<case>
<caseword>
<w text=""$rolldir""/>
</caseword>
<casetest>
<w text="/*"/>
</casetest>
<casebody>
<simple line="212">
<a name="savedir" text=""$rolldir""/>
</simple>
</casebody>
<casetest>
<w text="*"/>
</casetest>
<casebody>
<simple line="215">
<a name="savedir" text=""$savedir/$rolldir""/>
</simple>
</casebody>
</case>
<if>
<ifcond>
<simple line="218">
<w text="["/>
<w text="!"/>
<w text="-d"/>
<w text=""$savedir""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<seq>
<simple line="219">
<w text="mkdir"/>
<w text="-p"/>
<w text="--"/>
<w text=""$savedir""/>
</simple>
<if>
<ifcond>
<simple line="220">
<w text="["/>
<w text=""$?""/>
<w text="-ne"/>
<w text="0"/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<seq>
<simple line="221">
<w text="echo"/>
<w text=""$prog: could not mkdir $savedir""/>
<redirect type="dupout" from="1" to="2"/>
</simple>
<simple line="222">
<a name="exitcode" text="5"/>
</simple>
<simple line="223">
<w text="continue"/>
</simple>
</seq>
</ifthen>
</if>
<simple line="225">
<w text="chmod"/>
<w text="0755"/>
<w text="--"/>
<w text=""$savedir""/>
</simple>
</seq>
</ifthen>
</if>
<if>
<ifcond>
<simple line="227">
<w text="["/>
<w text="!"/>
<w text="-w"/>
<w text=""$savedir""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<seq>
<simple line="228">
<w text="echo"/>
<w text=""$prog: directory $savedir is not writable""/>
<redirect type="dupout" from="1" to="2"/>
</simple>
<simple line="229">
<a name="exitcode" text="7"/>
</simple>
<simple line="230">
<w text="continue"/>
</simple>
</seq>
</ifthen>
</if>
<simple line="234">
<a name="newname" text="`basename -- "$filename"`">
<simple line="1">
<w text="basename"/>
<w text="--"/>
<w text=""$filename""/>
</simple>
</a>
</simple>
<simple line="235">
<a name="newname" text=""$savedir/$newname""/>
</simple>
<simple line="238">
<a name="cycle" text="$(( $count - 1))"/>
</simple>
<simple line="239">
<w text="rm"/>
<w text="-f"/>
<w text="--"/>
<w text=""$newname.$cycle""/>
<w text=""$newname.$cycle$DOT_Z""/>
</simple>
<while>
<loopcond>
<simple line="240">
<w text="["/>
<w text="$cycle"/>
<w text="-gt"/>
<w text="1"/>
<w text="]"/>
</simple>
</loopcond>
<loopbody>
<seq>
<simple line="242">
<a name="oldcycle" text="$cycle"/>
</simple>
<simple line="243">
<a name="cycle" text="$(( $cycle - 1 ))"/>
</simple>
<if>
<ifcond>
<simple line="245">
<w text="["/>
<w text="-f"/>
<w text=""$newname.$cycle$DOT_Z""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<simple line="246">
<w text="mv"/>
<w text="-f"/>
<w text="--"/>
<w text=""$newname.$cycle$DOT_Z""/>
<w text=""$newname.$oldcycle$DOT_Z""/>
</simple>
</ifthen>
</if>
<if>
<ifcond>
<simple line="249">
<w text="["/>
<w text="-f"/>
<w text=""$newname.$cycle""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<simple line="251">
<w text="mv"/>
<w text="-f"/>
<w text="--"/>
<w text=""$newname.$cycle""/>
<w text=""$newname.$oldcycle""/>
</simple>
</ifthen>
</if>
</seq>
</loopbody>
</while>
<if>
<ifcond>
<simple line="256">
<w text="["/>
<w text="-f"/>
<w text=""$newname.0""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<seq>
<if>
<ifcond>
<simple line="257">
<w text="["/>
<w text="-z"/>
<w text=""$COMPRESS""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<seq>
<simple line="258">
<a name="newfile" text=""$newname.1""/>
</simple>
<simple line="259">
<w text="mv"/>
<w text="--"/>
<w text=""$newname.0""/>
<w text=""$newfile""/>
</simple>
</seq>
</ifthen>
<ifelse>
<seq>
<simple line="261">
<a name="newfile" text=""$newname.1$DOT_Z""/>
</simple>
<simple line="264">
<w text="$COMPRESS"/>
<w text="$COMPRESS_OPTS"/>
<w text=""$newname.0""/>
</simple>
<simple line="265">
<w text="mv"/>
<w text="--"/>
<w text=""$newname.0$DOT_Z""/>
<w text=""$newfile""/>
</simple>
</seq>
</ifelse>
</if>
<simple line="267">
<w text="fixfile"/>
<w text=""$newfile""/>
</simple>
</seq>
</ifthen>
</if>
<if>
<ifcond>
<and>
<simple line="271">
<w text="test"/>
<w text="-n"/>
<w text=""$datum""/>
</simple>
<simple line="271">
<w text="test"/>
<w text="-n"/>
<w text=""$COMPRESS""/>
</simple>
</and>
</ifcond>
<ifthen>
<simple line="272">
<w text="$COMPRESS"/>
<w text="$COMPRESS_OPTS"/>
<w text="--"/>
<w text=""$newname".[0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9][0-9]"/>
</simple>
</ifthen>
</if>
<if>
<ifcond>
<simple line="276">
<w text="["/>
<w text="-n"/>
<w text=""$forceclean""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<seq>
<simple line="277">
<a name="cycle" text="$(( $count - 1))"/>
</simple>
<if>
<ifcond>
<simple line="278">
<w text="["/>
<w text="-z"/>
<w text=""$COMPRESS""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<simple line="279">
<w text="rm"/>
<w text="-f"/>
<w text="--"/>
<w text="`ls -t -- $newname.[0-9]* | sed -e 1,${cycle}d`">
<pipe>
<simple line="1">
<w text="ls"/>
<w text="-t"/>
<w text="--"/>
<w text="$newname.[0-9]*"/>
</simple>
<simple line="1">
<w text="sed"/>
<w text="-e"/>
<w text="1,${cycle}d"/>
</simple>
</pipe>
</w>
</simple>
</ifthen>
<ifelse>
<simple line="281">
<w text="rm"/>
<w text="-f"/>
<w text="--"/>
<w text="`ls -t -- $newname.[0-9]*$DOT_Z | sed -e 1,${cycle}d`">
<pipe>
<simple line="1">
<w text="ls"/>
<w text="-t"/>
<w text="--"/>
<w text="$newname.[0-9]*$DOT_Z"/>
</simple>
<simple line="1">
<w text="sed"/>
<w text="-e"/>
<w text="1,${cycle}d"/>
</simple>
</pipe>
</w>
</simple>
</ifelse>
</if>
</seq>
</ifthen>
</if>
<if>
<ifcond>
<simple line="286">
<w text="["/>
<w text="-n"/>
<w text=""$preserve""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<seq>
<sub>
<seq>
<simple line="287">
<w text="umask"/>
<w text="077"/>
</simple>
<simple line="288">
<w text="touch"/>
<w text="--"/>
<w text=""$filename.new""/>
</simple>
<simple line="289">
<w text="chown"/>
<w text="--reference="$filename""/>
<w text="--"/>
<w text=""$filename.new""/>
</simple>
<simple line="290">
<w text="chmod"/>
<w text="--reference="$filename""/>
<w text="--"/>
<w text=""$filename.new""/>
</simple>
</seq>
</sub>
<simple line="291">
<a name="filenew" text="1"/>
</simple>
</seq>
</ifthen>
<ifcond>
<simple line="292">
<w text="["/>
<w text="-n"/>
<w text=""$touch$user$group$mode""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<seq>
<simple line="293">
<w text="touch"/>
<w text="--"/>
<w text=""$filename.new""/>
</simple>
<simple line="294">
<w text="fixfile"/>
<w text=""$filename.new""/>
</simple>
<simple line="295">
<a name="filenew" text="1"/>
</simple>
</seq>
</ifthen>
</if>
<simple line="298">
<a name="newfilename" text=""$newname.0""/>
</simple>
<if>
<ifcond>
<simple line="300">
<w text="["/>
<w text="-f"/>
<w text=""$filename""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<if>
<ifcond>
<simple line="301">
<w text="["/>
<w text="-n"/>
<w text=""$filenew""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<if>
<ifcond>
<simple line="302">
<w text="ln"/>
<w text="-f"/>
<w text="--"/>
<w text=""$filename""/>
<w text=""$newfilename""/>
</simple>
</ifcond>
<ifthen>
<simple line="303">
<w text="mv"/>
<w text="--"/>
<w text=""$filename.new""/>
<w text=""$filename""/>
</simple>
</ifthen>
<ifelse>
<seq>
<simple line="305">
<w text="echo"/>
<w text=""Error hardlinking $filename to $newfilename""/>
<redirect type="dupout" from="1" to="2"/>
</simple>
<simple line="306">
<a name="exitcode" text="8"/>
</simple>
<simple line="307">
<w text="continue"/>
</simple>
</seq>
</ifelse>
</if>
</ifthen>
<ifelse>
<simple line="310">
<w text="mv"/>
<w text="--"/>
<w text=""$filename""/>
<w text=""$newfilename""/>
</simple>
</ifelse>
</if>
</ifthen>
</if>
<and>
<simple line="313">
<w text="["/>
<w text="!"/>
<w text="-f"/>
<w text=""$newfilename""/>
<w text="]"/>
</simple>
<simple line="313">
<w text="touch"/>
<w text="--"/>
<w text=""$newfilename""/>
</simple>
</and>
<simple line="314">
<w text="fixfile"/>
<w text=""$newfilename""/>
</simple>
<if>
<ifcond>
<simple line="315">
<w text="["/>
<w text="-n"/>
<w text=""$datum""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<seq>
<simple line="316">
<w text="mv"/>
<w text="--"/>
<w text=""$newfilename""/>
<w text=""$newname.$DATUM""/>
</simple>
<simple line="317">
<a name="newfilename" text=""$newname.$DATUM""/>
</simple>
</seq>
</ifthen>
</if>
<if>
<ifcond>
<simple line="320">
<w text="["/>
<w text="-n"/>
<w text=""$hookscript""/>
<w text="]"/>
</simple>
</ifcond>
<ifthen>
<or>
<simple line="321">
<a name="FILE" text=""$newfilename""/>
<w text="$SHELL"/>
<w text="-c"/>
<w text=""$hookscript""/>
</simple>
<group>
<seq>
<simple line="323">
<a name="ret" text="$?"/>
</simple>
<or>
<simple line="324">
<w text="test"/>
<w text=""$quiet""/>
<w text="-eq"/>
<w text="1"/>
</simple>
<simple line="324">
<w text="echo"/>
<w text=""Hook script failed with exit code $ret.""/>
<redirect type="dupout" from="1" to="2"/>
</simple>
</or>
</seq>
</group>
</or>
</ifthen>
</if>
<or>
<simple line="329">
<w text="test"/>
<w text=""$quiet""/>
<w text="-eq"/>
<w text="1"/>
</simple>
<simple line="329">
<w text="echo"/>
<w text=""Rotated \`$filename' at `date`."">
<simple line="1">
<w text="date"/>
</simple>
</w>
</simple>
</or>
</seq>
</loopbody>
</while>
<simple line="331">
<w text="exit"/>
<w text="$exitcode"/>
</simple>
</script>

savelog (9K) Download Attachment

Re: Doubt on variable $<

2009-12-01T05:27:47Z

visco wrote:

> Could anyone tell me what is the purpose of $<
>
> I found it in a Makefile as follows
> $(CXX) $(CXXFLAGS) -c $< -o $@

That's not a bash variable. It's a Makefile variable.

http://www.gnu.org/software/make/manual/make.html#Automatic-Variables

> Also it would be nice if anyone could give a link explaining spl.
> variables used in bash

There's a "Special Parameters" section in the bash man page.

Doubt on variable $<

2009-12-01T05:08:17Z

Could anyone tell me what is the purpose of $<

I found it in a Makefile as follows
$(CXX) $(CXXFLAGS) -c $< -o $@

Also it would be nice if anyone could give a link explaining spl.
variables used in bash

Thanks and regards
visco

Re: operators available in bash versions

2009-12-01T03:12:09Z

On 1 Dec 2009 00:05:09 GMT
Allodoxaphobia Allodoxaphobia <bit-bucket@...> replied:

> You can, doncha know, install ports into $HOME?
> Ergo, you could install bash 3.x and one or more earlier versions
> in $HOME/bin/ and test your scripts to your heart's content.
>
> I found the install 'tricks' via Google, but I don't remember the
> keywords I succeeded with beyond 'freebsd' and 'ports' now...
>
> I successfully installed `alpine` in my FreeBSD shell account
> at a time when the SysAdmin only had `pine` installed.

I have neither the time, inclination to install multiple versions; nor
the morbid fasination to observe what possible system damage may
eventually occur due to that enterprise. If I were writing a script
for eventual mass distribution, I would set up multiple stations, with
various operating systems, and shell versions and do a legitimate test.
I am actually writing for in-house use. I was simply inquiring for
information since I have one of the only two PCs in my organization that
have Bash-4 installed. The others all have various versions of Bash-3.
As each unit is replace, it is updated to the latest OS and software
versions. With the economy as it is, that is not about to happen any
time soon.

--
Gerard
gerard@...

|::::=======
|::::=======
|===========
|===========
|

The opulence of the front office door varies
inversely with the fundamental solvency of the firm.

Re: IFS handling and read

2009-12-01T00:35:20Z

Юрий Пухальский wrote:
> Good day!
>
> Theres is a problem with a following code:
>
> echo a:b|IFS=: read a b; echo $a

this seems work

$ echo "a:b" | { IFS=":" read a b; echo $a; }
a

Re: operators available in bash versions

2009-11-30T16:05:09Z

(Didn't have the OP on the server to followup to. SRI)

> On 30 Nov 2009, at 12:12, Gerard wrote:
>>
>> I apologize for asking what is probably a dumb question, but where can
>> I find a definitive listing of what features are available in each
>> version of Bash.
>>
>> For example, I only have access to Bash-4 on my system. I need to know
>> if " $(< " also works on Bash < 4. I also have a few questions
>> regarding array handling.
>>
>> I am running FreeBSD-7.2 and installed Bash via ports.

You can, doncha know, install ports into $HOME?
Ergo, you could install bash 3.x and one or more earlier versions
in $HOME/bin/ and test your scripts to your heart's content.

I found the install 'tricks' via Google, but I don't remember the
keywords I succeeded with beyond 'freebsd' and 'ports' now...

I successfully installed `alpine` in my FreeBSD shell account
at a time when the SysAdmin only had `pine` installed. WFM

HTH & GL
Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
* Killfiling google & XXXXbanter.com: jonz.net/ng.htm

Re: IFS handling and read

2009-11-30T12:13:00Z

Lhunath (Maarten B.) schrieb:

> My bad. I was under the impression `read` was a Bourne shell-only
thing and not standardized under POSIX.

(not personal for you only, I see that very often)

It would be nice if people actually read POSIX before they talk about it.

Jan

Re: operators available in bash versions

2009-11-30T10:14:03Z

Gerard wrote:

> I apologize for asking what is probably a dumb question, but where can
> I find a definitive listing of what features are available in each
> version of Bash.
>
> For example, I only have access to Bash-4 on my system. I need to know
> if " $(< " also works on Bash < 4. I also have a few questions
> regarding array handling.
>
> I am running FreeBSD-7.2 and installed Bash via ports.
>

could this be a good way to achive this?

$ wget http://ftp.gnu.org/gnu/bash/bash-2.0.tar.gz
--2009-11-30 19:08:52-- http://ftp.gnu.org/gnu/bash/bash-2.0.tar.gz
Resolving ftp.gnu.org... 140.186.70.20
Connecting to ftp.gnu.org|140.186.70.20|:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: 1349450 (1.3M) [application/x-tar]
Saving to: `bash-2.0.tar.gz.1'

100%[======================================>] 1,349,450 285K/s in
5.6s

2009-11-30 19:09:09 (237 KB/s) - `bash-2.0.tar.gz.1' saved [1349450/1349450]

$ tar -zxf bash-2.0.tar.gz bash-2.0/doc/FAQ -O | grep "What.s new in
version"
10) What's new in version 2.0?
10) What's new in version 2.0?

$ wget http://ftp.gnu.org/gnu/bash/bash-3.0.tar.gz

[etc.]

Re: operators available in bash versions

2009-11-30T09:43:44Z

On Mon, Nov 30, 2009 at 12:35:32PM -0500, Mike Frysinger wrote:

> On Monday 30 November 2009 12:12:17 Greg Wooledge wrote:
> > On Mon, Nov 30, 2009 at 11:15:38AM -0500, Mike Frysinger wrote:
> > > On Monday 30 November 2009 06:12:35 Gerard wrote:
> > > > I need to know if " $(< " also works on Bash < 4.
> > >
> > > it's been around for pretty much all time. bash-2 had it for sure, and
> > > that is ancient.
> >
> > It doesn't exist in bash 1.14.7, which is the oldest version I have
> > available. It does exist in 2.04, which is the second oldest I have.
>
> bash-2 was released over a decade ago and for doing any realistic work, that
> is the same as 'all time'. realistically, you're going to run into
> portability problems with the tools run in the script rather than the script
> itself.

Funny thing, how all those scripts I have to write for the machine with
bash 1.14.7 don't count as "realistic"....

Though you're right about the toolset being the main issue. I had
to find a way to express things for the older version of GNU date
(from sh-utils, before coreutils was called coreutils) on that box.
Fortunately, my needs weren't very complex.

Re: operators available in bash versions

2009-11-30T09:35:32Z

On Monday 30 November 2009 12:12:17 Greg Wooledge wrote:
> On Mon, Nov 30, 2009 at 11:15:38AM -0500, Mike Frysinger wrote:
> > On Monday 30 November 2009 06:12:35 Gerard wrote:
> > > I need to know if " $(< " also works on Bash < 4.
> >
> > it's been around for pretty much all time. bash-2 had it for sure, and
> > that is ancient.
>
> It doesn't exist in bash 1.14.7, which is the oldest version I have
> available. It does exist in 2.04, which is the second oldest I have.

bash-2 was released over a decade ago and for doing any realistic work, that
is the same as 'all time'. realistically, you're going to run into
portability problems with the tools run in the script rather than the script
itself.
-mike

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Re: <( error

2009-11-30T09:30:18Z

> Based on your question, I'm guessing you're in bash 3.2 or earlier, where

$ echo $BASH_VERSION
3.2.39(1)-release

$ cat /etc/issue
Debian GNU/Linux 5.0 \n \l

> your "hd <(echo -en \\0{0..3}{0..7}{0..7})" is expanded as if you had typed
> "hd <(echo -en \\0000) <(echo -en \\0001) <(echo -en \\0002) ..." and
> runs into the FD exhaustion issue Chet already described.

thanks for this and your previous post.
bye

Re: IFS handling and read

2009-11-30T09:13:31Z

On Mon, Nov 30, 2009 at 04:21:33PM +0000, Marc Herbert wrote:
> Chris F.A. Johnson a écrit :
> > Why should it be the last element of a pipeline that is executed in
> > the current shell and not the first?
>
> Because that's POSIX' choice?

Because that's what Korn shell does. (But not pdksh, last time I checked.)

Re: operators available in bash versions

2009-11-30T09:12:17Z

On Mon, Nov 30, 2009 at 11:15:38AM -0500, Mike Frysinger wrote:
> On Monday 30 November 2009 06:12:35 Gerard wrote:
> > I need to know if " $(< " also works on Bash < 4.
>
> it's been around for pretty much all time. bash-2 had it for sure, and that
> is ancient.

It doesn't exist in bash 1.14.7, which is the oldest version I have
available. It does exist in 2.04, which is the second oldest I have.

Re: IFS handling and read

2009-11-30T08:35:04Z

pk wrote:

>> Because that's POSIX' choice?
>
> No, POSIX allow either behavior. In fact, it allows any behavior ranging
> from running all parts in their own subshells, to running all parts in the
> current shell.

"...each command of a multi-command pipeline is in a subshell environment;
as an extension, however, any or all commands in a pipeline may be executed
in the current environment. All other commands shall be executed in the
current shell environment."

Re: IFS handling and read

2009-11-30T08:32:30Z

Marc Herbert wrote:

> Chris F.A. Johnson a écrit :
>> Why should it be the last element of a pipeline that is executed in
>> the current shell and not the first?
>
>
> Because that's POSIX' choice?

No, POSIX allow either behavior. In fact, it allows any behavior ranging
from running all parts in their own subshells, to running all parts in the
current shell.

Re: IFS handling and read

2009-11-30T08:21:33Z

Chris F.A. Johnson a écrit :
> Why should it be the last element of a pipeline that is executed in
> the current shell and not the first?

Because that's POSIX' choice?

Because the last element is the last one in the data stream. So it feels
more natural to get everything from the last element rather than side
effects from the first and stdout from the last.

> Suppose that I have a group of commands that sets some variables
> and outputs information to the screen, for example (this is much
> oversimplified):

Thanks for the example. I find this less common than using "read".

Re: operators available in bash versions

2009-11-30T08:15:38Z

On Monday 30 November 2009 06:12:35 Gerard wrote:
> I need to know if " $(< " also works on Bash < 4.

it's been around for pretty much all time. bash-2 had it for sure, and that
is ancient.
-mike

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Re: IFS handling and read

2009-11-30T07:19:37Z

On 30 Nov 2009, at 16:15, Chet Ramey wrote:

>
> Lhunath (Maarten B.) wrote:
>
>> Note that 'read' is a bash feature; not a POSIX shell feature. In that sense, "read" alone is limiting your "portability". So portability in the meaning of POSIX is out of the question.
>
> Pardon me? `read' is a feature of every historical shell and standardized
> by Posix. The bash implementation is a superset of Posix.
>
> Chet
> --
> ``The lyf so short, the craft so long to lerne.'' - Chaucer
> ``Ars longa, vita brevis'' - Hippocrates
> Chet Ramey, ITS, CWRU chet@... http://cnswww.cns.cwru.edu/~chet/

My bad. I was under the impression `read` was a Bourne shell-only thing and not standardized under POSIX.

Re: IFS handling and read

2009-11-30T07:16:21Z

"Chris F.A. Johnson" <chris@...> writes:

> This works with the output of commands, too:
>
> IFS=- read year month day <<.
> $(date +%Y-%m-%d)
> .

The disadvantage is that the command is executed synchronously.

Andreas.

--
Andreas Schwab, schwab@...
GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5
"And now for something completely different."

Re: IFS handling and read

2009-11-30T07:15:58Z

On Mon, 30 Nov 2009, Lhunath (Maarten B.) wrote:

> On 30 Nov 2009, at 15:56, Chris F.A. Johnson wrote:
> >
> > On Mon, 30 Nov 2009, Greg Wooledge wrote:
> >
> >> On Mon, Nov 30, 2009 at 11:46:03AM +0100, Lhunath (Maarten B.) wrote:
> >>> Don't use pipelines to send streams to read. Use file redirection instead:
> >>>
> >>> Instead of ''command | read var''
> >>> Use ''read var < <(command)''
> >>>
> >>> I hardly see a need to change the existing implementation.
> >>
> >> Or for the original problem case, use a here string:
> >>
> >> IFS=: read a b <<< "1:2"
> >>
> >> Between process substitutions (the <(command) thing) and here strings,
> >> you should be able to do all your reads without subshells.
> >
> > Or, to be portable, use a here document:
> >
> > IFS=: read a b <<.
> > 1:2
> > .
> >
> > This works with the output of commands, too:
> >
> > IFS=- read year month day <<.
> > $(date +%Y-%m-%d)
> > .
>
> Note that 'read' is a bash feature; not a POSIX shell feature.

?????

The read command has been around since the early Bourne shells.

> In that sense, "read" alone is limiting your "portability". So
> portability in the meaning of POSIX is out of the question.

> Perhaps you're talking about backward compatibility instead of
> portability, in which case the only compatibility gain you get from
> using the more verbose heredoc over the herestring is compatibiltiy
> with pre-2.05b-alpha1 bash.

> Hardly worth it.
>

--
Chris F.A. Johnson, webmaster <http://woodbine-gerrard.com>
===================================================================
Author:
Shell Scripting Recipes: A Problem-Solution Approach (2005, Apress)
Pro Bash Programming: Scripting the GNU/Linux Shell (2009, Apress)

Re: IFS handling and read

2009-11-30T07:15:06Z

Lhunath (Maarten B.) wrote:

> Note that 'read' is a bash feature; not a POSIX shell feature. In that sense, "read" alone is limiting your "portability". So portability in the meaning of POSIX is out of the question.

Pardon me? `read' is a feature of every historical shell and standardized
by Posix. The bash implementation is a superset of Posix.

Chet
--
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU chet@... http://cnswww.cns.cwru.edu/~chet/

Re: IFS handling and read

2009-11-30T07:07:33Z

On 30 Nov 2009, at 15:56, Chris F.A. Johnson wrote:

>
> On Mon, 30 Nov 2009, Greg Wooledge wrote:
>
>> On Mon, Nov 30, 2009 at 11:46:03AM +0100, Lhunath (Maarten B.) wrote:
>>> Don't use pipelines to send streams to read. Use file redirection instead:
>>>
>>> Instead of ''command | read var''
>>> Use ''read var < <(command)''
>>>
>>> I hardly see a need to change the existing implementation.
>>
>> Or for the original problem case, use a here string:
>>
>> IFS=: read a b <<< "1:2"
>>
>> Between process substitutions (the <(command) thing) and here strings,
>> you should be able to do all your reads without subshells.
>
> Or, to be portable, use a here document:
>
> IFS=: read a b <<.
> 1:2
> .
>
> This works with the output of commands, too:
>
> IFS=- read year month day <<.
> $(date +%Y-%m-%d)
> .

Note that 'read' is a bash feature; not a POSIX shell feature. In that sense, "read" alone is limiting your "portability". So portability in the meaning of POSIX is out of the question.

Perhaps you're talking about backward compatibility instead of portability, in which case the only compatibility gain you get from using the more verbose heredoc over the herestring is compatibiltiy with pre-2.05b-alpha1 bash.

Hardly worth it.

Re: IFS handling and read

2009-11-30T06:56:07Z

On Mon, 30 Nov 2009, Greg Wooledge wrote:

> On Mon, Nov 30, 2009 at 11:46:03AM +0100, Lhunath (Maarten B.) wrote:
> > Don't use pipelines to send streams to read. Use file redirection instead:
> >
> > Instead of ''command | read var''
> > Use ''read var < <(command)''
> >
> > I hardly see a need to change the existing implementation.
>
> Or for the original problem case, use a here string:
>
> IFS=: read a b <<< "1:2"
>
> Between process substitutions (the <(command) thing) and here strings,
> you should be able to do all your reads without subshells.

Or, to be portable, use a here document:

IFS=: read a b <<.
1:2
.

This works with the output of commands, too:

IFS=- read year month day <<.
$(date +%Y-%m-%d)
.

--
Chris F.A. Johnson, webmaster <http://woodbine-gerrard.com>
===================================================================
Author:
Shell Scripting Recipes: A Problem-Solution Approach (2005, Apress)
Pro Bash Programming: Scripting the GNU/Linux Shell (2009, Apress)