Process substitution into loop

Tue Jun 14 08:39:51 UTC 2011

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On 14/06/11 04:49, Grail Dane wrote:
> Well, I can confirm that setting the interpreter to /bin/sh does not support process substitution as
> I have run the following script
> under both:
> 
> while read -r DEVICE
> do
>     echo ip link set dev $DEVICE up
> done< <(ip link | awk '/^[0-9]/ && gsub(/:/,""){print $2}')
> 
> Under bash I get:
> 
> ip link set dev lo up
> ip link set dev eth0 up
> ip link set dev sit0 up
> 
> Under sh I get:
> 
> line 6: syntax error near unexpected token `<'
> line 6: `done< <(ip link | awk '/^[0-9]/ && gsub(/:/,""){print $2}')'
> 
> I also have not been able to find a way to successfully implement the Cookbook option to change the
> default shell.
> To this end I mean that if I add the CFLAGS option prior to compiling,
Hi Grail,

You need to set CFLAGS prior to running *configure* (before the compile). So, you will need to do:

export CFLAGS=...
./configure ...
make

Regards,

James.

> the output once running:
> 
> start network-interfaces
> 
> Yields the same type of error as the script above:
> 
> /proc/self/fd/10: line 6: syntax error near unexpected token `<'
> init: network-interfaces main process (27800) terminated with status 2
> start: Job failed to start
> 
> I can confirm that the here document idea does work so I am left with the fact that the CFLAGS option
> was some how no interpreted :(
> 
> Once compiled and installed is there any way to check what shell it thinks is the default?
> 
> Cheers
> grail
> 
> ----------------------------------------------------------------------------------------------------
> Date: Mon, 13 Jun 2011 18:15:20 -0700
> Subject: Re: FW: Process substitution into loop
> From: scott at netsplit.com
> To: grail69 at hotmail.com
> CC: upstart-devel at lists.ubuntu.com
> 
> Note the phrase *startup behaviour* in the paragraph - bash still supports bashisms in its scripts
> when invoked as sh (after all, that's where the entire historical problem with them comes from)
> 
> On Mon, Jun 13, 2011 at 4:56 PM, Grail Dane <grail69 at hotmail.com <mailto:grail69 at hotmail.com>> wrote:
> 
>     Hi James
> 
>     Thanks very much for the reply.  As you can probably guess the typo is in the email but not in
>     the actual script.  I did further testing and as per the bash install instructions:
> 
>     *sh*
> 
>     	
> 
>     A symlink to the *bash* program; when invoked as *sh*, *bash* tries to mimic the startup
>     behavior of historical versions of *sh* as closely as possible, while conforming to the POSIX
>     standard as well
> 
> 
> 
>     This would indicate that it is a bash builtin feature to use only POSIX compliant options.
>     So from the Cookbook you may need to edit the following from the section you pointed me to:
> 
>     If you wish to change this, you can either make /bin/sh a symbolic link to your chosen shell
> 
>     As this does not work as expected in this case and it may be similar for other shells to.
> 
>     I will try the workaround of adding it as the default shell in the build and let you know how it
>     goes :)
> 
>     Cheers
>     grail
> 
>     > Date: Fri, 10 Jun 2011 11:22:12 +0100
>     > From: james.hunt at ubuntu.com <mailto:james.hunt at ubuntu.com>
> 
>     > To: grail69 at hotmail.com <mailto:grail69 at hotmail.com>
>     > CC: upstart-devel at lists.ubuntu.com <mailto:upstart-devel at lists.ubuntu.com>
>     > Subject: Re: Process substitution into loop
>     >
>     > Hi Grail,
>     >
>     > On 10/06/11 05:46, Grail Dane wrote:
>     > >
>     > >
>     > >> Date: Thu, 9 Jun 2011 21:05:45 -0700
>     > >> From: steve.langasek at ubuntu.com <mailto:steve.langasek at ubuntu.com>
>     > >> To: grail69 at hotmail.com <mailto:grail69 at hotmail.com>
>     > >> CC: upstart-devel at lists.ubuntu.com <mailto:upstart-devel at lists.ubuntu.com>
>     > >> Subject: Re: Process substitution into loop
>     > >>
>     > >> On Fri, Jun 10, 2011 at 03:53:15AM +0000, Grail Dane wrote:
>     > >> > Just wondering, as I can't find by googling, if it is at all possible to
>     > >> > do a processsubstitution into a while loop within an upstart script?
>     > >>
>     > >> > Example:
>     > >> > while read -r DEVICE
>     > >> > do
>     > >> > ip link set dev $DEVICE up
>     > >> > done< <(ip link | awk '/^[0-9]/ && !/UP/ && gsub(/:/,""){print $2})
>     > You have an error in your script: it is missing the closing tick (see below).
>     >
>     > >>
>     > >> > When issuing the start command on the script I get:
>     > >> > /proc/self/fd/10: line 6: syntax error near unexpected '<'init:
>     > >> > network-interfaces main process (1367) terminated with status 2start: Job
>     > >> > failed to start Would appreciated if someone would identify if i have done
>     > >> > something wrong or if this not a supported feature?
>     > >>
>     > >> The <() syntax is not part of the POSIX standard, it's a bash extension.
>     > >> Upstart uses /bin/sh to interpret scripts, as is customary; chances are
>     > >> you're running on a system where /bin/sh is not bash, and as a result this
>     > >
>     > > Actually /bin/sh is a symbolic link to bash on my system. Is there anyway to have bash as the
>     > > shell used?
>     >
>     > script
>     > /bin/bash <<EOT
>     > while read -r DEVICE
>     > do
>     > echo "DEBUG: ip link set dev $DEVICE up" > /tmp/grail.log
>     > done < <(ip link | awk '/^[0-9]/ && !/UP/ && gsub(/:/,""){print $2}')
>     > EOT
>     > end script
>     >
>     > Also, just for you :)...
>     >
>     > http://upstart.ubuntu.com/cookbook/#changing-the-default-shell
>     >
>     > Regards,
>     >
>     > James.
>     >
>     > >
>     > >> syntax is not supported.
>     > >>
>     > >> A supported syntax would be:
>     > >>
>     > >> ip link | awk '/^[0-9]/ && !/UP/ && gsub(/:/,""){print $2}' |
>     > >> while read -r DEVICE
>     > >> do
>     > >> ip link set dev $DEVICE up
>     > >> done
>     > >>
>     > >> --
>     > >> Steve Langasek Give me a lever long enough and a Free OS
>     > >> Debian Developer to set it on, and I can move the world.
>     > >> Ubuntu Developer http://www.debian.org/
>     > >> slangasek at ubuntu.com <mailto:slangasek at ubuntu.com> vorlon at debian.org <mailto:vorlon at debian.org>
>     > >
>     >
> 
>     --
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> 
> 

- -- 
Cheers,

James.
- --
James Hunt
____________________________________
Ubuntu Foundations Team, Canonical.
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