How to repeat a bash shell script until success

How to repeat a bash shell script until success

[Bryan Dunphy]

I have a shell script, originally created for Mac OS X. that waits for an external drive to be mounted (by testing an “ls” of the volume’s root directory for success) then runs an “rsync”
 command. How do I get the script to be run repeatedly until successful exit under Cygwin?

Here is the unmodified Mac OS version of the script:

#!/bin/bash
if ls /Volumes/Shared >/dev/null 2>/dev/null
then
        rsync -avz --compress-level=9 --delete-during --partial --exclude 'cache/' aleph.gutenberg.org::gutenberg /Volumes/Shared/Project-Gutenberg
        exit 0
else
        exit 1
fi


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Re: How to repeat a bash shell script until success

[Brian Inglis]

On 2017-07-12 09:35, Bryan Dunphy wrote:
> I have a shell script, originally created for Mac OS X. that waits for an 
> external drive to be mounted (by testing an “ls” of the volume’s root 
> directory for success) then runs an “rsync” command. How do I get the script
> to be run repeatedly until successful exit under Cygwin?
> 
> Here is the unmodified Mac OS version of the script:
> 
> #!/bin/bash
> if ls /Volumes/Shared >/dev/null 2>/dev/null
> then
>     rsync -avz --compress-level=9 --delete-during --partial --exclude 'cache/' \
>	aleph.gutenberg.org::gutenberg /Volumes/Shared/Project-Gutenberg
>         exit 0
> else
>         exit 1
> fi

Plug your subject line into a web search and read the resulting hits.
Then you don't have to wait 9 hours for hints. ;^>
You could also run "man bash" and RTFM.

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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Re: How to repeat a bash shell script until success

[Gary Johnson]

On 2017-07-12, Bryan Dunphy wrote:
> I have a shell script, originally created for Mac OS X. that waits
> for an external drive to be mounted (by testing an “ls” of the
> volume’s root directory for success) then runs an “rsync” command.
> How do I get the script to be run repeatedly until successful exit
> under Cygwin?
> 
> Here is the unmodified Mac OS version of the script:
> 
> #!/bin/bash
> if ls /Volumes/Shared >/dev/null 2>/dev/null
> then
>         rsync -avz --compress-level=9 --delete-during --partial --exclude 'cache/' aleph.gutenberg.org::gutenberg /Volumes/Shared/Project-Gutenberg
>         exit 0
> else
>         exit 1
> fi

Let the name of your script be "myscript".  The following will run
myscript every two seconds until it succeeds.

    while ! myscript; do sleep 2; done

This is really a bash programming question and is not specific to
Cygwin.

Regards,
Gary


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Re: How to repeat a bash shell script until success

[Gary Johnson]

On 2017-07-12, Bryan Dunphy wrote:
> I have a shell script, originally created for Mac OS X. that waits
> for an external drive to be mounted (by testing an “ls” of the
> volume’s root directory for success) then runs an “rsync” command.
> How do I get the script to be run repeatedly until successful exit
> under Cygwin?
> 
> Here is the unmodified Mac OS version of the script:
> 
> #!/bin/bash
> if ls /Volumes/Shared >/dev/null 2>/dev/null
> then
>         rsync -avz --compress-level=9 --delete-during --partial --exclude 'cache/' aleph.gutenberg.org::gutenberg /Volumes/Shared/Project-Gutenberg
>         exit 0
> else
>         exit 1
> fi

Let the name of your script be "myscript".  The following will run
myscript every two seconds until it succeeds.

    while ! myscript; do sleep 2; done

This is really a bash programming question and is not specific to
Cygwin.

Regards,
Gary


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Re: How to repeat a bash shell script until success

[cyg Simple]

On 7/14/2017 1:27 AM, Gary Johnson wrote:
> On 2017-07-12, Bryan Dunphy wrote:
>> I have a shell script, originally created for Mac OS X. that waits
>> for an external drive to be mounted (by testing an “ls” of the
>> volume’s root directory for success) then runs an “rsync” command.
>> How do I get the script to be run repeatedly until successful exit
>> under Cygwin?
>>
>> Here is the unmodified Mac OS version of the script:
>>
>> #!/bin/bash
>> if ls /Volumes/Shared >/dev/null 2>/dev/null
>> then
>>         rsync -avz --compress-level=9 --delete-during --partial --exclude 'cache/' aleph.gutenberg.org::gutenberg /Volumes/Shared/Project-Gutenberg
>>         exit 0
>> else
>>         exit 1
>> fi
> 
> Let the name of your script be "myscript".  The following will run
> myscript every two seconds until it succeeds.
> 
>     while ! myscript; do sleep 2; done
> 
> This is really a bash programming question and is not specific to
> Cygwin.
> 

In reality the OP script appears to be executed in a crontab system and
executed every X minutes.  So a change to the OP question is needed
which is answered at[1].  Let's remember some people have no real clue
as to what question they should ask and we need to interpret what is
being asked into what should have been asked.  If interpretation isn't
possible then asking for a use case would be warranted.

[1]
https://stackoverflow.com/questions/707184/how-do-you-run-a-crontab-in-cygwin-on-windows

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Re: How to repeat a bash shell script until success

[Kaz Kylheku]

On 12.07.2017 08:35, Bryan Dunphy wrote:
> I have a shell script, originally created for Mac OS X. that waits for
> an external drive to be mounted (by testing an “ls” of the volume’s
> root directory for success) then runs an “rsync”
>  command. How do I get the script to be run repeatedly until
> successful exit under Cygwin?

Multi-line

   while ! program arg1 arg2 ...
   do
     :   # explicit null statement: syntactically mandatory!
   done

one-liner: semicolon between program and "do",
semicolon between : statement and "done":

   while ! program arg1 arg2 ... ; do : ; done

The space between ! and the command is required.

I would throw a sleep in there, not to create a CPU-intensive
busy loop:

   while ! program args ... ; do
     sleep 1
   done


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Re: How to repeat a bash shell script until success

[Brian Inglis]

On 2017-07-14 11:07, Kaz Kylheku wrote:
> On 12.07.2017 08:35, Bryan Dunphy wrote:
>> I have a shell script, originally created for Mac OS X. that waits for
>> an external drive to be mounted (by testing an “ls” of the volume’s
>> root directory for success) then runs an “rsync”
>>  command. How do I get the script to be run repeatedly until
>> successful exit under Cygwin?
> Multi-line
>   while ! program arg1 arg2 ...
>   do
>     :   # explicit null statement: syntactically mandatory!
>   done
> one-liner: semicolon between program and "do",
> semicolon between : statement and "done":
>   while ! program arg1 arg2 ... ; do : ; done
> The space between ! and the command is required.
> I would throw a sleep in there, not to create a CPU-intensive
> busy loop:
>   while ! program args ... ; do
>     sleep 1
>   done

Has everyone forgotten there is also an until loop, supported by at least sh,
dash, bash, [m]ksh:
	until prog ...; do sleep 60; done

-- 
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada

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Re: How to repeat a bash shell script until success

[Sorin Adrian Savu]

On Fri, Jul 14, 2017 at 4:06 PM, cyg Simple <cygsimple@gmail.com> wrote:
>
> On 7/14/2017 1:27 AM, Gary Johnson wrote:
> > On 2017-07-12, Bryan Dunphy wrote:
> >> I have a shell script, originally created for Mac OS X. that waits
> >> for an external drive to be mounted (by testing an “ls” of the
> >> volume’s root directory for success) then runs an “rsync” command.
> >> How do I get the script to be run repeatedly until successful exit
> >> under Cygwin?
> >>
> >> Here is the unmodified Mac OS version of the script:
> >>
> >> #!/bin/bash
> >> if ls /Volumes/Shared >/dev/null 2>/dev/null
> >> then
> >>         rsync -avz --compress-level=9 --delete-during --partial --exclude 'cache/' aleph.gutenberg.org::gutenberg /Volumes/Shared/Project-Gutenberg
> >>         exit 0
> >> else
> >>         exit 1
> >> fi
> >
> > Let the name of your script be "myscript".  The following will run
> > myscript every two seconds until it succeeds.
> >
> >     while ! myscript; do sleep 2; done
> >
> > This is really a bash programming question and is not specific to
> > Cygwin.
> >
>
> In reality the OP script appears to be executed in a crontab system and
> executed every X minutes.  So a change to the OP question is needed
> which is answered at[1].  Let's remember some people have no real clue
> as to what question they should ask and we need to interpret what is
> being asked into what should have been asked.  If interpretation isn't
> possible then asking for a use case would be warranted.
>
> [1]
> https://stackoverflow.com/questions/707184/how-do-you-run-a-crontab-in-cygwin-on-windows


Actually, the correct question would be: how do I run a bash script
when a USB stick is mounted ?

Which is doable via Task Scheduler and a event log trigger. See
https://answers.microsoft.com/en-us/windows/forum/windows_vista-windows_programs/task-scheduler-how-to-automatically-synchronize-my/45a49d83-b1d8-4d37-8896-3d2696cf9795
on how to locate the appropriate event,

As for the script:

- don't use ls for checking file/directory presence use -f/-d (man test)
- you will need to adjust paths (cygwin has windows drives under
/cygdrive (cygpath -h)

On how to run the script from Task Scheduler use an action like this:

C:\Tools\cygwin64\bin\bash.exe -c /cygdrive/c/tools/cygwin64/home/bryan/bkp.sh
(adjust your paths accordingly )
>
>
>
> --
> cyg Simple
>
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Re: How to repeat a bash shell script until success

[cyg Simple]

On 7/15/2017 2:56 AM, Sorin Adrian Savu wrote:
> On Fri, Jul 14, 2017 at 4:06 PM, cyg Simple <cygsimple@gmail.com> wrote:
>>
>> On 7/14/2017 1:27 AM, Gary Johnson wrote:
>>> On 2017-07-12, Bryan Dunphy wrote:
>>>> I have a shell script, originally created for Mac OS X. that waits
>>>> for an external drive to be mounted (by testing an “ls” of the
>>>> volume’s root directory for success) then runs an “rsync” command.
>>>> How do I get the script to be run repeatedly until successful exit
>>>> under Cygwin?
>>>>
>>>> Here is the unmodified Mac OS version of the script:
>>>>
>>>> #!/bin/bash
>>>> if ls /Volumes/Shared >/dev/null 2>/dev/null
>>>> then
>>>>         rsync -avz --compress-level=9 --delete-during --partial --exclude 'cache/' aleph.gutenberg.org::gutenberg /Volumes/Shared/Project-Gutenberg
>>>>         exit 0
>>>> else
>>>>         exit 1
>>>> fi
>>>
>>> Let the name of your script be "myscript".  The following will run
>>> myscript every two seconds until it succeeds.
>>>
>>>     while ! myscript; do sleep 2; done
>>>
>>> This is really a bash programming question and is not specific to
>>> Cygwin.
>>>
>>
>> In reality the OP script appears to be executed in a crontab system and
>> executed every X minutes.  So a change to the OP question is needed
>> which is answered at[1].  Let's remember some people have no real clue
>> as to what question they should ask and we need to interpret what is
>> being asked into what should have been asked.  If interpretation isn't
>> possible then asking for a use case would be warranted.
>>
>> [1]
>> https://stackoverflow.com/questions/707184/how-do-you-run-a-crontab-in-cygwin-on-windows
> 
> 
> Actually, the correct question would be: how do I run a bash script
> when a USB stick is mounted ?
> 
> Which is doable via Task Scheduler and a event log trigger. See
> https://answers.microsoft.com/en-us/windows/forum/windows_vista-windows_programs/task-scheduler-how-to-automatically-synchronize-my/45a49d83-b1d8-4d37-8896-3d2696cf9795
> on how to locate the appropriate event,
> 
> As for the script:
> 
> - don't use ls for checking file/directory presence use -f/-d (man test)
> - you will need to adjust paths (cygwin has windows drives under
> /cygdrive (cygpath -h)
> 

And don't forget the user has the option to change /cygdrive to
something else including / which is my preference.

> On how to run the script from Task Scheduler use an action like this:
> 
> C:\Tools\cygwin64\bin\bash.exe -c /cygdrive/c/tools/cygwin64/home/bryan/bkp.sh
> (adjust your paths accordingly )

Yes, if you don't want to run cygserver, this is another option.  But if
you're moving from a *nix based system then using cron under cygserver
is what you want.

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Re: How to repeat a bash shell script until success

[Ian Lambert via cygwin]

On July 14, 2017 9:06:02 AM EDT, cyg Simple <> wrote:
>On 7/14/2017 1:27 AM, Gary Johnson wrote:
>> On 2017-07-12, Bryan Dunphy wrote:
>>> I have a shell script, originally created for Mac OS X. that waits
>>> for an external drive to be mounted (by .
>> 
>
>In reality the OP script appears to be executed in a crontab system and
>executed every X minutes.  So a change to the OP question is needed
>which is answered at[1].  Let's remember some people have no real clue
>as to what question they should ask and we need to interpret what is
>being asked into what should have been asked.  If interpretation isn't
>possible then asking for a use case would be warranted.
>
>[1]
>https://stackoverflow.com/questions/707184/how-do-you-run-a-crontab-in-cygwin-on-windows

cyg Simple,
Thanks much for this. It seems the link is misleading, because it says cygrunsrv and cron-config must be used to get Cron to work. 

I've been frustrated without admin, being unable to use these. It turns out simply adding 
/usr/sbin/cron to .bashrc will make Cron available. Or, slightly more complicated, 
to avoid "lock" errors:
$HOME/bin/startcron

Containing:

#!/bin/bash
if P=$(pgrep cron)
then
echo "already running, PID is $P"
else
echo "not running, starting now"
/usr/sbin/cron
fi

Thanks!


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Re: How to repeat a bash shell script until success

[Kaz Kylheku]

On 14.07.2017 10:34, Brian Inglis wrote:
> On 2017-07-14 11:07, Kaz Kylheku wrote:
>>   while ! program args ... ; do
>>     sleep 1
>>   done
> 
> Has everyone forgotten there is also an until loop, supported by at 
> least sh,
> dash, bash, [m]ksh:

I've forgotten that at least twice. (I don't remember the exact number 
of times.)


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