[ale] help please getting script file to work

Thu Feb 16 09:17:18 EST 2012

+1

I’ve seen more than one user have unexpected results because their /bin/sh was a symbolic link to dash rather than bash.

________________________________
From: ale-bounces at ale.org [mailto:ale-bounces at ale.org] On Behalf Of Jim Kinney
Sent: Wednesday, February 15, 2012 10:49 PM
To: Atlanta Linux Enthusiasts
Subject: Re: [ale] help please getting script file to work

The first line of a file, script, image or other is typically used to indixate what the rest of the file is about or how to use it.
I don't know the history behind the syntax of #!/bin/sh but it won't work without it!
Mike is correct that #!/bin/sh is more generally portable than #!/bin/bash but I often use many bashisms that wont work in csh, ksh, busybox, nash or dash so I got in the habit of being clear on the intended shell to run the script. csh really doesn't play nicely with bash arrays :-)
On Feb 15, 2012 9:28 PM, "Ron Frazier (ALE)" <atllinuxenthinfo at c3energy.com<mailto:atllinuxenthinfo at c3energy.com>> wrote:
Hi Andrew and others,

Thanks for the replies on this thread.  I actually have my script mostly working now in the incarnation directly below when I double click it from the desktop.  I haven't gotten around to trying to auto boot it yet.  I could have posted this question on the NTP questions list at ntp.org<http://ntp.org>, however it was more of a Linux specific thing so I posted it here.  I've been throwing a bunch of other questions at them anyway.

Two things were keeping my script from not working at all, which are now fixed:

The absence of this line: #!/bin/bash, which I'll probably change to #!/bin/sh - as Mike W. suggested.  I have no idea what this does!  Looks like a comment to me.

Also, I had quotes around all the commands, which the system didn't like.

I posted a thread with this subject yesterday: "how I did Ubuntu + NTPD + GPS, but how do I keep it?"  All of my saga is described there.  In answer to your question, my GPS is a GlobalSat BU-353 and I'm running Ubuntu 11.04.

Like I said, the script is essentially working.  It's whole purpose is to stop NTPD, initialize the USB com port for the GPS, then restart NTPD.  I know that the GPS works once that's done.

Right now, I'm having a problem that's driving me insane.  Here's an NTPQ printout before running my script.  Notice that the computer is synchronized closely to the time servers and there is no GPS.  The top server is the current clock.

ron at asus-k52f-1:/etc$ ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*nist1-ny.ustimi .ACTS.           1 u  118  128  377   54.015   -3.923  10.731
-216.119.63.113  .ACTS.           1 u   63  128  377   55.535<tel:128%C2%A0%20377%C2%A0%C2%A0%2055.535>   12.876   3.762
+india.colorado. .ACTS.           1 u   61  128  377   60.914<tel:128%C2%A0%20377%C2%A0%C2%A0%2060.914>   -7.932   2.995
+ping-audit-207- .ACTS.           1 u  126  128  277   84.008   -6.617   5.344

Then, I run the script.  Here is the NTPQ printout shortly after running the script:

ron at asus-k52f-1:/etc$ ntpq -p
     remote           refid      st t when poll reach   delay   offset  jitter
==============================================================================
*GPS_NMEA(5)     .GPS1.           0 l    3    8  377    0.000  595.804  88.950
 nist1-ny.ustimi .ACTS.           1 u    8   64    7   55.065  570.579  52.070
 216.119.63.113  .ACTS.           1 u    6   64    7   55.089  594.824  44.885
 india.colorado. .ACTS.           1 u    7   64    7   60.848  633.795  63.543
 ping-audit-207- .ACTS.           1 u   10   64    7   85.777  576.470  45.730

Now, the GPS has appeared, so I know the USB com port is working.  However, now my clock is ~ 500 ms off from ALL the servers including the GPS.  I have the time coming from the GPS fudged so it closely matches the NIST servers.  So, I don't really think this is related to the GPS, per se, but NTPD is going bonkers or NTPQ is going bonkers.  All I know is I'm going bonkers and I cannot figure out where this instant offset is coming from.

On Windows, using a recent version of the Windows port of NTPD from Dave Hart's website, I can stop the service with it closely synchronized with either the GPS or the internet servers, tinker with the configuration, and restart NTPD and it picks up right where it left off, with almost no additional offset at all.  I MAY have seen it do this once or twice in Windows, but I can't remember for sure.  The restart sequence at the bottom of my script is supposed to clear up the problem, and that seems to work sometimes when I do it manually.

I don't know what's going on here.  Anybody have any clues?  Thanks for all the help.

By the way, I'd also like to know how to make my script print things on the screen as it progresses through.  In DOS, I'd use ECHO, but I don't know the command here.

Sincerely,

Ron

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

Current version of my script file.

#!/bin/bash

# script file to stop ntpd, initialize the usb gps, then restart ntpd
# Ron Frazier - 2012-02-15

# stop ntpd
sudo /etc/init.d/ntp stop

# set up the com port
log_daemon_msg "Setting /dev/ttyUSB0 comm parameters."
sudo stty -F /dev/ttyUSB0 57600 igncr clocal -echo -ixon

# set up link to /dev/gps5
log_daemon_msg "Creating link to /dev/gps5."
sudo ln -T /dev/ttyUSB0 /dev/gps5

# set the clock
sudo ntpdate -b nist1-ny.ustiming.org<http://nist1-ny.ustiming.org>

# start ntpd
sudo /etc/init.d/ntp start

# wait 5 seconds
sleep 5

# ---- cycle ntpd again

# stop and restart ntpd
sudo /etc/init.d/ntp restart

# wait 5 seconds
sleep 5

On 02/15/2012 07:43 PM, Andrew Wade wrote:
Can you tell us the model of the USB GPS device?  I see some other posts about that same command:  stty -F /dev/ttyUSB0 57600 igncr clocal -echo -ixon

I want to understand which commands you are using are working or not (or if you just grabbed them from another source and tried to do the same thing in a different Linux OS with no luck)

Also, what Linux are you using?
On Wed, Feb 15, 2012 at 5:08 PM, Michael H. Warfield <mhw at wittsend.com<mailto:mhw at wittsend.com>> wrote:
On Wed, 2012-02-15 at 14:24 -0500, Jim Kinney wrote:
> add a line at the very beginning of the file as below:

> #!/bin/bash
#!/bin/sh -

If you're not specifically using incompatible bashisms, go with /bin/sh
(which is bash anyways) just as a matter of good practice.  Ends up
doing the same thing, just better practice.

The following dash ('-') is not NEARLY as important on Linux systems as
it is on other flavors of *NIX because SUID scripts are not allowed, but
it's generally a good idea (BCP) to include that '-' and is generally a
standard practice in most "sh/bash/as/ksh" scripts.  There use to be
some old security vulnerabilities on SunOS with SUID scripts where the
'-' was not included, which is where that practice originated.

> better choice to have it start automagically is to write a script modeled
> after the ones in /etc/init.d to set up the gps modem and have that process
> run before the ntpd is started.
Concur.  Create yourself a nice gps-setup script and link it to
99-gps-setup to take care of those things.  Pouring it into rc.local is
an option but not nearly as elegant.

Mike

--

(PS - If you email me and don't get a quick response, you might want to

call on the phone.  I get about 300 emails per day from alternate energy

mailing lists and such.  I don't always see new messages very quickly.)

Ron Frazier

770-205-9422<tel:770-205-9422> (O)   Leave a message.

linuxdude AT c3energy.com<http://c3energy.com>

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