Question

Read/Write to file from within linux script

Asked by: zeraxis_ee

I have a linux script, that is scheduled in the crontab to run every minute.

This script, looks at a file (startbrowserext) and read the one line contained in that file.
if it says: "open", then the script opens firefox and then changes the text in the file to "donotopen"

if it says "donotopen" it does nothing.

Basically the text is set to "open" by an external program in which case the script opens firefox.

I have created a script, that reads from the file as below, but not sure how to change the text to "donotopen" once it opened the browser.

The code so far:
#!/bin/sh
 
  fname="startbrowserext"
   
   exec<$fname

   while read line
   do
           
            echo $line;

   
   case "$line" in
   "open")

   
   echo "firefox"
   export DISPLAY=":0.0"
   firefox http://localhost:8080/ZAM
   ;;
   esac
 
   
   done

Thanks

This Question has been solved and asker verified All Experts Exchange premium technology solutions are available to subscription members.

Subscribe now for full access to Experts Exchange and get

Instant Access to this Solution

  • Plus...
  • 30 Day FREE access, no risk, no obligation
  • Collaborate with the world's top tech experts
  • Unlimited access to our exclusive solution database
  • Never be left without tech help again

Subscribe Now

Asked On
2009-01-28 at 04:25:09ID24090399
Topic

SuSE Linux

Participating Experts
1
Points
500
Comments
19

Trusted by hundreds of thousands everyday for fast, accurate and reliable tech support.

  • "The time we save is the biggest benefit of Experts Exchange to Warner Bros. What could take multiple guys 2 hours or more each to find is accessed in around 15 minutes on Experts Exchange." Mike Kapnisakis, Warner Bros.
  • "Our team likes having a resource that is more secure than just using Google and most experts using this service really know their stuff. It's nice to look here first versus using Google." Dayna Sellner, Lockheed Martin
  • "Anytime that I've been stumped with a problem, 9 out of 10 times Experts Exchange has either the accepted solution or an open discussion of the potential solution to the problem." Kenny Red, eBay Inc.

See what Experts Exchange can do for you.

Got a question?

We've got the answer.

Experts Exchange has been collecting answers to technology questions since 1996…3 million and counting! If you have a question, chances are we already have your answer.

Screenshot of Experts Exchange Knowledgebase

Need individual assistance?

Our experts are ready to help.

If you can't find the exact answer you're looking for, ask our exclusive community of 50,000 experts. You’ll get a personalized answer from a trusted professional.

Screenshot of Experts Exchange Knowledgebase

Want to learn from the best?

Read articles from industry experts.

Thousands of free tech tips, tricks, how-to’s and tutorials are available in our peer reviewed articles section. See for yourself how smart our experts are, no login required.

Screenshot of an Article

Working on a long term project?

Store your work and research.

Save solutions to your questions, answers you’ve discovered through searching plus helpful articles in your personal knowledgebase for easy future access.

Screenshot of Experts Exchange Knowledgebase

Access the answers to your technology questions today.

Subscribe Now

30-day free trial. Register in 60 seconds.

What Makes Experts Exchange Unique?

Members of the expert community talk about why the experience at Experts Exchange is different than what you will find anywhere else.

Trusted by the world's most respected brands.

image of each brand's logo

Faithfully serving IT professionals since 1996.

Experts Exchange Logo

Try it out and discover for yourself.

Subscribe Now

30-day free trial. Register in 60 seconds.

Related Solutions

  1. Linux Crontab problem wih Oracle
    I have to update some Oracle tables (residing on Oracle 9i on RedHat Linux 8)with data from a different different Unix Server. This is to be repeated every 10-15 minutes. I have setup crontab for the task. The FTP copy and the Oracle scripts are all in a single shell script, ...
  2. crontab
    hi, can the crontab command be written twice on the same computer? (1st crontab to execute FTP script, wanted to write a crontab to execute the perl program right after FTP script had finish executing) And whether perl program can run crontab? thanks
  3. Linux: Crontab help
    Using crontab how would you ebable a script run once every hour?

Free Tech Articles

  1. WARNING: 5 Reasons why you should NEVER fix a computer for free.
    It is in our nature to love the puzzle. We are obsessed. The lot of us. We love puzzles. We love the challenge. We thrive on finding the answer. We hate disarray. It bothers us deep in our soul. W...
  2. SCCM OSD Basic troubleshooting
    SCCM 2007 OSD is a fantastic way to deploy operating systems, however, like most things SCCM issues can sometimes be difficult to resolve due to the sheer volume of logs to sift through and the dispe...
  3. Migrate Small Business Server 2003 to Exchange 2010 and Windows 2008 R2
    This guide is intended to provide step by step instructions on how to migrate from Small Business Server 2003 to Windows 2008 R2 with Exchange 2010. For this migration to work you will need the fo...
  4. Create a Win7 Gadget
    This article shows you how to create a simple "Gadget" -- a sort of mini-application supported by Windows 7 and Vista. Gadgets can be dropped anywhere on the desktop to provide instant information, ...
  5. Outlook continually prompting for username and password
    There have been a lot of questions recently regarding Outlook prompting for a username and password whilst using Exchange 2007. There are a few reasons why this would happen and I will try to cover t...
  6. Backup Exchange 2010 Information Store using Windows Backup
    There seems to be quite a lot of confusion around the ability to backup Exchange 2010 using the built in Windows Backup feature. This stems from the omission of this feature prior to Exchange 2007 s...

Cloud Class Webinars

  1. Avoiding Bugs in Microsoft Access
    Alison Balter takes and in-depth look at avoiding bugs in Access. In this webinar you will learn about using the immediate window to debug your applications, invoking the debugger, using breakpoints to troubleshoot, stepping through code, setting the next statement to execute, ...
  2. Top 10 Best New Features in Visio 2010
    Scott Helmers gives live demonstrations of the top 10 new features in Visio 2010. This webinar will teach you how to create compelling diagrams by adding shapes to the page with a single click, linking the shapes in a diagram to data in Excel (or SQL Server, or SharePoint), ...
  3. IT Consultant Business Secrets Revealed
    Michael Munger, Experts Exchange tech pro and IT consultant, pulls back the curtain on his very successful businesses and answers question on every IT consultant and business owner should know about. He shares secrets on what he did to solve the 5 most common problems in IT, ...
  4. Disaster Recovery and Business Continuity
    Quest CTO, Mike Billon, gives an overview of the steps involved in building a dunamic disaster recovery plan. Through case studies and an examination of software/hardware tooles for monitoring and testing, you'll gain a better understandin of where you are, where you want ...
  5. Organize Your Visio Diagrams with Containers and Lists
    Scott Helmers uses cross functional flowcharts, wireframe diagrams, data graphic legends and seating charts to teach you: how to ustilize all three new structured diagram components in Visio 2010, the best practices for organizeing shapes in previous version of Visio, how to organize ...
  6. How to Us Objects, Properties, Events and Methods in Microsoft Access
    Alison Dalter gives an in-depbth look at objects, properties, events and methods in Microsoft Access. In this webinar you will learn about using the object browser, referring to objects, working with properties and methods, working with object variables, understanding the ...

Join the Community

Give a Little. Get a Lot.

Join the community of experts here and help other tech pros by answering question in your area of expertise. You can earn FREE access to all Experts Exchange's premium features and resources.

Join the Community

Answers

 

by: CEHJPosted on 2009-01-28 at 04:59:55ID: 23485952

I would try something like the following:

#!/bin/sh
 
FNAME="startbrowserext"
 
if [ ! -f $FNAME ];then
    echo "Flag file $FNAME not present - exiting"
    exit 2
fi
 
DO_OPEN="open"
DO_NOT_OPEN="donotopen"
grep -q $DO_NOT_OPEN $FNAME
if [ $? -eq 0 ];then
        # Browser should not open
        echo "Can't open browser - flagged as open"
        exit 1
else
        # Browser should open, so open it, then prevent opening
        mozilla --display=:0.0 'openURL(http://localhost:8080/ZAM)' && echo $DO_NOT_OPEN >$FNAME
fi
exit $?
                                              
1:
2:
3:
4:
5:
6:
7:
8:
9:
10:
11:
12:
13:
14:
15:
16:
17:
18:
19:
20:
21:

Select allOpen in new window

 

by: CEHJPosted on 2009-01-28 at 05:12:49ID: 23486029

Why are you executing this 'in a loop' (in cron) btw?

 

by: zeraxis_eePosted on 2009-01-28 at 06:22:34ID: 23486688

I tried the code and it opens the browser, but then it closes it down immiately. It also doesn't change open to donotopen.

I tried adding the line echo "donotopen" >$fname  to my bit of code, and that works, the browser stays open
   echo "donotopen" >$fname
   export DISPLAY=":0.0"
   firefox http://localhost:8080/ZAM

but it doesn't always change the open to do not open (sometimes it opens 3 browser instances before it changes it)

The reason why I need to loop it is because the browser is displaying a playlist. The playlist is updated  externally, and when its updated the browser needs to be shut down - while the update happens - and then reopened.  The update can happen any time of the day any number of times, so I sort of have to listen out for it really. Hence the loop.


 

by: CEHJPosted on 2009-01-28 at 06:28:04ID: 23486741

Can you show how you're entering that into cron? You could also try the below instead

mozilla --display=:0.0 'openURL(http://localhost:8080/ZAM)' & && echo $DO_NOT_OPEN >$FNAME

                                              
1:

Select allOpen in new window

 

by: CEHJPosted on 2009-01-28 at 06:29:39ID: 23486757

In your case, it should probably be firefox instead of mozilla

 

by: zeraxis_eePosted on 2009-01-28 at 06:32:21ID: 23486789

yes, I had to change that to firefox --display=:0.0 http://localhost:8080/ZAM && echo $DO_NOT_OPEN >$FNAME

The crontab
* * * * * /home/usera/startbrowser.sh

 

by: CEHJPosted on 2009-01-28 at 06:33:51ID: 23486803

Sorry, typo above, so that should have been

firefox --display=:0.0 'openURL(http://localhost:8080/ZAM)' && echo $DO_NOT_OPEN >$FNAME &

                                              
1:

Select allOpen in new window

 

by: CEHJPosted on 2009-01-28 at 06:43:12ID: 23486905

>>It also doesn't change open to donotopen.

That will only happen on successful browser execution - that's intentional

 

by: CEHJPosted on 2009-01-28 at 06:44:06ID: 23486915

... (since otherwise it would not even attempt it again after failure)

 

by: CEHJPosted on 2009-01-28 at 06:48:59ID: 23486972

There's another complication here too. Can you tell me if (after making the corrections) what happens if you get rid of any existing FF instance before cron opens a new one?

 

by: CEHJPosted on 2009-01-28 at 06:52:50ID: 23487019

>>
and when its updated the browser needs to be shut down - while the update happens - and then reopened.
>>

It would be a whole lot easier just to use the 'ReloadEvery' extension ;-)

 

by: zeraxis_eePosted on 2009-01-28 at 07:48:31ID: 23487668

I changed the code like you suggested... it doesn't like 'openURL(http://localhost:8080/ZAM)' and if I display the command like this, it doesn't open and close the browser anymore:
export DISPLAY=":0.0"
firefox http://localhost:8080/ZAM  && echo $DO_NOT_OPEN >$FNAME &

All instances of firefox are closed, pgrep firefox comes back with nothing.

When the script first runs it opens up the browser, but does not change the open to donotopen
and when I check the processes running, there are 2
e.g.
root     17171  0.0  0.1   2764  1236 ?        S    15:38   0:00 /bin/sh /usr/bi
root     17177  8.5  7.3 293752 57280 ?        SLl  15:38   0:02 /usr/lib/firefo

as the crontab is running this every minute, in a minute another browser opens up and this seem to change the open to donotopen. when I check the processes running, there is no new process but the exact same as before.

Is that paculiar?

What is ReloadEvery extention?

Would that be redirecting the URL somewhere else and then back?
I was thinking about doing that, but not sure how.

 

by: zeraxis_eePosted on 2009-01-28 at 08:11:53ID: 23487920

I see what you mean about the ReloadEvery... but i don't know in advance when exactly the new playlist and playlist files are to be uploaded... and I need to stop or redirect the browser for the duration of the upload

 

by: CEHJPosted on 2009-01-28 at 09:35:52ID: 23488963

>>and I need to stop or redirect the browser for the duration of the upload

Why is that?

 

by: zeraxis_eePosted on 2009-01-29 at 01:45:06ID: 23495564

The browser has a vlc plugin.. for which I need to specify the target playlist (playlist.m3u) file.
This lists all the movies to play, which are sitting in a folder.

When I upload a new playlist and the new movies to play... the browser needs to switch over. If I didn't stop it, it would crash... as it wouldn't be able to find the playlist or the movie files

 

by: zeraxis_eePosted on 2009-01-29 at 06:25:55ID: 31539898

Thanks for all the help

 

by: CEHJPosted on 2009-01-29 at 06:36:33ID: 23497723

:-)

Sorry we couldn't get a cleaner solution, but the following was against us

a. browsers don't permit good control from the command line
b. they're not meant to be repeatedly started and stopped

 

by: zeraxis_eePosted on 2009-01-29 at 06:38:18ID: 23497745

No problem... it was the best solution I could get really... thanks again
Till next time :-)

 

by: CEHJPosted on 2009-01-29 at 06:41:45ID: 23497799

You might try to experiment by killing any existing instances of firefox by pid. That could help smoother startup

20120131-EE-VQP-002

3 Ways to Join

30-Day Free Trial

The Experts

98% positive feedback on 31,087 answers since March 2000. angeliii is a Microsoft Most Valuable Professional for his work with MS SQL Server & Develoment.

He has also proven his knowledge of Visual Basic Programming, PHP Scripting and Oracle Databases.

The Experts

97% positive feedback on 10,752 answers since July 2000. lrmoore has more than 18 years experience in the networking industry.

The six-time Mircosoft MVPs specialties include firewalls, virtual private networking, and network management.

Testimonials

"...and excellent source for support... Kind of like having your very own IT dept." Electriciansnet

Testimonials

"I was apprehensive at signing up at first. However... it has already made my life as an IT administrator much easier." JaCrews

Testimonials

"WOW! You guys have great, active, and knowledgeable people on here." moore50

Business Clients

Business Clients

In the Press

"If you’ve got a question... Experts Exchange can supply an answer.”

In the Press

"...an invaluable aid for both IT professionals and those who require tech support."

In the Press

"where IT professionals provide quick answers on just about any topic"

Business Account Plans

Loading Advertisement...