Please comment on my bash script

JeremyTheWicked · 2008-10-08 10:07:24

Hi guys.

This is the first bash script I wrote (well - beyond really basic ones).
I run it from ~/.config/openbox/autostart.sh and it is supposed to check whether I'm online and if I am - it starts several internet dependent apps I use. It works great, I would like to have your input though on how I could've done it better/differently.

Here it comes:

#!/bin/bash

STATE_IS="offline"

exec 10</sys/class/net/wlan0/operstate
while read LINE <&10; do
  if [ $LINE = "up" ]; then
    STATE_IS="online"
  fi
done

exec 10</sys/class/net/eth0/operstate
while read LINE <&10; do
  if [ $LINE = "up" ]; then
    STATE_IS="online"
  fi
done

if [ $STATE_IS = "online" ]; then
  thunderbird &
  liferea &
  kadu &
  skype &
  transmission &
  firefox3-bin &
fi

genisis300 · 2008-10-08 10:15:03

Do you really need it to check for the wireless and Ethernet? will that not cuase problems if they are both active.

Good idea thought i might use that my self for a few things.

JeremyTheWicked · 2008-10-08 10:32:20

They are never both active - I only use a cable on rare occasion when there's no wireless network around.

Procyon · 2008-10-08 10:47:28

Interesting use of 'exec n<'. I had to read http://tldp.org/LDP/abs/html/io-redirection.html

Simplest I can think of is this
if [[ $(cat /sys/class/net/{eth0,wlan0}/operstate) =~ up ]]; then
firefox &
fi

JeremyTheWicked · 2008-10-08 11:20:05

what does "=~" do?

Procyon · 2008-10-08 11:29:05

It matches a regex
i.e. you could use this to make sure it's not in a word
if [[ $(cat /sys/class/net/{eth0,wlan0}/operstate) =~ [^a-z]up[^a-z] ]]; then
firefox &
fi

edit: or ... =~ (up|unknown)
Mine seems to be unknown.

Last edited by Procyon (2008-10-08 11:34:05)

JeremyTheWicked · 2008-10-08 11:37:57

Interesting. I don't know too much about bash... Even the double brackets are a little bit of mystery to me. I tried to read about this but never really got to understand the difference between the double brackets and single brackets in an "if" statement.

Procyon · 2008-10-08 12:42:26

Double brackets allow more advanced ==, != and =~
[[ foobar == *oo* ]] && echo yes
while single brackets do not. (they expand the * to filenames)

Some syntax is different, but you get an error message about it anyway. Like you can use && inside the brackets, but not -a.
[ p = p -a a = a ] && echo yes
[[ p = p && a = a ]] && echo yes

JeremyTheWicked · 2008-10-08 12:58:03

Thanks.

I must dive into bash scripting sometime...

fukawi2 · 2008-10-08 21:45:11

Something like this would achieve the same result in a lot less?

#!/bin/bash

STATE_IS="offline"

/bin/egrep -q '^up$' /sys/class/net/wlan0/operstate && STATE_IS='online'
/bin/egrep -q '^up$' /sys/class/net/eth0/operstate && STATE_IS='online'

if [ $STATE_IS = "online" ]; then
  thunderbird &
  liferea &
  kadu &
  skype &
  transmission &
  firefox3-bin &
fi

Arch Linux

#1 2008-10-08 10:07:24

Please comment on my bash script

#2 2008-10-08 10:15:03

Re: Please comment on my bash script

#3 2008-10-08 10:32:20

Re: Please comment on my bash script

#4 2008-10-08 10:47:28

Re: Please comment on my bash script

#5 2008-10-08 11:20:05

Re: Please comment on my bash script

#6 2008-10-08 11:29:05

Re: Please comment on my bash script

#7 2008-10-08 11:37:57

Re: Please comment on my bash script

#8 2008-10-08 12:42:26

Re: Please comment on my bash script

#9 2008-10-08 12:58:03

Re: Please comment on my bash script

#10 2008-10-08 21:45:11

Re: Please comment on my bash script

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