Help checking for mounted share with a bash script

cmfarley19 · 07-03-2008, 10:43 AM

I mount a SMB share at boot-time.

I now have created a script to test to see if the share is mounted.

Code:

#!/bin/bash

SUCCESS=`mount|grep engineer|cut -d '/' -f3`
FAIL=`mount|grep engineers|cut -d '/' -f3`
echo $SUCCESS
echo #FAIL

if [ -n $SUCCESS ]
        then
        echo "Engineer Mounted."
else
        echo "Engineer NOT Mounted."
fi

if [ -n $FAIL ]
        then
        echo "Engineers Mounted."
else
        echo "Engineers NOT Mounted."
fi

This is just a test script.
If I run mount I get:

Code:

root@gcnpd:~/scripts# mount 
/dev/sda1 on / type ext3 (rw,errors=remount-ro)
proc on /proc type proc (rw,noexec,nosuid,nodev)
/sys on /sys type sysfs (rw,noexec,nosuid,nodev)
varrun on /var/run type tmpfs (rw,noexec,nosuid,nodev,mode=0755)
varlock on /var/lock type tmpfs (rw,noexec,nosuid,nodev,mode=1777)
udev on /dev type tmpfs (rw,mode=0755)
devshm on /dev/shm type tmpfs (rw)
devpts on /dev/pts type devpts (rw,gid=5,mode=620)
lrm on /lib/modules/2.6.22-14-generic/volatile type tmpfs (rw)
securityfs on /sys/kernel/security type securityfs (rw)
//gcctfs1/engineer on /media/engineer type smbfs (rw)

The last line is the one of interest.
Here are the results of a run of my script:

Code:

root@gcnpd:~/scripts# ./temp.sh 
gcctfs1

Engineer Mounted.
Engineers Mounted.

Why does the $FAIL case "succeed"?

Any thoughts?

Chris

David the H. · 07-03-2008, 11:53 AM

A good tool for debugging a script is to insert 'set -x' and 'set +x' into your script to turn verbose output on and off (note that it's '-x' for on and '+x' for off), or alternately add -x to the shebang (#!/bin/bash -x) to set it globally. This will output each action as it's completed so you can see what's happening.

When I did this for your script (substituting a text file with your input for 'mount') it showed me this:

Code:

david:~/temp/test$ ./mounttest.sh
++ cat ./testfile.txt
++ grep engineer
++ cut -d / -f3
+ SUCCESS=gcctfs1
++ cat ./testfile.txt
++ grep engineers
++ cut -d / -f3
+ FAIL=
+ echo gcctfs1
gcctfs1
+ echo

+ '[' -n gcctfs1 ']'
+ echo 'Engineer Mounted.'
Engineer Mounted.
+ '[' -n ']'
+ echo 'Engineers Mounted.'
Engineers Mounted.

So for some reason the test function is seeing the '-n $VARIABLE' as a single literal string. You can fix this by putting quotes around the variable names so that they will be seen as unified strings for testing ([ -n "$FAIL" ]). But really you shouldn't even need the '-n' option at all in this case, because if you remove it test will simply check for whether the variable string exists or not. And that should work even if you don't use quotes.

nx5000 · 07-03-2008, 12:12 PM

Ignore post

cmfarley19 · 07-03-2008, 12:14 PM

I am embarrassed that it was that simple.
I forget why I even added the -n in the if statement.

Thank you

David the H. · 07-03-2008, 12:21 PM

Hey, no problem. Sometimes you just need a separate set of eyes to see a problem that you keep overlooking.

0.o · 07-03-2008, 01:11 PM

A much easier way to accomplish the same thing is to use the exit status of the grep command. So, something like this would shorten your script:

Code:

if [[ `mount | grep something` ]]; then
      echo "Mounted"
else
      /usr/bin/mount blah
fi

You could use the ${comamnd} notation too (which is preferred).

nx5000 · 07-03-2008, 01:18 PM

True, that's what I would do. Unless you really need the cutted part.