Passing parameters to bash script function (or subroutine)

withanh · 02-18-2012, 01:29 PM

I'm kind of stuck on a subroutine that I'm writing in a bash script. I have the script commented with the error lines and the lines that work. Hopefully someone will be able to tell me why the lines with the parameters are not working.

Thanks!

Code:

#!/bin/bash

function waitforvmtools {
# this line works
  /usr/bin/vmware-cmd -H lab-esxi1 -U root -P 'pass!word' '[NFS2] lab-vcenter/lab-vcenter.vmx' gettoolslastactive
# this line should be the same but does not work does not work
  /usr/bin/vmware-cmd -H $1 -U root -P 'pass!word' $2 gettoolslastactive
# but this shows the proper parameters being passed
echo /usr/bin/vmware-cmd -H $1 -U root -P 'pass!word' $2 gettoolslastactive

# this is what I'm ultimately trying to do with it
#  toolstate=`/usr/bin/vmware-cmd -H $1 -U root -P 'pass!word' $2 gettoolslastactive`
#  until [  "$toolstate" = "gettoolslastactive() = 1" ]; do
#    sleep 5
#    toolstate=`/usr/bin/vmware-cmd -H $1 -U root -P 'pass!word' $2 gettoolslastactive`
#    echo $toolstate
#  done
}

waitforvmtools lab-esxi1 "'[NFS2] lab-vcenter/lab-vcenter.vmx'"

PDock · 02-18-2012, 02:09 PM

Have you echoed $2 to see that the space between [NFS2] and lab.... is not messing things up?

withanh · 02-18-2012, 04:22 PM

Quote:

Originally Posted by PDock

Have you echoed $2 to see that the space between [NFS2] and lab.... is not messing things up?

Yes, if I echo the full command line:

Code:

echo /usr/bin/vmware-cmd -H $1 -U root -P 'pass!word' $2 gettoolslastactive

it resolves to:

Code:

/usr/bin/vmware-cmd -H lab-esxi1 -U root -P 'pass!word' '[NFS2] lab-vcenter/lab-vcenter.vmx' gettoolslastactive

The space in there is required, it's how VMware reads the datastore name and file path. If I copy the output from the echo command and paste it to the command prompt, it properly returns the status.

h

David the H. · 02-19-2012, 04:31 AM

When you call the function with this parameter:

Code:

"'[NFS2] lab-vcenter/lab-vcenter.vmx'"

The single quote marks, being escaped by the double-quotes, become literal, and are stored in the variable along with the rest of the string. These are then NOT re-parsed later (generally) as shell syntax. So when you launch the command like this...

Code:

/usr/bin/vmware-cmd -H $1 -U root -P 'pass!word' $2 gettoolslastactive

...the $2 string is passed to the vmware-command as including those literal quote marks.

The echoed command may look the same by eyeball, but to the shell they are completely different, due to the line parsing order. Quotes are processed before variable expansion, so the shell never has a chance to parse the ones stored in the variable.

In addition, since you didn't quote the $2 parameter, the space is processed and the contents are word-split, because word splitting happens after parameter expansion.

So you're actually passing the following two literal strings to vmware-cmd:

Code:

'[NFS2]
lab-vcenter/lab-vcenter.vmx'

It will likely start working if you remove the extra set of quotes from the passed parameter, and double-quote the "$2".

BTW, it's a good idea to train yourself to always quote your variables, parameters, and other expansions, unless and until you actually need word-splitting to occur.

See here for more on how the shell parses arguments:

http://mywiki.wooledge.org/Arguments
http://mywiki.wooledge.org/WordSplitting
http://mywiki.wooledge.org/Quotes

This link goes into more detail about how it's generally not advisable to try storing shell commands/syntax inside variables:

http://mywiki.wooledge.org/BashFAQ/050

withanh · 02-19-2012, 08:53 AM

Thank you for the explanation, that was exactly the issue. I am sure you can tell I'm pretty new to scripting in Linux and the explanation & links you provided will help me greatly.

Thanks again!

Final script version:

Code:

#!/bin/bash

function waitforvmtools {
  toolstate=`/usr/bin/vmware-cmd -H "$1" -U root -P 'pass!word' "$2" gettoolslastactive`
  until [  "$toolstate" = "gettoolslastactive() = 1" ]; do
    sleep 5
    toolstate=`/usr/bin/vmware-cmd -H "$1" -U root -P 'pass!word' "$2" gettoolslastactive`
  done
}

waitforvmtools lab-esxi1 "[NFS2] lab-vcenter/lab-vcenter.vmx"

withanh · 02-19-2012, 08:54 AM

Quote:

Originally Posted by PDock

Have you echoed $2 to see that the space between [NFS2] and lab.... is not messing things up?

Thanks for your reply as well, it appears you were on the right track, I just didn't fully understand how things worked.

h