Question

I’m having trouble doing something basic with csh. I have a string:

set newCmd = "$expansionCmd –option1 –option2 …"

And I’m creating an array of these strings, which I later want to execute:

set expansionCmdList = ($expansionCmdList[*] "$newCmd")   
#I also tried without quotes, e.g. just $newCmd

Finally I try to iterate over and execute these commands:

foreach exCmd ($expansionCmdList) 
    `exCmd`    #execute it in the shell
end 

However the problem is that the array entries are not the full string, but every part of the string separated by whitespace, i.e. the first entry is just “$expansionCmd”, the next entry would be “—option1” etc.

Apologies in advance for using c shell, my company’s code base is stuck with it.

Answer 1

Any time you are expanding an entire array and want to keep its individual elements’ identities intact, you need the :q (for “quoted”) modifier on the expansion. Otherwise, as soon as you do something like set expansionCmdList=($expansionCmdList[*] "$newCmd"), all previous commands in the list are split out into their component words, each of which is now its own array element. Simple demonstration:

% set a = ( a "b c" d )
% echo $a[2]
b c
% set a = ( $a[*] e )
% echo $a[2]
b

Oops, you’ve messed up the array before you even get to your execution loop. Things go much better with :q:

% set a = ( a "b c" d )
% set a = ( $a:q e )
% echo $a[2]
b c

You need to use the same modifier in the for loop:

foreach exCmd ($expansionCmdList:q) 

Finally, `exCmd` tries to run a command literally named “exCmd”, and then take its output and run that as a command. What you probably want to do is simply execute a command equal to the value of the variable. You will likely run into more whitespace woes here, and you can’t solve them by making each command an array since csh doesn’t support arrays of arrays. Fair warning. But if the commands don’t have any quotation needs, this will work:

  $exCmd