[TriLUG] bash question
jeremyp at pobox.com
Wed Oct 17 22:28:57 EDT 2007
Joseph Mack NA3T wrote:
> On Thu, 18 Oct 2007, Jeremy Portzer wrote:
>> You can also use "eval"
>> CMDA="ls |"
>> CMDB="wc -l"
>> eval "$CMDA$CMDB"
> hmm. I see.
> I had tried
> eval `$CMDA$CMDB`
Well, you're using two different shell constructs together here. The
backtick operator means "run whatever is inside the backticks as a
command and use its output as a command argument." Then, the eval
statement, as discussed, attempts to run its arguments as a shell
command. So, supposing the output of "ls|wc -l" is 34, then what you're
doing in the above is asking bash to run the command "34". This
probably isn't a valid command.
The "eval backick" thing might have a valid use, since obviously the
output of a command *could* be a valid command to use for eval, but I'd
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