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Top Forums Shell Programming and Scripting Bash parameter expansion from a config file Post 302515575 by Corona688 on Wednesday 20th of April 2011 12:19:01 PM
Old 04-20-2011
This doesn't work because bash doesn't substitute twice. If you have a string with "$varname" in it, it won't go back and start over and realize you also wanted $varname to be evaluated, too!

To do that kind of doublethink, you have to stuff it into an eval.

ARGS="$(eval $stringwithvarinit)"

Beware that you can do anything in an eval. Someone could stuff an `rm -rf ~/` in your config file and it could run it.
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eval(1T)						       Tcl Built-In Commands							  eval(1T)

__________________________________________________________________________________________________________________________________________________

NAME
eval - Evaluate a Tcl script SYNOPSIS
eval arg ?arg ...? _________________________________________________________________ DESCRIPTION
Eval takes one or more arguments, which together comprise a Tcl script containing one or more commands. Eval concatenates all its argu- ments in the same fashion as the concat command, passes the concatenated string to the Tcl interpreter recursively, and returns the result of that evaluation (or any error generated by it). Note that the list command quotes sequences of words in such a way that they are not further expanded by the eval command. EXAMPLE
This procedure acts in a way that is analogous to the lappend command, except it inserts the argument values at the start of the list in the variable: proc lprepend {varName args} { upvar 1 $varName var # Ensure that the variable exists and contains a list lappend var # Now we insert all the arguments in one go set var [eval [list linsert $var 0] $args] } KEYWORDS
concatenate, evaluate, script SEE ALSO
catch(1T), concat(1T), error(1T), list(1T), subst(1T), tclvars(1T) ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +--------------------+-----------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +--------------------+-----------------+ |Availability | SUNWTcl | +--------------------+-----------------+ |Interface Stability | Uncommitted | +--------------------+-----------------+ NOTES
Source for Tcl is available on http://opensolaris.org. Tcl eval(1T)
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