/media/bill/PROJECTS/System_maintenance/Linux/variable read from file as a string.txt
www.BillHowell.ca  18Oct2019 initial


+-----+
variable_eval_test()
{
echo "d_Lucas=  $d_Lucas" 
a='/*_file_insert_path "$d_Lucas""context/waiver, copyright.txt"'
echo "a=  $a"
b=$( echo "$a"  |  sed  's#\/\*_file_insert_path \"\(.*\)\"#\"\1\"#' )
a12=$( eval "echo $b" )
echo "a12=  $a12" 
}
*******************************************






************
18Oct2019  search "Linus bash and how do I evaluate a variable name read in as a string?"

+-----+
https://stackoverflow.com/questions/1921279/how-to-get-a-variable-value-if-variable-name-is-stored-as-string#1921337

You can use ${!a}:

var1="this is the real value"
a="var1"
echo "${!a}" # outputs 'this is the real value'

This is an example of indirect parameter expansion:

    The basic form of parameter expansion is ${parameter}. The value of parameter is substituted.

    If the first character of parameter is an exclamation point (!), it introduces a level of variable indirection. Bash uses the value of the variable formed from the rest of parameter as the name of the variable; this variable is then expanded and that value is used in the rest of the substitution, rather than the value of parameter itself.

edited Mar 22 at 12:41
answered Dec 17 '09 at 12:09
Phil Ross
21.3k99 gold badges6363 silver badges7272 bronze badges

3
	This works for me in OSX bash, but not debian? On debian I get Bad substitution error. – 23inhouse Aug 8 '13 at 3:16
11
	@23inhouse Are you running your script using /bin/sh? If so, try using /bin/bash instead. From Debian Squeeze onwards, /bin/sh was changed to be a symlink for dash instead of bash. dash doesn't support this particular syntax and will output a Bad substitution error. – Phil Ross Aug 8 '13 at 13:56 
8
	Is there a way to make this work for a variable name that belongs to an array? – Loupax Jan 15 '14 at 12:05
	Works on ubuntu with bash – Sergey P. aka azure Sep 25 '14 at 12:13
1
	@DoronShai This is an example of indirect parameter expansion, documented in the Bash Reference Manual at gnu.org/software/bash/manual/html_node/… – Phil Ross May 28 '15 at 11:52

see "/media/bill/PROJECTS/bin/variable eval.sh"


# enddoc