CODEWITHSUNDEEP
ksh
mtruesdell
mtruesdell

Reputation: 3747

How can you get a variable's value given its name in korn shell?

Is there a way in ksh to get a variable's value when you have been given the name of the variable?

For example:

#!/usr/bin/ksh
var_name=$1  #pretend here that the user passed the string "PATH"
echo ${$var_name}  #echo value of $PATH -- what do I do here?

Upvotes: 2

Views: 10288

Answers (4)

shortbaldman
shortbaldman

Reputation: 174

var_name=$1  #pretend here that the user passed the string "PATH"
printenv    $var_name

Upvotes: 1

Brett Allen
Brett Allen

Reputation: 1

For one step above your answer (I spent a lot of time trying to find both these answers). The below will allow you to export a dynamic variable and then recall it dynamically:

echo -n "Please provide short name for path:"
read PATH_SHORTCUT
echo -n "Please provide path:"
read PATH
eval export \${PATH_SHORTCUT}_PATH="${PATH}"
eval echo Path shortcut: ${PATH_SHORTCUT} set to \$"${PATH_SHORTCUT}_PATH".

Upvotes: 0

Henk Langeveld
Henk Langeveld

Reputation: 8456

printenv is not a ksh builtin and may not always be present. For older ksh versions, prior to ksh93, the eval 'expression' method works best.

A powerful method in ksh93 is to use indirection variables with 'nameref' or 'typeset -n'.

Define and verify a nameref variable that refers to $PATH:

$ nameref indirect=PATH
$ print $indirect
/usr/bin:/usr/sbin

See how the nameref variable changes when we change PATH:

$ PATH=/usr/bin:/usr/sbin:/usr/local/bin
$ print $indirect
/usr/bin:/usr/sbin:/usr/local/bin

Show ksh version and the alias for nameref:

$ type nameref
nameref is an alias for 'typeset -n'
$ echo ${.sh.version}
Version JM 93t+ 2010-02-02

Upvotes: 2

Kevin Beck
Kevin Beck

Reputation: 2390

eval `echo '$'$var_name`

echo concatenates a '$' to the variable name inside $var_name, eval evaluates it to show the value.

EDIT: The above isn't quite right. The correct answer is with no backticks.

eval echo '$'$var_name

Upvotes: 9

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