Indirect parameter substitution in shell script

Question

I\'m having a problem with a shell script (POSIX shell under HP-UX, FWIW). I have a function called print_arg into which I\'m passing the name of a parameter as $1. Given

Answer 1

Even though the answer's already accepted, here's another method for those who need to preserve newlines and special characters like Escape ( \033 ): Storing the variable in base64.

You need: bc, wc, echo, tail, tr, uuencode, uudecode

Example

#!/bin/sh


#====== Definition =======#
varA="a
b
c"
# uuencode the variable
varB="`echo "$varA" | uuencode -m -`"
# Skip the first line of the uuencode output.
varB="`NUM=\`(echo "$varB"|wc -l|tr -d "\n"; echo -1)|bc \`; echo "$varB" | tail -n $NUM)`"


#====== Access =======#

namevar1=varB
namevar2=varA

echo simple eval:
eval "echo \$$namevar2"
echo simple echo: 
echo $varB
echo precise echo: 
echo "$varB"
echo echo of base64
eval "echo \$$namevar1"
echo echo of base64 - with updated newlines
eval "echo \$$namevar1 | tr ' ' '\n'"
echo echo of un-based, using sh instead of eval (but could be made with eval, too)
export $namevar1
sh -c "(echo 'begin-base64 644 -'; echo \$$namevar1 | tr ' ' '\n' )|uudecode"

Result

simple eval:
a b c
simple echo:
YQpiCmMK ====
precise echo:
YQpiCmMK
====
echo of base64
YQpiCmMK ====
echo of base64 - with updated newlines
YQpiCmMK
====
echo of un-based, using sh instead of eval (but could be made with eval, too)
a
b
c

Alternative

You also could use the set command and parse it's output; with that, you don't need to treat the variable in a special way before it's accessed.