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TVT	07-01-2010 07:41 AM

SH: Recursive Variable Substitution

Hi!

I have the following test code fragment:

Code:

#! /bin/sh



A1='ZZZ'



B='A'

N='1'



if [ "${$B$N}" == 'ZZZ' ]; then echo 'OK'; fi

When I try to run it 'sh' reports the following message^

Code:

test.sh: ${$B...}: Bad substitution

You might understand what I mean with that test code so could you recommend how to achieve the required effect?

Guttorm

07-01-2010 08:49 AM

Hmm. I think you are looking for eval.

Code:

A1="ZZZ"

V1="A"

V2="1"

VARNAME="$V1$V2"

eval VALUE=\$$VARNAME

echo $VALUE

TVT	07-01-2010 09:21 AM

Quote:

Originally Posted by Guttorm (Post 4020537)

Hmm. I think you are looking for eval.

Code:

A1="ZZZ"

V1="A"

V2="1"

VARNAME="$V1$V2"

eval VALUE=\$$VARNAME

echo $VALUE

YES but how to elegantly use your way with 'if' statement?

grail

07-01-2010 09:27 AM

You could possibly go one line less too:

Code:

A1="ZZZ"

V1="A"

V2="1"

eval VARNAME="$V1$V2"

echo ${!VARNAME}

Just an alternative at the end their for indirect

Edit: Use the "if" instead of "echo" line

TVT	07-01-2010 12:57 PM

Quote:

Originally Posted by grail (Post 4020582)

You could possibly go one line less too:

Code:

A1="ZZZ"

V1="A"

V2="1"

eval VARNAME="$V1$V2"

echo ${!VARNAME}

Just an alternative at the end their for indirect

Edit: Use the "if" instead of "echo" line

Doesn't seem to solve the difficulty:

Code:

$ sh -x test1.sh

+ A1=ZZZ

+ V1=A

+ V2=1

+ eval VARNAME=A1

+ VARNAME=A1

test1.sh: ${!V...}: Bad substitution

unSpawn

07-01-2010 01:35 PM

Quote:

Originally Posted by TVT (Post 4020836)

Doesn't seem to solve the difficulty

Is your shell by any chance a "true" Bourne Shell?

TVT	07-01-2010 03:09 PM

Quote:

Originally Posted by unSpawn (Post 4020875)

Is your shell by any chance a "true" Bourne Shell?

No. My shell is just ordinary /bin/sh shell (see message title). This is because some systems do not have bash by default.

tuxdev

07-01-2010 03:30 PM

Quote:

No. My shell is just ordinary /bin/sh shell (see message title). This is because some systems do not have bash by default.

Just because it's /bin/sh doesn't give *any* information on whether it's a actual legacy Bourne shell or a POSIX shell. Please verify that it really is POSIX, not Bourne.

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