Shell Programming and Scripting

> reverse=`tput rev`
> revert=`tput sgr0`

> var="This is some note."
> echo $var
This is some note.

> var2="This is ${reverse}some${revert} note."
> echo $var2
This is some note.

> var3=$(echo $var | sed 's/some/${reverse}some${revert}/g')
> echo $var3
This is ${reverse}some${revert} note.

An alternative to var3 also doesn't work:
> var3=$(echo $var | sed 's/some/`tput rev`some`tput sgr0`/g')
> echo $var3
This is `tput rev`some`tput sgr0` note.

Whats more, I can take the output from my 2nd var3 and do as follows, which works:
> var4="This is `tput rev`some`tput sgr0` note."
> echo $var4
This is some note.

I am working in KSH88. The red text is reflective of the reversed text I see in my terminal window.

Can anyone explain to me why hand creating the text string works but when I create the exact same text with a sed statement the echo does not render the text correctly?

Many Thanks!

Your sed expression is surrounded by single quotes. Nothing expands in single quotes.

Code:

$ VAR="123"

$ echo '${VAR}'
${VAR}

$ echo "${VAR}"
123

$

Excellent! Changed the ' to " on the sed statement and viola. Many thanks!

Although I'm unsure how the command line knows the difference between the text created by me and the sed statement. They are identical at the point the be echo'd aren't they? Is there a hidden character in there?

It's nothing to do with that. It's the difference between things in single quotes and things in double quotes. Things in single quotes never expand -- ever. That's why the shell has them.