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I want to replace "Blah: whatever" or "Blah/Whatever" with "Blah--Whatever"

I have this:

NEW=`echo ${OLD} | tr '[:/]' '--'`
echo ${NEW}

I suppose it's taking the 2 dash characters to mean 1 letter replacement for : or /

How do i tell tr to replace : or / with "--"?

using zsh

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up vote 2 down vote accepted

tr only does character-for-character replacements. Try this:

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