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Old 07-26-2016, 03:28 AM   #1
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variables integer vs string

I'm reading the Advanced Bash Scripting Guide (, and I've come across the following:

a=2334                   # Integer.
let "a += 1"
echo "a = $a "           # a = 2335
echo                     # Integer, still.

b=${a/23/BB}             # Substitute "BB" for "23".
                         # This transforms $b into a string.
echo "b = $b"            # b = BB35
declare -i b             # Declaring it an integer doesn't help.
echo "b = $b"            # b = BB35

let "b += 1"             # BB35 + 1
echo "b = $b"            # b = 1
echo                     # Bash sets the "integer value" of a string to 0.
Well, this simply doesn't work: b=${a/23/BB}
At least in Centos 7. If I try it, b has the same value as a. The /23/BB part is simply ignored. I've no idea why.
Old 07-26-2016, 03:37 AM   #2
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Yeah, it was my mistake. I simply wrote '22' instead of '23. So it's just a substitution. So when it finds '23' it replaces it with the second value. But only once.

What if I wanted to change it whenever it finds it?
Old 07-26-2016, 04:31 AM   #3
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You would use double slashes syntax, b=${a//23/BB}
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