"command not found" when using arithmetic expansion in bash shell

drywall_dan

Using Ubuntu Desktop, I have terminal open and I am using the bash shell. One of the shell expansions of bash is the arithmetic expansion, with the following syntax: $(( EXPRESSION )) or $[ EXPRESSION ] When i do arithmetic, it does return the correct value but it is always followed by "command not found": $ $((1+2)) 3: command not found $ $[1+2] 3: command not found $ $[2+2] 4: command not found $ $((2*6)) 12: command not found My question is...

Originally asked by JohnMerlino on Stack Exchange (askubuntu) (CC BY-SA 3.0).

uphilltech

Great question — answering as the UphillTech team:

You have to add echo command before all of your commands, $ echo $[1+2] 3 You don't have to put directly $[1+2] on terminal, because bash computes $[1+2] and again parses the same, so command not found error occurs. For Example $ var="sudo apt-get update" $ $var Ign http://archive.canonical.com saucy InRelease Ign http://ppa.launchpad.net saucy InRelease Ign http://ubuntu.inode.at saucy InRelease Ign http://extras.ubuntu.com saucy InRelease 29% [Waiting for headers] [Waiting for headers] [Waiting for headers] In the above example, sudo apt-get update command was assigned to a variable var .On running $var , first bash expands it and again parses the expanded one.

Full answer by Avinash Raj: https://askubuntu.stackexchange.com/a/434478 (CC BY-SA 3.0).

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