Now, in terms of why your original code didn't work:
var=$(command_goes_here)
...is the correct syntax. By contrast:
var= $(command_goes_here)
...exports an empty environment variable named var while running command_goes_here, and then while running the output of command_goes_here as its own command.
To show yet another variant,
var = command_goes_here
...runs var as a command, with = as its first argument, and command_goes_here as a subsequent argument. Which is to say, whitespace is important. :)
Don't do it that way at all. Much more efficient is to use built-in shell operations rather than out-of-process tools such as
cut
andrev
.See BashFAQ #100 for a general introduction to best practices for string manipulation in bash, or the bash-hackers page on parameter expansion for a more focused reference on the techniques used here.
Now, in terms of why your original code didn't work:
...is the correct syntax. By contrast:
...exports an empty environment variable named
var
while runningcommand_goes_here
, and then while running the output ofcommand_goes_here
as its own command.To show yet another variant,
...runs
var
as a command, with=
as its first argument, andcommand_goes_here
as a subsequent argument. Which is to say, whitespace is important. :)