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eval:tldr:8f94a
The given command eval "${echo foo}"
has a syntax error and is not valid. It seems like you are trying to use variable substitution within the eval
command, but the syntax is incorrect.
The correct syntax for variable substitution with eval
would be eval echo foo
, without the double quotes. This would interpret the value of the variable foo
and execute the echo
command.
However, if you meant to provide an example command that showcases variable substitution and command substitution, the correct example would be: eval "$(echo foo)"
.
In this case, the echo foo
command will execute and print the word "foo". The $(...)
syntax allows the result of the command to be substituted. So, the equivalent value is passed to eval
as eval "foo"
. The eval
command will then interpret and execute the command "foo".
Essentially, eval "$(echo foo)"
is used to evaluate and execute the command inside the command substitution.