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(13) Command substitution

`command`

A command (plus optional arguments) enclosed in backticks is executed and the standard output of that command is substituted. If the command produces multiline output, the newlines are retained. If the resultant string is displayed, unquoted, using echo, newlines and multiple spaces will be removed.

$(command)

This syntax is functionally the same as backticks, but commands can be more easily nested.

$(<file)

This is equivalent to `cat file`, but implemented internally for efficiency.

Example: ex3 display, text