Braces

Subshell

This creates subshell, so variables and state is not persisted.

(cd Documents && ls)

Evaluate

Here getting the result of a command and evaluating it immediately. One case is where you have a command that produces line of environment variables and you want those to be set in the outer scope.

$(set-creds)

Here getting the result of a command and using it in the outer command.

ls -l $(which deno)

rm $(which deno)

Output Grouping

Usig curly braces to group output. I have rarely seen this.

{ EXPRESSION }

{ EXPRESSION } > PATH

Note that you need spaces because the braces are reserved words.

It is recommended to use a semicolon between commands if you don’t want the expression to stop.

{ COMMAND ; COMMAND ; COMMAND }

Example 1

From All about {Curly Braces} in Bash article.

Here only the output ls as the last command gets written.

echo "I found all these PNGs:"; find . -iname "*.png"; echo "Within this bunch of files:"; ls > PNGs.txt

Here it all gets written.

{ echo "I found all these PNGs:"; find . -iname "*.png"; echo "Within this bunch of files:"; ls; } > PNGs.txt

Example 2

My own testing.

$ wc -l dump.json
    9444 dump.json

$ { wc -l dump.json ; wc -c dump.json }
    9444 dump.json
 3777324 dump.json

I see its use in writing output of multiple commands to a file without having to capture as a variable.

$ { wc -l dump.json ; wc -c dump.json } > test.txt
$ cat test.txt
    9444 dump.json
 3777324 dump.json