Group command { command1; command2; [command3; ...] } Must have a
space before/after braces. Last command terminated by a ‘;’.
Subshell (command1; command2; [command3;...])
ls -l > output.txt
echo "Listing of foo.txt" >> output.txt
cat foo.txt >> output.txt
# can be written with a group command
{ ls -l; echo "Listing of foo.txt"; cat foo.txt; } > output.txt
# or as a subshell command
(ls -l; echo "Listing of foo.txt"; cat foo.txt) > output.txt
# groupings really useful for pipelines
{ ls -l; echo "Listing of foo.txt"; cat foo.txt; } | lpr
Note: any changes made in a subshell environment, such as variables are lost when the subshell exits. Therefore most often group commands are preferrable to subshells.