Linux-shell-|, & {}, (), reg-command execution sequence

Linux-shell-|, & amp; & amp ;{}, (), reg-command execution sequence-Linux general technology-Linux programming and kernel information. For details, see the following. (),{}
(Cmd1; cmd2;...; cmdN) # execute a group of commands in a sub-shell
{Cmd1; cmd2;...; cmdN} # execute a group of commands in the Current shell

Regular Expression
^ Match only the beginning of a row
$ Only matches the end of a row
* Only one single character followed by *, matching 0 or more single characters
[] Only matches the characters in. It can be a single character or a character sequence. You can use-to represent the range of character sequences in []. For example, use [1-5] instead of [1 2 3 4 5].
\ Is used only to block the special meaning of a metacharacter. Because sometimes some metacharacters in s h e l have special meanings. \ Can make it meaningless
. Only match any single character
Pattern \ {n \} is only used to match the occurrence times of the previous pattern. N is the number of times
Pattern \ {n, \} m only indicates the same as above, but the minimum number of times is n
Pattern \ {n, m \} only indicates the same as above, but the occurrence frequency of pattern is between n and m.