linux simple operation

On the shell:
0 means standard input
1 means standard output
2 means standard error output
2>&1 means: redirect standard error output to standard output.

> means output redirection

|: is a pipe, example:
cmd1 | cmd2 means: The standard output of the command cmd1 is the standard input of cmd2.

Explain the third command line in detail, (ls you no;ls yes) 2>&1|egrep \* >file:
2>&1 means: redirect the standard error output to Standard output.
| means: pipe;
egrep \*: search all strings.
>file: import standard output into file file (if file exists, empty file, if not, create.);