Linux operation and maintenance engineers face questions Daquan 04 _ redirection and piping

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1, the standard output standard output after the START command as a previous picture ⼀ commands, called ().
Pipeline |

2, the output of the program and an error message is redirected to file1 file2 command is redirected to the ().
COMMAND> file1 2> file2

3, how to preserve and display the history commands linux command operation is the time?
= HISTTIMEFORMAT "% F.% T"
echo "Export HISTTIMEFORMAT ="% T% F. ">> / etc / Profile

4, there are at / home / stud1 / wang of Contents ⼀ files file, Use () Perform command may be implemented in the background, the command to output the contents of the file
file.copy in files.
A. CAT File> B File.Copy. CAT> File.Copy C. File.Copy CAT File & D. CAT File> File.Copy &
D