Shulou(Shulou.com)06/02 Report--

1. Output redirection: standard output: standard error output (2): error information generated during the execution of the command is also output to the terminal standard input: refers to input 2 from the keyboard, standard output redirection (1) function: redirect the information that would have been displayed on the standard output (terminal) to a file if the file does not exist The file is created automatically. Format: > or > > implementation: 1 > and 1 >: empty and rewrite the contents of the target file > >: append after the original content (if the file does not exist Automatically create the file) [root@7 home] # date +% F-%H:%M:%S > a.txt [root@7 home] # cat a.txt 2019-08-14-16:59:04 [root@7 home] # date +% F-%H:%M:%S > > a.txt [root@7 home] # date +% F-%H:%M:%S > > a.txt [root@7 home] # Date +% F-%H:%M:%S > > a.txt [root@7 home] # cat a.txt 2019-08-14-16:59:04 2019-08-14-16:59:28 2019-08-14-16:59:29 2019-08-14-16 purl 593, Error output redirection format: 2 > or 2 > # Standard output > log.txt ls: cannot access / tmpa/: No such file or directory # 2 means to redirect the error message The correct output is still on the terminal [root@7 home] # ls / home/ / tmpa/ 2 > > log.txt / home/: an a.txt log.txt newbook2 example: save the correct information to the file ok.txt file Save the error message to the error.txt file [root@7 home] # ls / home/ / tmpa/ > ok.txt 2 > error.txt [root@7 home] # ls an a.txt error.txt log.txt newbook2 ok.txt [root@7 home] # cat ok.txt / home/: an a.txt error.txt log.txt newbook2 ok.txt [root@7 home] # cat error.txt ls: cannot access / tmpa/: No such file or directory4, Tee command function: output information to the terminal and direct to the file option:-a: the new result is appended to the end of the file (by default, the new content overwrites the old content) [root@7 home] # echo "123" | tee 2.txt [root@7 home] # cat 2.txt 123 [root@7 home] # echo" 321 "| tee 2.txt 321 [root@7 home] # cat 2. Txt example: record the file name under / etc in the file log.txt [root@7 home] # ls / etc > log.txt example: put a. The first three lines of txt are displayed on the desktop Also save [root@7 home] # head-n3 a.txt in the file info.txt | tee info.txt 2019-08-14-16:59:04 2019-08-14-16:59:28 2019-08-14-16:59:29 [root@7 home] # cat info.txt 2019-08-14-16:59:04 2019-08-14-16:59:28 2019-08-14-16:59:29 example: Copy a.txt content to b.txt [root@7 home] # cat a.txt > > b.txt

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