To write the output of a command to a file, there are basically 10 commonly used ways.
Please note that the n.e. in the syntax column means "not existing".
There is a way actually, but it's too complicated to fit into the column. You can find a helpful link in the List section about it.
Overview:
|| visible in terminal || visible in file || existing
Syntax || StdOut | StdErr || StdOut | StdErr || file
==========++==========+==========++==========+==========++===========
> || no | yes || yes | no || overwrite
>> || no | yes || yes | no || append
|| | || | ||
2> || yes | no || no | yes || overwrite
2>> || yes | no || no | yes || append
|| | || | ||
&> || no | no || yes | yes || overwrite
&>> || no | no || yes | yes || append
|| | || | ||
| tee || yes | yes || yes | no || overwrite
| tee -a || yes | yes || yes | no || append
|| | || | ||
n.e. (*) || yes | yes || no | yes || overwrite
n.e. (*) || yes | yes || no | yes || append
|| | || | ||
|& tee || yes | yes || yes | yes || overwrite
|& tee -a || yes | yes || yes | yes || append
List:
command > output.txt
The standard output stream will be redirected to the file only, it will not be visible in the terminal. If the file already exists, it gets overwritten.
command >> output.txt
The standard output stream will be redirected to the file only, it will not be visible in the terminal. If the file already exists, the new data will get appended to the end of the file.
command 2> output.txt
The standard error stream will be redirected to the file only, it will not be visible in the terminal. If the file already exists, it gets overwritten.
command 2>> output.txt
The standard error stream will be redirected to the file only, it will not be visible in the terminal. If the file already exists, the new data will get appended to the end of the file.
command &> output.txt
Both the standard output and standard error stream will be redirected to the file only, nothing will be visible in the terminal. If the file already exists, it gets overwritten.
command &>> output.txt
Both the standard output and standard error stream will be redirected to the file only, nothing will be visible in the terminal. If the file already exists, the new data will get appended to the end of the file..
command | tee output.txt
The standard output stream will be copied to the file, it will still be visible in the terminal. If the file already exists, it gets overwritten.
command | tee -a output.txt
The standard output stream will be copied to the file, it will still be visible in the terminal. If the file already exists, the new data will get appended to the end of the file.
(*)
Bash has no shorthand syntax that allows piping only StdErr to a second command, which would be needed here in combination with tee again to complete the table. If you really need something like that, please look at "How to pipe stderr, and not stdout?" on Stack Overflow for some ways how this can be done e.g. by swapping streams or using process substitution.
command |& tee output.txt
Both the standard output and standard error streams will be copied to the file while still being visible in the terminal. If the file already exists, it gets overwritten.
command |& tee -a output.txt
Both the standard output and standard error streams will be copied to the file while still being visible in the terminal. If the file already exists, the new data will get appended to the end of the file.
來源：https://gist.github.com/raulperula/3b08a44856b61bf000a481e6ed8e50dd
以上命令有個問題
若你的 command "要跑很久很久" 的話
得等你的 command "完全跑完/結束後"，資料才會存到檔案中
