How to achieve redirection in linux

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Linux redirection

First look at > and > >, their two functions are similar, they are output to a file, the only thing is that > will overwrite the original content of the file, and > > is appended after the original content.

Then there is the use of 1 >, 2 >, 1 > >, 2 > >, which is used when the correct output and error output need to be saved separately. For example, when executing a script. Use a simple python script to explain:

The script is as follows:

# coding: utf-8if _ _ name__ = ='_ _ main__': print 'Hello' int (' Hello')

The script first outputs "Hello", which is normal, and then converts "Hello" to int type, where an error is reported. Run directly:

$python test.py > txtTraceback (most recent call last): File "test.py", line 4, in int ('Hello') ValueError: invalid literal for int () with base 10:' Hello'$cat txtHello

You can see that the correct output is saved to the result.txt file, while the error message is output to the screen.

Do the following:

Python test.py 1 > right.txt 2 > wrong.txt$cat right.txtHello$cat wrong.txtTraceback (most recent call last): File "test.py", line 4, in int ('Hello') ValueError: invalid literal for int () with base 10:' Hello'

The correct output is saved to right.txt and the error output is saved to wrong.txt

1 > > and 2 > > and > > are similar, adding new content to the original content.

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