understanding this command

stranger · January 24th, 2012, 11:34 AM

I am having troble understanding this command.
Let me know if the way I understand is correct.
Here's the command :

cat data.txt 2> output.txt 2>&1

My answer: read the error output of the data.txt file and put it in output.txt
and vise versa.

Thanks foe helping.

Troy_lee · September 9th, 2012, 03:45 AM

It is just want to write the stderr and stdout at the same file.The '2' is standard error output,and the '1' is standard output.we should do some work becaus there are two data streams write to the output.txt.
I'm so sorry about my poor english.I hope you could understand what i say.

ciderpunx · October 25th, 2012, 04:53 PM

Quote:

Originally Posted by stranger

I am having troble understanding this command.
Let me know if the way I understand is correct.
Here's the command :

cat data.txt 2> output.txt 2>&1

My answer: read the error output of the data.txt file and put it in output.txt
and vise versa.

Thanks foe helping.

The cat data.txt 2> prints the file data.txt to STDOUT and redirects the output from STDERR into the file output.txt

The 2>&1 redirects STDERR to STDOUT after cat has written its STDERR to output.txt

The result will be an empty output.txt file and data.txt echoed to STDOUT. Like this:

Code:

$ cat data.txt 
data
$ cat data.txt 2> output.txt 2>&1
data
$ cat output.txt 
$