> $ cmd 2>&1 | another-cmd
>> will pipe both stdout and stderr to another-cmd (in bash, that is).
> There is bound to be a magic incantation to pipe stderr only.
for the benefit of newer linux users.
(kenn knows this stuff, but he must have been low on caffeine when he
command 2> file-or-pipe
Mini shell redirection tutorial:
n> means redirect file descriptor n.
fd 1 is normally STDOUT, usually the terminal screen, so command > file
sends output to a file.
fd 2 is normally STDERR, where error messages are sent, usually the terminal
So to send the output of a command to "output-file", and the error messages
to "error-file", you do:
command > output-file 2> error-file
n>&m means: redirect file desc. n to the same place as file desc. m
Eg, 2>&1 means send STDERR to the same place as where we are sending STDOUT.
command > output 2>&1
means "redirect STDOUT to output, redirect STDERR to the same place as
To redirect input, eg keyboard, you use < instead of >. Eg:
command < file1 2> output 1>&2
means: "run command, taking it's input from file, send STDERR to output, and
send STDIN to the same place"
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