How to pipe the output of a command to file on Linux

Question

I am running a task on the CLI, which prompts me for a yes/no.

After selecting a choice, a vast amount of info scrolls on the screen - including several errors. I want to pipe the output to a file so I can see the errors - but a simple '>' is not working since the command expects a keyboar input.

i am running on Ubuntu 9.1

Answer 1

Use 2> rather than just >.

Answer 2

If the program was written by a sane person what you probably want is the stderr not the stdout. You would achieve this by using something like

foo 2> errors.txt

Answer 3

command &> output.txt

You can use &> to redirect both stdout and stderr to a file. This is shorthand for command > output.txt 2&>1 where the 2>&1 means "send stderr to the same place as stdout" (stdout is file descriptor 1, stderr is 2).

For interactive commands I usually don't bother saving to a file if I can use less and read the results right away:

command 2>&1 | less

Answer 4

echo yes | command > output.txt

Depending on how the command reads it's input (some programs discard whatever was on stdin before it displays it's prompt, but most don't), this should work on any sane CLI-environment.