How to write dd status/result message to a file? I use this `dd` command for checking disk speed: dd if=/dev/zero of=/path/file bs=1G count=1 oflag=direct which gives back something like this: 1 oflag=direct 1+0 records in 1+0 records out 1073741824 bytes (1,1 GB, 1,0 GiB) copied, 8,52315 s, 126 MB/s Now I would like to pipe this output, not the file `dd` is writing, but to a separate file. I tried adding >> /tmp/foo or | sudo tee /tmp/foo to the `dd` command, but that just creates an empty file.

To be able to insert `dd` in a pipeline before or after another command, its informational messages are written to standard error rather than to standard output.

The OpenBSD manual for `dd` explicitly mentions this (but the Ubuntu manual seems to omit this fact, but mentions it in the more complete `info` page):

> When finished, `dd` displays the number of complete and partial input and output blocks and truncated input records to the **standard error output**.

To redirect standard error from a command, use `2>filename`. To append the standard error stream to an already existing file without truncating it, use `2>>filename`.

For example:


dd if=/dev/zero of=/path/file bs=1G count=1 oflag=direct 2>dd.txt


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Note that you mix appending output in the first of your examples (using `>>`) with truncating output in your second example (using `tee`). To append to a file with `tee`, use `tee -a`.