On Wed, Feb 9, 2022 at 9:43 PM Bernhard Voelker <m...@bernhard-voelker.de> wrote: > > On 2/9/22 20:14, Nikos Papaspyrou wrote: > > [...] I want the input > > (or the contents of FILE) to go to the standard output untouched. The > > filtered input should only go to FILE1 and FILE2. > > So the original example is possible with the process substitution you already > mentioned, e.g. with tr(1): > > $ dd if=/dev/random of=/dev/null bs=1M count=1000 status=progress \ > |& tee >(tr '\r' '\n' > LOG) > > or with sed(1): > > $ dd if=/dev/random of=/dev/null bs=1M count=1000 status=progress \ > |& tee >( sed 's/\r/\n/g' > LOG)
That's right, I already wrote that. The substitution you're suggesting (both tr and sed) does not achieve the purpose I described, which makes me think you (and Rob) found the description in my first post confusing. Let me explain once again, in a different way this time. Suppose your input is a text with two kinds of "lines": some ending with '\n' and some ending with '\r'. When such a text is printed to standard output, the lines ending with '\r' disappear, because they are overwritten by the lines ending with '\n'. However, if the text is produced and printed slowly, this can be used to implement a progress meter and this is actually useful and appears a lot in practice. Suppose we want to do two things with this input: (1) send it to the standard output, as it is produced, unfiltered because we would like to see the progress meter, and (2) send it to a number of files, filtering out the lines ending with '\r' because we don't care to store the meter's progression in the files. Using tee like this does not achieve the purpose, because it doesn't do the filtering: $ tee FILE1 FILE2 ... This problem can be broken in two parts: finding the right filter and convincing tee to apply the filter as desired. One solution for the first part is this: $ alias remove-cr="sed 's/\r/@REMOVE\n/g' | sed '/@REMOVE$/d'" The second part can indeed be solved with process substitution. If it's just one file, that's easy: $ tee >(remove-cr > FILE) If there are multiple files, it will have to be a little more complicated than: $ tee >(remove-cr > FILE1) >(remove-cr > FILE2) ... because this applies the filter independently N times to the same input, if there are N files. However, it's possible to perform it only once by: $ tee >(remove-cr | tee FILE1 FILE2 ... > /dev/null) So, in conclusion, what the proposed option performs can indeed be achieved by a quite involved construction of pipelines and process substitution, which can all be wrapped up in a script that behaves exactly like my tee --remove-cr. -- Nikolaos Papaspyrou Software Engineer nikol...@google.com Google Germany GmbH Erika-Mann-Strasse 33 80636 Muenchen Geschaeftsfuehrer: Paul Manicle, Halimah DeLaine Prado Registergericht und -nummer: Hamburg, HRB 86891 Sitz der Gesellschaft: Hamburg Diese E-Mail ist vertraulich. Falls Sie diese faelschlicherweise erhalten haben sollten, leiten Sie diese bitte nicht an jemand anderes weiter, loeschen Sie alle Kopien und Anhaenge davon und lassen Sie mich bitte wissen, dass die E-Mail an die falsche Person gesendet wurde. This e-mail is confidential. If you received this communication by mistake, please don't forward it to anyone else, please erase all copies and attachments, and please let me know that it has gone to the wrong person.
