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I want to filter standard error for a command that prints status information to standard error. In this case, Borg Backup. Specifically, the default output of borg check includes lines like:

Checking segments ...

sent to standard error. I want to filter those lines out, because they are a nuisance for a cron job. Currently (as of 1.0.2) it is not possible to disable this output via borg configuration.

I used the approach described by Gilles. This works fine for a local Borg repository, for example:

{ borg check '/media/faheem/My Passport/backup-Mail' 2>&1 1>&3 | tr '\r' '\n' | grep -v "^Checking segments" 1>&2; } 3>&1

However, the situation is a little different for a remote repository. The output looks like

Remote: Checking segments 99.3% 
Remote:

How would one modify the reverse grep to get rid of both of these cases?

{ borg check faheem@ramnode:/mnt/backup-Mail 2>&1 1>&3 | tr '\r' '\n' | grep -v ":Checking segments" 1>&2; } 3>&1

works for the first case, but not the second, namely just Remote:. I could use two greps, but I'd prefer one expression.

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To filter out either message in one grep, pull in the -E extended regular expression flag (for the "zero or once" meaning of ? below), and the -v inverse match:

grep -Ev '^Remote:( Checking segments [[:digit:]]{1,3}\.[[:digit:]]%)?$'

which says that the lines should (inverse) match:

  • beginning of line ^
  • the string Remote:
  • the grouped ( ... ) set of characters (with a leading space) Checking segments ..., matched either zero or one times with: ?
  • the [[:digit:]] section says to match between 1 and 3 digit, followed by a period, followed by one digit, and then the % symbol
  • all anchored to the end of the line $

Upon further clarification from the OP, the final grep looks like:

grep -Ev "^Remote:\s*(Checking segments.*)?$"

Which removes any line matching (starting at the beginning ^ of the line), the word "Remote:", then any (or no) amount of whitespace, then either:

  • nothing, or

  • the phrase "Checking segments" itself followed by any (or no) characters .*

... and then the end of the line $

  • Hi Jeff, this gets blocked, which I don't want: echo "Remote: xx" | grep -Ev '^Remote:( Checking segments)?'. And what is the E flag required for? – Faheem Mitha May 1 '16 at 8:24
  • I extended the RE so that the two things it's looking for must match the entire line (anchored in '$'), and so I also had to fill in the percentage RE. – Jeff Schaller May 1 '16 at 11:38
  • It should suffice to just match Checking segments, and allow anything after it. Plus that would be simpler. – Faheem Mitha May 1 '16 at 12:18
  • Replace all that digit stuff with .* then, leaving the $ at the end to anchor – Jeff Schaller May 1 '16 at 14:29
  • So, what would that look like then? grep -Ev '^Remote:( Checking segments :.*)?$'? – Faheem Mitha May 1 '16 at 15:00

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