As expected: # grep -E 'udisksd\[[[:digit:]]+\]: The string .* ' /var/log/syslog.1 Nov 30 07:16:38 CW8 udisksd[2650]: The string `TSSTcorp CDDVDW SHQeò? ±?¾MUæíE³èBãÄL' is not valid UTF-8. Invalid characters begins at `eò? ±?¾MUæíE³èBãÄL' Nov 30 07:16:38 CW8 udisksd[2650]: The string `TSSTcorp CDDVDW SHQeò? ±?¾MUæíE³èBãÄL' is not valid UTF-8. Invalid characters begins at `eò? ±?¾MUæíE³èBãÄL'
But add the i to the pattern and the behaviour is unexpected: # grep -E 'udisksd\[[[:digit:]]+\]: The string .* i' /var/log/syslog.1 [no output] Apparently grep silently stops processing when it encounters the invalid UTF-8: # grep -E --only-matching 'udisksd\[[[:digit:]]+\]: The string .* ' /var/log/syslog.1 | tail -1 udisksd[2650]: The string `TSSTcorp CDDVDW In case the specific unusual characters are relevant, here they are in hex: # grep -E 'udisksd\[[[:digit:]]+\]: The string .* ' /var/log/syslog.1 | head -1 | cut --delimiter=' ' --fields=10-11 | od -x 0000000 4853 8251 f265 88d0 b120 b8d3 4dbe e655 0000020 45ed e8b3 e342 4cc4 0a27 0000032 When the input has invalid characters so grep cannot process it, a message could be expected perhaps configurable by the -s/--no-messages option because the input is (sort of) unreadable. Version: 2.20 from the Debian Jessie package 2.20-4.1 Charles
