I am trying to extract the date and timestamps from my log file string ($Data in the below code) on AIX using a regex and loading it into a text file as below:

Data="Logs/2018-12-03/log.txt:3:2018-12-03 00:00:04,333 452621453 [blah blah blah"
echo "$data" | grep -o -n '[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1]) (2[0-3]|[01][0-9]):[0-5][0-9]' >  timestamps.txt

I get the below error most probably due to the unix version in my host being too old and it doesn't recognize the -o option. Is there any alternative method in which I can get the functionality of -o done?

grep: Not a recognized flag: o
Usage: grep [-r] [-R] [-H] [-L] [-E|-F] [-c|-l|-q] [-insvxbhwyu] [-p[parasep]] -e pattern_list...
    [-f pattern_file...] [file...]
Usage: grep [-r] [-R] [-H] [-L]  [-E|-F] [-c|-l|-q] [-insvxbhwyu] [-p[parasep]] [-e pattern_list...]
    -f pattern_file... [file...]
Usage: grep [-r] [-R] [-H] [-L] [-E|-F] [-c|-l|-q] [-insvxbhwyu] [-p[parasep]] pattern_list [file...]
  • What operating system are you using? – terdon Dec 4 '18 at 9:16
  • The command uname -s gives me 'AIX' – BlueNinja Dec 4 '18 at 9:21
  • 1
    It's not that your Unix is "too old", it's that you are relying on non-standard functionality. – Kusalananda Dec 4 '18 at 9:24
  • Is your Data variable a line from the output of grep? If it is, you can probably do whatever you are doing a fair bit more efficiently by running perl or awk over the original log files. Parsing the output of grep is not an ideal solution. – Kusalananda Dec 4 '18 at 10:41

Note that your regex wouldn't work even if -o was recognized by your grep implementation. You also need -E to enable extended regular expressions. Assuming you have perl, which you probably do, you can try:

$ Data="Logs/2018-12-03/log.txt:3:2018-12-03 00:00:04,333 452621453 [blah blah blah"
$ echo "$Data" | perl -lne '/[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1]) (2[0-3]|[01][0-9]):[0-5][0-9]/ && print "$.:$&"'
1:2018-12-03 00:00

But do you really need to make your regex that complicated? Isn't this enough?

$ echo "$Data" | perl -lne '/\d{4}-\d{2}-\d{2} \d{2}:\d{2}/ && print "$.:$&"'
1:2018-12-03 00:00
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    Note also that the data in the Data variable is a line produced by grep. This makes me think that the user is first running a grep of some kind to get the lines they want, and then iterating in a shell loop over these lines. This is quite an suboptimal approach to log file parsing. – Kusalananda Dec 4 '18 at 10:43

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