Awk - 仅从文本文件中过滤具有特定格式的日期

Question

I have a .txt file with many lines of text on macOS. I would like to filter only dates and have them saved in order of appearance line by line in a new text file.

I am, however, not interested in all dates, only in those who are complete, looking like 02/03/2019, and those where the number of days is below 13, ie 01...12.

Then, I would like to have those dates removed where the number for the day and month are the same like 01/01/2019 and 02/02/2019 etc.

How can I achieve this with awk or similar software in bash?

Answer 1

If perl is a choice:

perl -ne 'print if m:(\\d\\d)/(\\d\\d)/(\\d\\d\\d\\d): && $1 < 13 && $1 != $2' dates.txt >newdates.txt

this assumes this format /dd/mm/yyyy

Note that I am using a m: : notation instead of the usual / / for regex matching. Thus I do not need to escape the / slashes in the date.

Answer 2

Deleting Dates Inside a Text File

The following command will delete all dates of the form ^✱ aa/bb/cccc where aa = bb < 13. The original file will be copied to yourFile.txt.bak as a backup and the new text with deleted dates will overwrite the old file.

sed -E -i.bak 's:\b(0[0-9]|1[0-2])/\1/[0-9]{4}\b::g' yourFile.txt

If you want to insert something instead of just deleting the dates you can do so by writing the replacement between the two :: . For instance sed … 's:…:deleted date:/g' … will replace each matching date with the text deleted date .

_{✱ Note that it doesn't matter for your criterion whether the date format is dd/mm/yyyy or mm/dd/yyyy since your are only interested in dates where dd and mm are equal.}

Extracting Specific Dates From A Text File

If you do not want to delete, but only extract specific dates as mentioned in your comment, you can use the following command.

grep -Eo '\b([0-9]{2}/){2}[0-9]{4}\b' yourFile.txt | awk -F/ '$1<13 && $1!=$2'

This will extract all dates in dd/mm/yyyy (!) format where mm ≠ dd < 13. The dates are printed in order of appearance on stdin. If you want to save them to a file append > yourOutputFile.txt to the end of the command.