[SOLVED] Why is sed returning more characters than requested

Issue

In a part of my script I am trying to generate a list of the year and month that a file was submitted. Since the file contains the timestamp, I should be able to cut the filenames to the month position, and then do a sort+uniq filtering. However sed is generating an outlier for one of the files.

I am using this command sequence

  ls -1 service*json | sed -e "s|\(.*201...\).*json$|\1|g" | sort |uniq

And this works for most of time except in some cases it outputs the whole timestamp:

$ ls
service-parent-20181119092630.json  service-parent-20181123134132.json  service-parent-20181202124532.json  service-parent-20190121091830.json  service-parent-20190125124209.json
service-parent-20181119101003.json  service-parent-20181126104300.json  service-parent-20181211095939.json  service-parent-20190121092453.json  service-parent-20190128163539.json
service-parent-20181120095850.json  service-parent-20181127083441.json  service-parent-20190107035508.json  service-parent-20190122093608.json
service-parent-20181120104838.json  service-parent-20181129155835.json  service-parent-20190107042234.json  service-parent-20190122115053.json

$ ls -1 service*json | sed -e "s|\(.*201...\).*json$|\1|g" | sort |uniq
service-parent-201811
service-parent-201811201048
service-parent-201812
service-parent-201901

I have also tried this variation but the second output line is still returned:

  ls -1 service*json | sed -e "s|\(.*201.\{3\}\).*json$|\1|g" | sort |uniq

Can somebody explain why service-parent-201811201048 is returned past the requested 3 characters?

Thanks.

Solution

service-parent-201811201048 happens to have 201048 to match 201....

Might try ls -1 service*json | sed -e "s|\(.*-201...\).*json$|\1|g" | sort |uniq to ask for a dash - before 201....

Answered By - Packard CPW