SED command - MAC address

Question

I use the MAC address of the machine as userid and would like to update a file (display.txt) that will display the userid/expiry. How do I replace the expdate in display.txt with the date in expdate.txt corresponding to the MAC address.

I succeed with the userid part, with:

sed -i "s/user/$(ifconfig eth0 |
                 grep -o -E '([[:xdigit:]]{2}:){5}[[:xdigit:]]{2}')/" \
/user/id/display.txt > /dev/null

---

display.txt:

UserID: user
User expiring on expdate

---

expdate.txt:

user                          = 00:09:34:2C:66:AB
expdate                       = 2017-05-20
user                          = 00:09:34:29:86:6C
expdate                       = 2017-08-23

---

I would like to have:

display.txt:

UserID: 00:09:34:29:86:6C
User expiring on 2017-08-23

Answer 1

I found a one-liner solution using grep and sed:

mac=$(ifconfig eth1 | grep -o -E '([[:xdigit:]]{2}:){5}[[:xdigit:]]{2}'); grep "$mac" expdate.txt -A 1 | sed -r ':a;N;$!ba;s!user.*=.(..\:..\:..\:..\:..\:..).*expdate.*=.(....-..-..)!UserID: \1\nUser expiring on \2!g' > display.txt

and to validate it works with any mac address I tested with:

mac=$(echo "00:09:34:29:86:6C") ; grep "$mac" expdate.txt -A 1 | sed -r ':a;N;$!ba;s!user.*=.(..\:..\:..\:..\:..\:..).*expdate.*=.(....-..-..)!UserID: \1\nUser expiring on \2!g' > display2.txt

I generated the output from scratch, if you need a replacement in an existing file, I suggest to use a templating language like mustache. The Bash version is on GitHub

However because it seems you need to re-use the mac address (for searching first and then for the output) I suggest to make a bash script and it would be more re-usable.

Answer 2

By concatenating sed outputs:

sed -e 's/user/UserID/g' expdate.txt | sed -e 's/ //g' | sed -e 's/=/: /g' | sed -e 's/expdate:/User expiring on/g' > display.txt

(It's pretty sure that this could be done also with only one sed)