Looking for regex to extract email addresses from /etc/passwd

Question

Most of my users have email addresses associated with their profile in /etc/passwd. They are always in the 5th field, which I can grab, but they appear at different places within a comma-separated list in the 5th field.

Can somebody give me a regex to grab just the email address (delimeted by commas) from a line in this file? (I will be using grep and sed from a bash script)

Sample lines from file:

user1:x:1147:5005:User One,Department,,,[email protected]:/home/directory:/bin/bash
user2:x:1148:5002:User Two,Department2,[email protected],:/home/directory:/bin/bash

Answer 1

A standard email regular expression should work fine:

http://regexlib.com/DisplayPatterns.aspx

You can also try out the excellent: http://txt2re.com website!

Answer 2

What about:

,([^@]+@[^,:]+)

Where the group contains the email address.

[Updated based upon comment that address doesn't always get terminated by a comma]

Answer 3

BTW The fifth field's known as the GCOS field. Sometimes spelt GECOS.

Answer 4

Search for all email-valid-characters before and after the @ sign. Like:

[-A-z0-9.]+@[-A-z0-9.]+

Greedy matching should pull in everything it can, and it'll stop at the commas or colons.

Check which characters are valid in email addresses, though. I've left some out (like +)

Answer 5

[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*@(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?

should catch most emials

Answer 6

http://www.regular-expressions.info/email.html

Answer 7

Actually, this looks like a perfect job for Awk. Now, like most people I will say "I'm no expert in Awk" before proceeding...

awk -F : '{print $5}' /etc/passwd

would get the 5th field where ':' is the field separator from /etc/passwd - it's probably the 5th field you are wanting.

awk -F , '{print $1}'

would get the 1st field from standard input where ',' was he delimimter so

awk -F : '{print $5}' /etc/passwd | awk -F , '{print $1}'

would get the first comma separated field (the Name field) from the fifth colon separated field (the field with all that kind of cruft in it!) in your /etc/passwd file.

Adjust the print $1 to get the field with your emails in it.

Doubtless there is away to do this without the pipe in Awk. I use Awk for splitting out fields in things and not much else. I find it confusing, and that's from somebody that loves regular expressions...

Answer 8

sed -r -e "s/^.*[,:]([^,:]+@[^,:]+).*$/\1/g" /etc/passwd

Will do the trick

Answer 9

How about the standard RFC 2822:

(?:[a-z0-9!#$%&'*+/=?^_`{|}~-]+(?:\.[a-z0-9!#$%&'*+/=?^_`{|}~-]+)*|"(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21\x23-\x5b\x5d-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])*")@(?:(?:[a-z0-9](?:[a-z0-9-]*[a-z0-9])?\.)+[a-z0-9](?:[a-z0-9-]*[a-z0-9])?|\[(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?|[a-z0-9-]*[a-z0-9]:(?:[\x01-\x08\x0b\x0c\x0e-\x1f\x21-\x5a\x53-\x7f]|\\[\x01-\x09\x0b\x0c\x0e-\x7f])+)\])

Yep. That's it. :)

Answer 10

sed 's/,*:\/.*//;s/^.*://;s/.*,//' /etc/passwd