topic Re: Looking for specific user ID's from the passwd file in Operating System - Linux

Looking for specific user ID's from the passwd file

Patrick Ware_1 — Fri, 24 Aug 2007 10:23:29 GMT

Hello,

My issue is that I want to look for specific userids that have their first and last characters are alphabetic followed by four numbers.

I've already got the user ID's out of the passwd file:

more passwd | awk -F ":" '{print $1}' > userids.txt

I just need to know how to just pick the users out of the list that are formated:

aannnn

a=alphabet
n=number

like for example:

ab1234

Thanks in advance!

Re: Looking for specific user ID's from the passwd file

Steven E. Protter — Fri, 24 Aug 2007 10:30:38 GMT

Shalom,

awk has a print format function called printf

Take a look at that and you can do pattern matching.

You may also be able to use grep as a pre or post processor for this script.

SEP

Re: Looking for specific user ID's from the passwd file

Sandman! — Fri, 24 Aug 2007 10:31:08 GMT

# grep '^[a-z]\{2\}[0-9]\{4\}$' infile

Re: Looking for specific user ID's from the passwd file

James R. Ferguson — Fri, 24 Aug 2007 10:31:31 GMT

Hi Patric:

# perl -aF":" -nle 'print $F[0] if $F[0]=~/[A-Za-z]+\d{4}$/' /etc/passwd

That is, split the field of the file on the ":" delimiter. If the first (zero-relative) field consists of one or more letters followed by exactly 4-digits, print the userid.

Regards!

...JRF...

Re: Looking for specific user ID's from the passwd file

Pete Randall — Fri, 24 Aug 2007 10:31:41 GMT

Something like:

grep [a-z][a-z][0-9][0-9][0-9][0-9] userids.txt

should work.

Pete

Re: Looking for specific user ID's from the passwd file

James R. Ferguson — Fri, 24 Aug 2007 10:34:19 GMT

Hi (again) Patrick:

Steven > awk has a print format function called printf. Take a look at that and you can do pattern matching

Hardly, 'printf' does formatted printing not pattern matching.

Regards!

...JRF...

Re: Looking for specific user ID's from the passwd file

Patrick Ware_1 — Fri, 24 Aug 2007 10:41:57 GMT

Pete's anwser was the closest:

I ended up doing this:

more passwd | awk -F ":" '{print $1}' | grep '[A-Za-z][A-Za-z][0-9][0-9][0-9][0-9]'

Re: Looking for specific user ID's from the passwd file

Sandman! — Fri, 24 Aug 2007 10:45:27 GMT

Yet another way to do it using awk(1):

# awk -F: '$1~"[a-z]{2}[0-9]{4}"{print $1}' /etc/passwd

~hope it helps

Re: Looking for specific user ID's from the passwd file

James R. Ferguson — Fri, 24 Aug 2007 10:49:43 GMT

Hi Patrick:

> ended up doing this:

# more passwd | awk -F ":" '{print $1}' | grep '[A-Za-z][A-Za-z][0-9][0-9][0-9][0-9]'

That's a waste of two processes! Let 'awk' open and read the file instead of having 'cat' or 'more' spawn 'awk'. Then, let 'awk' do the matching that it was designed to do, eliminating the 'grep':

# awk -F":" '/[A-Za-z][A-Za-z][0-9][0-9][0-9][0-9]/ {print $1}' /etc/passwd

Regards!

...JRF...

Re: Looking for specific user ID's from the passwd file

Sandman! — Fri, 24 Aug 2007 10:56:05 GMT

Ignore last post and use the one below as it anchors the regular expression:

# awk -F: '$1~"^[a-z]{2}[0-9]{4}$"{print $1}' file

~cheers

Re: Looking for specific user ID's from the passwd file

Patrick Ware_1 — Fri, 24 Aug 2007 11:14:21 GMT

Thanks guys!