topic Re: grep in Operating System - HP-UX

grep

khilari — Thu, 23 Mar 2006 09:55:31 GMT

Hi people, okay a command in grep is not working.
i did /etc/passwd | grep
Now, that username was there, but the output that i got was /etc/passwd[14]: mysql:*:102:102::/home/mysql:/sbin/sh: not found. And the list went on like this.
Now, to my understanding, u put in a file name and then concatenate it with grep to find a particular string in that file or what ever is it that u r lookig it in.
So, how come the grep is giving me alist of all the usernames when all i am grepping is a particular and unique username.

Re: grep

Steven E. Protter — Thu, 23 Mar 2006 09:59:39 GMT

shalom,

Try grep username /etc/passwd

You might get better results. You'll certainly get them more efficiently.

SEP

Re: grep

Arunvijai_4 — Thu, 23 Mar 2006 10:06:56 GMT

Hi Khilari,

You should rather use,

# grep -i mysql /etc/passwd

-Arun

Re: grep

Peter Godron — Thu, 23 Mar 2006 10:13:08 GMT

Khilari,
as a second option :
You may have missed out "cat " in front of the /etc/passwd.

Re: grep

Patrick Wallek — Thu, 23 Mar 2006 10:17:17 GMT

If all you did was:

# /etc/passwd | grep

Then no, that will not work. Your example would try to execute the /etc/passwd file, which would not work and would error on each and every line. You got all lines, because 1) they are not valid shell script commands and 2) grep works on 'standard out' file descriptor and everything you saw was going to 'standard error' file descriptor.

You must cat the file and pipe to grep:

# cat /etc/passwd | grep

or you can just use the grep command and specify the file name you are querying at the end of the command, as previous post suggested.

# grep /etc/passwd

Re: grep

Hein van den Heuvel — Thu, 23 Mar 2006 10:18:01 GMT

>> Hi people, okay a command in grep is not working.

Hmm... the unix world as we know it would come to a grinding hold if grep was as badly broken as you suggest.

>> i did /etc/passwd | grep

Ah.... you missed a 'cat ' in front of that, or just use the preferred 'grep ' as already replied.

>> output that i got was /etc/passwd[14]: mysql:*:102:102::/home/mysql:/sbin/sh: not found. And the list went on like this.

Seems to me you are actually EXECUTING passwd as a script and indeed 'mysql' would be a command which is not found.

What is the MODE on /etc/passwd
You should not have an x (execute) bit there.

hth,
Hein.

Re: grep

James R. Ferguson — Thu, 23 Mar 2006 10:22:06 GMT

Hi:

If you are going to 'grep' usernames in '/etc/passwd' I suggest that you do something like:

# grep "^tftp:" /etc/passwd

That is, the caret (^) anchors the search to the beginning of the line. The colon (:) matches the string at the '/etc/passwd's first field end. This will give much more accurate matching and eliminate spurious matching.

Do *not* spawn a new, unnecessary process by doing :

# cat /etc/passwd | grep ...

That is needless and wasteful. 'grep' takes its input from STDIN or the filename supplied as its last argument.

Regards!

...JRF...

Re: grep

khilari — Thu, 23 Mar 2006 12:54:51 GMT

# grep -i mysql /etc/passwd
mysql:*:102:102::/home/mysql:/sbin/sh
# cat /etc/passwd | grep mysql
mysql:*:102:102::/home/mysql:/sbin/sh

Now, y first the grep was before the /etc/passwd and in the other case after it. Yet giving the same output.

Do u huys ever use egrep or fgrep on a regular basis.

Re: grep

James R. Ferguson — Thu, 23 Mar 2006 13:01:32 GMT

Hi (again):

If you use the '-E' and '-F' switches with 'grep' you get the functionalty of 'egrep' and 'fgrep' respectively.

Regards!

...JRF...

Re: grep

Hein van den Heuvel — Thu, 23 Mar 2006 14:05:08 GMT

>> Now, y first the grep was before the /etc/passwd and in the other case after it. Yet giving the same output.

That's very basic Unix shell behaviour.

The syntax for grep and many other commands (zip, head, wc,...) is:

command

If no filename for is provided then in used.

In the second case, you did not give am explicit filespace to grep, so it read STDIN which got it's data piped in from the preceding pipe command.

Clear as mud?

Hein.

Re: grep

Carlos Roberto Schimidt — Thu, 23 Mar 2006 15:02:16 GMT

Hi,

Try use:

# pwget -n username

I think is better

Re: grep

Senthil Prabu.S_1 — Fri, 24 Mar 2006 00:48:15 GMT

Hi,
I think, you missed out "cat". Then it will fail.

Use this;
cat /etc/passwd | grep -i

HTH,
Prabu.S

Re: grep

Muthukumar_5 — Fri, 24 Mar 2006 00:52:35 GMT

# grep -i mysql /etc/passwd
mysql:*:102:102::/home/mysql:/sbin/sh

>>

Some utilities like grep, perl, sed are having capability to open file in the utility itself.

# cat /etc/passwd | grep mysql
mysql:*:102:102::/home/mysql:/sbin/sh

>>

here, grep is getting input from STANDARD INPUT mode using pipe command.

You can use another method as,

grep -i mysql < /etc/passwd

< file will give inputs to some command. < file is more faster than cat |

--
Muthu

Re: grep

Sivakumar TS — Fri, 24 Mar 2006 05:54:26 GMT

Hi,

you pls run either,

#cat /etc/passwd | grep

or

#grep /etc/passwd

It should be OKay,

Regards,

Siva