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Old 06-09-2008, 11:03 AM   #1
vikas027
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Question change desired field in passwd or shadow


Hi,

I need to change field as desired in /etc/passwd or /etc/shadow manually separated by delimiter ":"

For eg. I have an entry of /etc/shadow file

vikas:$1$WYD1mVMs$0ntLUvT4UgZ2FDa4V9spw:13991:0:99999:7:::


I need to change 2nd field of it manually which is between 2nd and 3rd colon , ":"

I did some awk and sed work but could suceed.

Pls help.

Thanks in adv.

VIKAS
 
Old 06-09-2008, 11:28 AM   #2
colucix
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In awk you can try something like this
Code:
awk -F: 'BEGIN{OFS=":"}{gsub(/.*/,"newstring",$3)}1' /etc/passwd
or if you want to selectively change the third field - e.g. based on the user name:
Code:
awk -F: 'BEGIN{OFS=":"}/vikas/{gsub(/.*/,"newstring",$3)}1' /etc/passwd
 
Old 06-09-2008, 11:32 AM   #3
vikas027
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Smile

Quote:
Originally Posted by colucix View Post
In awk you can try something like this
Code:
awk -F: 'BEGIN{OFS=":"}{gsub(/.*/,"newstring",$3)}1' /etc/passwd
or if you want to selectively change the third field - e.g. based on the user name:
Code:
awk -F: 'BEGIN{OFS=":"}/vikas/{gsub(/.*/,"newstring",$3)}1' /etc/passwd

Thank you so much, you people rock.
 
Old 06-09-2008, 12:35 PM   #4
vikas027
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Question

Hi Colucix,

Your code is working perfect BUT when I am passing variable in it, the desired position is not changing.

Like in this example, I am looking for user "vikas" in /etc/shadow


Code:
[root@RHEL vikas]# awk -F: 'BEGIN{OFS=":"}/vikas/{gsub(/.*/,"police",$2)}1' /etc/shadow
vikas:police:13991:0:99999:7:::
[root@RHEL vikas]# 

[root@RHEL vikas]# a=$(cat file.txt | head -1 | awk '{print$1}')
[root@RHEL vikas]# echo $a
ZENITH

[root@RHEL vikas]# echo $b
vikas
I have tried passing the value of this variable a in this, but its not giving desired output.
I am looking for user vikas which is in variable b.

Code:
[root@RHEL vikas]# awk -F: 'BEGIN{OFS=":"}/$b/{gsub(/.*/,$a,$2)}1' /etc/shadow | grep vikas
Please help, guess I am making some small mistake.

Thanks in advance.
VIKAS

Last edited by vikas027; 06-09-2008 at 12:47 PM. Reason: I had given a wrong entry
 
Old 06-09-2008, 12:59 PM   #5
colucix
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You cannot pass the value of a shell variable to an awk script in this way. Note that the awk code is enclosed in single quotes, hence $a is passed literally to awk (it is not expanded/evaluated by the shell). To pass an external variable to awk you have to use the -v option like this
Code:
awk -F: -v string=$a 'BEGIN{OFS=":"}/vikas/{gsub(/.*/,string,$2)}1' /etc/shadow
here you assign the value $a to the variable "string" and use this inside the awk code.
 
Old 06-09-2008, 01:03 PM   #6
vikas027
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Hi,

I also meanwhile found other option
Quote:
[root@RHEL vikas]# awk -F: 'BEGIN{OFS=":"}/^'$b'/{gsub(/.*/,'$a',$2)}1' /etc/shadow | grep ^$b: | sed 's/'^$b':/&'$a'/1'
vikas:ZENITH:13991:0:99999:7:::

trying your option too.

Thanks mate, thanks a ton.
 
  


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