Shell Programming and Scripting

Hi All,

Can anyone help me with my SED or should i use AWK?

I would like to replace the first field of shadow file

echo "please enter current username?"
read name
echo "please enter new username?"
read new
TMP=/tmp/test.$$

grep $name | sed 's/$name/$new/g' /etc/shadow > $TMP

My question is:

1. How SED know which field need to replace? as shadow file has 7 fields
X:XX:XXX:XXXX:XXXXX:XXXXXX:XXXXXXX
I would like to replace first field of certain username to new username
2. Can i use AWK instead? But AWK only can only add not replacing

Any advise?

Using awk to replace user(1st field) 'gdm' with 'GD':

Code:

$ awk 'BEGIN {FS=OFS=":"} $1=="gdm" {$1="GD"}{print}' myshadow

//Jadu

Can i do
awk -F: -v user="$name" '$1 == user {print $1="$new"} /etc/shadow

Should be something like:

Code:

awk -v on="$name" -v nn="$new" 'BEGIN{FS=OFS=":"}$1==on{$1=nn}{print}' /etc/shadow > $TMP

Regards

why should you meddle with /etc/shadow directly? if you want to change anything, try using usermod

I agree with ghostdog74. Modifying /etc/shadow, /etc/passwd or /etc/group directly is for the brave. Definitely not something to rehearse on a live system.
Some points:
Log in as root a couple of times and leave one session open for emergency backout.
Be sure to make copies of all three files as a set before editing anything.
Run the checking programs "pwck" and "grpck" first to check that they are sound. Always run "pwck" and "grpck" immediately after any manual edits.
Use the correct utilities (e.g. "usermod", "useradd", "userdel" ... or if you really really do need it "vipw").
Read "man pwconv" because in most unixes this utility is specifically for synchronising /etc/shadow with /etc/passwd.
Be aware that passwords are usually cached for speed. The cache is not refreshed unless you use the correct utilities.

That's true..

But my manager is asking me to create this script because not many people understand unix/linux. He just tries to make everything easier and straight forward without having linux/unix background.