table creation in linux

[newbieinlinux]

hi all
i am a linux newbie. please tell me how this code works.

1st statement is clear to me. what does the while IFS statement do.
what is IFS? read -r? un p uid gid j h s;?

Also what does the last statement done</etc/passwd do??

{ printf "%-20s\t%s\t%s\t%s\n" "UserName" "UserID" "GroupID" "Home"
while IFS=: read -r un p uid gid j h s;do
printf "%-20s\t%d\t%d\t%s\n" "$un" "$uid" "$gid" "$h"
done</etc/passwd;}

Please reply .. just now trying to learn linux.. plz

[Cabhan]

I have moved this to a more appropriate forum.

IFS stands for Internal Field Separator. Several things that you do in Bash take in a lot of input, but only give you one "chunk" at a time. The value of IFS determines what separates the "chunks" from one another.

By default, the value of IFS is any whitespace. So a space, a tab, or a newline will separate each chunk.

In the code you are asking about, IFS is being set to ":", which means to use a colon to separate chunks. The read command then reads its input to get seven different variables: $un, $p, $uid, etc.

The last line uses I/O redirection to tell the loop that its standard input is coming from the file /etc/passwd instead of what it was before (by default the terminal, but could be something else based on how the script was executed).

Does this make sense?

[newbieinlinux]

thanks Cabhan.

Now its making sense. Later if i 've any doubts in linux, then i will raise it here. once again thanks..