Script help (while, pipe and remsh"

[Kellogg Unix Team]

Gurus,

I need some help with the following script. I have a file "a" with the following syntax -
hostA fileA1 fileA2
hostB fileB1 fileB2
hostC fileC1 fileC2
(... and so on)

I want to read this file (one line at a time)and check the existence of files in respective hosts. The script, I am using is -
#!/bin/sh
cat a|while read x y z
do
remsh $a "ll $y $z"
done

The problem is that the script is reading just first line of the file "a" and never goes further. If I replace remsh command with echo (say, echo $x, $y, $z), all line of file "a" are read.

What do I need to make the script work? I am puzzled because echo works but remsh stops after reading first line. (And yes, I do have remsh capability as that user on all hosts listed in file "a")

Thanks in advance
...Manjeet

[harry d brown jr]

WHAT is $a set too??

live free or die
harry

[Hai Nguyen_1 · Accepted solution]

Manjeet,


Replace "remsh $a" with "remsh $a -n".

Hai

[harry d brown jr]

remsh $x -n ll $y $z"


live free or die
harry

[John Poff]

Hi Manjeet,

It looks like you are reading the contents of file 'a' into variables x, y, and z. Shouldn't your 'remsh' line read:

remsh $x "ll $y $z"


JP

[Ray Brewer]

I ran into this a while back and the "-n" is required when running remsh in a loop. The -n option redirects standard input to remsh from /dev/null

Ray

[Ray Brewer]

To expand on my previous reply, here is what the man page on remsh says about the "-n" option and why it is required

By default, remsh reads its standard input and sends it to the remote command because remsh has no way to determine whether the remote command requires input. The -n option redirects standard input to remsh from /dev/null. This is useful when running a shell script containing a remsh command, since otherwise remsh may use input not intended for it. The -n option is also useful when running remsh in the background from a job control shell, /usr/bin/csh or /usr/bin/ksh. Otherwise, remsh stops and waits for input from the terminal keyboard for the remote command. /usr/bin/sh automatically redirects its input from /dev/null when jobs are run in the background.

[Kellogg Unix Team]

Thanks to all for correctly pointing out correct usage of remsh (remsh -n). That did the trick! And thanks for pointing out the typo ! Yes it was "remsh $x "ll $y $z" and not "remsh $a ..." as put in my original post. (I wish there is edit button to edit my first post !!)

Thanks again!

[harry d brown jr]

Ignore that last quote in my past post. cut and paste this:


#!/bin/sh
cat a|while read x y z
do
remsh $x -n "ll $y $z"
done

live free or die
harry