UNIX for Dummies Questions & Answers

For once, not a typow ! The 'b' variable will hold all of the data after the first field (the server name) on each line - e.g. if you used .hosts then it would hold the userid, if you created a specific file then you could have comments or other text after the server name. Without another variable the whole line would be assigned to the 'host' variable.

hope that makes sense

cheers

thestevew,

I created a ksh script that contains the 'while read' loop you described above, and added "echo $host" lines just inside the 'do' and 'done'. I also created a 'listofhostsfile' containing the names of 6 remote boxes.

If I comment out the rcp and rsh commands, the script simply echoes the name of each remote box twice, just as expected. When I uncomment the rcp and rsh lines, the loop only executes for the first remote box. Both 'echo' lines execute. For some reason, the 'while' loop thinks it is finished after the first pass through the rsh/rcp commands.

The same behavior occurs if I 'cat' the hostfile and pipe it into the 'while' loop.
If I do not use the hostfile, but hard-code the box names into a 'for' loop (Ice's script), things work fine.

Any ideas why this would happen? I have verified that the variable 'host' is not used in the script called by rsh. (I'm actually using a variable called 'whost'.) Not sure if this is relevent, but this "wrapper" script is ksh and the script executed by the rsh is "borrowed and modified" csh code that sources its local environment (ie: source /usr/blah/.cshrc).

I appreciate your help!

One thing I've seen upset rsh in the past is terminal i/o - not unreasonable as there is no terminal connected. Are you sure that the script being run on the remote box isn't expecting keyboard input (you can do rsh -n ... to prevent the remote shell from reading from standard input) you might also append to the rsh command ">LogfileName.log 2>&1" (without the quotes) to send any output to a log file (or to /dev/null).
You might also look at adding some logging to the script being run on the remote box - is it failing or doing something unexpected?

hope this helps

As I needed this script to function a couple of days ago, I aborted the "read from external file" concept and hard-coded the box names into a 'for' loop (per Just_Ice's original concept). It worked fine. (Thanks, Ice!)

Every 2-3 months or so I will need to change the list of server names. This would be easy and convenient by using an external file of box names, but honestly, it's just as easy and convenient to edit the script we've been discussing. Either way, it's a quick 'vi' edit on a file.

After my script was working, a coworker supplied a suggestion. I haven't tried it yet, but I thought I'd supply it here for comments:

Instead of hard-coded host names (ex: for host in server1 server2 server3), use an external file and this...

for host in `cat listofhostsfile`

Seems reasonable...

try using a variable name for your list file ... the example below lets you use a different listfile from the command line but uses a default listfile if an argument is not set ... good for testing purposes or for one-offs ... enjoy!

Code:

#! /bin/ksh

listfile=$1
if [ ! -f $listfile ]
then
     listfile=/dir/listfile
fi

for host in `< $listfile`
do
    rcp -p /dir/script $host:/dir/script
    rsh $host "/dir/script"
    rcp -p $host:/dir/script/outfile /outdir/outfile.$host
done

exit 0

BTW, "cat listfile" and "< listfile" does the same thing in sh and ksh (and other shells) but the 2nd form is more efficient since it uses the shell's redirection properties instead of using an external program to read the contents of the file ...