Re: bash error handling help

["Chris F.A. Johnson" <cfajohnson@gmail.com>]

On 2005-06-04, theal wrote:
> I am have a script that uses a for loop to copy files to about 100 servers.
> I know how to get it to exit the entire script on an error, but I only want
> to stop what it is doing for the current $i and move to the next. here is
> the basics of the script. there may be some syntax errors in this script as
> I have edited it for public viewing.
>
> #!/bin/bash
>
> hostlist=`less /usr/local/src/client_hosts.txt|grep -v "#"|cut -d "," -f1`

   Why are you using less? That's for interactive use; it's even worse
   than cat. Just use the filename as an argument to grep:

hostlist=`grep -v "#" /usr/local/src/client_hosts.txt | cut -d "," -f1`

   Or:

hostlist=`awk '!/#/ {print $1}' /usr/local/src/client_hosts.txt`

> if [ ! -f /usr/local/bin/myfile_client.sh ] ; then
>     echo "/usr/local/bin/myfile_client.sh does not exist"
>     exit 1
> fi
>
> function log()
> {
>     echo [`date "+%Y-%m-%d %H:%M"`] $1
>     echo [`date "+%Y-%m-%d %H:%M"`] $1 >> /usr/local/bin/myfile.log
>     echo [`date "+%Y-%m-%d %H:%M"`] $1 >> /tmp/myfile.log
> }
>
> function run()
> {
>     CMD=$1
>
>     # Don't abort on errors
>     set +e
>     # Capture STDERR to ERR
>     ERR=$($CMD 2>&1)
>     # Capture return value from command
>     RETVAL=$?
>     # re-enable abort-on-err
>     # set -e
>
>     if [ "$ERR" ] ; then
>         log "Error processing: $ERR"
>     fi
>
>     return $RETVAL
> }

    Why did you include this function? You don't use it in your
    example, but you use cleanup, and didn't include that.

> function errhandler()
> {
>     log "Aborting abnormally..."
>     cleanup
> }
>
> trap errhandler ERR

   Why?

   Why not just check that each command completes successfully?

   If you don't want to exit on all errors, why install a trap that
   does?

> for i in $hostlist
>     do
>         echo "determine if temp exits"
>         if [ -f /tmp/temp ] ; then
>             rm /tmp/temp
>         elif [ -d /tmp/temp ] ; then
>             rm -rf /tmp/temp
>         fi
>
>         echo "Creating client /tmp/temp directory"
>         log "Creating client /tmp/temp directory"
>         ssh -i ~/.ssh/$i me@$i "mkdir -p /tmp/temp/"
>
>         echo "Transfering files to $i:/tmp/temp"
>         log "Transfering files to $i:/tmp/temp"
>         scp -i ~/.ssh/$i /usr/local/bin/myfile.sh me@$i:/tmp/temp
>
>         echo "Executing myfile.sh"
>         log "Executing myfile.sh"
>         ssh -i ~/.ssh/$i me@$i "/tmp/temp/myfile.sh"
>
>         echo "Removing client /tmp/temp"
>         log "Removing client /tmp/temp"
>         ssh -i ~/.ssh/$i me@$i "rm -rf /tmp/temp"
>
>         echo "Finished $i myfile.sh "
>         log "Finished $i myfile.sh "
>         echo " "
> done


-- 
    Chris F.A. Johnson                     <http://cfaj.freeshell.org>
    ==================================================================
    Shell Scripting Recipes: A Problem-Solution Approach, 2005, Apress
    <http://www.torfree.net/~chris/books/cfaj/ssr.html>