#!/bin/sh

thisdir=`pwd`
usrname='username'
passwrd='password'

# There are several areas to fix, the username/password above, and the
# server/share name and dns name specifics below, the file to copy, and what
# that file should be called on this box once the copying is successful

# Correct   If a file doesn't exist, or the old file is deleted first, 
# Behavior  then the new file is copied to the desired location, during 
#           the time the file is being copied, we get an error, the 
#           destination file isn't created or modified, and things work
#           like they should.
#
# Problem:  When doing an SMB copy from a windows share at the same time a 
#           new file is being copied over top of an old one, the resulting 
#           copy we get is damaged (the file is zero'ed out from the point
#           where the new copy started being written over the old). 
#
# Solution: Attempt two copies of the file.  If a new file is being copied
#           over the top of the old one, the zero'ed out area(s) will make
#           the resulting files different, once the two files are identical,
#           and larger than zero bytes, then we can be assured that the 
#           copy was successful.

get_valid_smb_copy() {

    echo "Attempting to retrieve wlan.ini"

    if [ -f temp.1 ]; then
        rm temp.1
    fi
    if [ -f temp.2 ]; then
        rm temp.2
    fi

    #copy the wlan.ini file from the gcam server share (windows smb copy)
    /usr/bin/smbclient //server/sharename -I servers.dns.entry \
      -U $usrname%$passwrd -W workgrpORdomain -N -c "get file-to-copy temp.1"

    fn=1
    smbcnt=0

    while [ 0 = 0 ]; do

        # Nice little function to have $fn occilate between 1 and 2
        fn=`expr $fn % 2 + 1`
        
        # Remove old attempt before attempting to copy it again. This 
        # prevents problems when the file might disappear for a short 
        # time. The copy attempt fails, but the old file is then still 
        # left.  This way, what ever is in this file after the copy 
        # attempt is guaranteed to be the results of the most recent 
        # copy attempt.
        if [ -f temp.$fn ]; then
            rm temp.$fn
        fi

        /usr/bin/smbclient //server/sharename -I servers.dns.entry \
          -U $usrname%$passwrd -W workgrpORdomain -N -c "get file-to-copy temp.$fn"

        # If we're able to copy the file twice, and the destination files are identical 
        # and they are larger than 0 bytes, then I believe we can say with certainty, 
        # there have been no problems or errors while copying the files

        if [ -f temp.1 ] && [ -f temp.2 ] && [ ! -z temp.1 ] && [ ! -z temp.2 ]; then
            echo -n "  Got 2 copies..." 
            if ( cmp -s temp.1 temp.2 ); then
                echo "  Copies identical" 
                break
            else
                echo "  Copies not identical"
            fi
        fi

        smbcnt=`expr $smbcnt + 1`

        echo "  SMB Copy loop #$smbcnt"

        if (( $smbcnt == 50 )); then
            echo "Tried to get a valid SMB copy $smbcnt times, but failed; script exiting." 
            exit
        fi
        
        # Allow some small amount of time to pass before allowing the next 
        # attempt.  Otherwise 50 failures could pile up very quickly if the 
        # target file is deleted for a relatively short time.
        sleep 2

    done

    rm temp.2
    mv temp.1 resulting-file-name
}

    get_valid_smb_copy

    echo "File successfully copied to resulting-file-name"

exit