How to lock a file on a Samba share during mutual access?

Question

I have a file on a Samba share and there are several computers which append data to the file. I need to lock this file by each computer in order to perform append operations sequentially. How can I achieve it?
The reason is that the file turns out complete mess at that moment. I've tried to play with Samba options but I couldn't solve this issue.

testparm:

[global]
    netbios name = XXXXXXX
    server string = %h server (Samba, Ubuntu)
    map to guest = Bad User
    obey pam restrictions = Yes
    pam password change = Yes
    passwd program = /usr/bin/passwd %u
    passwd chat = *Enter\snew\s*\spassword:* %n\n *Retype\snew\s*\spassword:* %n\n *password\supdated\ssuccessfully* .
    unix password sync = Yes
    syslog = 0
    log file = /var/log/samba/log.%m
    max log size = 1000
    dns proxy = No
    usershare allow guests = Yes
    panic action = /usr/share/samba/panic-action %d
    idmap config * : backend = tdb

[HwInfo]
    path = /home/XXXXXXXXX/hw/IN
    write list = all
    read only = No
    create mask = 0644
    guest ok = Yes

I created the next script:

STR="\n\n\n$1\n\n"

while : ; do
  echo -e $STR >> "./temp/info.csv"
done

and ran it in the several terminal sessions on the same computer simultaneously. "./temp" is the mount point for the Samba share.