Export tmsh command output to a file ex: txt

Calling tmsh commands directly from bash like Yann suggested is suitable in most cases, but might involve problems when using partitions. Another way to accomplish this would be starting an interactive tmsh as normal, but piping its output to file via tee like this:

bash> tmsh | tee myoutput.txt
root@(my_lb)(cfg-sync In Sync)(/S1-green-P:Active)(/Common)(tmos) cd /PA999-Test1/
root@(my_lb)(cfg-sync In Sync)(/S1-green-P:Active)(/PA999-Test1)(tmos) list net self
net self FLOATIP-VLAN4091 {
    address 10.44.55.250/24
    floating enabled
    partition PA999-Test1
    traffic-group /Common/TG999-Test1
    unit 2
    vlan VLAN4091
}
net self FLOATIP-VLAN4092 {
    address 10.22.33.240/24
    floating enabled
    partition PA999-Test1
    traffic-group /Common/TG999-Test1
    unit 2
    vlan VLAN4092
}
net self SELFIP-VLAN4092 {
    address 10.22.33.238/24
    partition PA999-Test1
    traffic-group /Common/traffic-group-local-only
    vlan VLAN4092
}
net self SELFIP-VLAN4091 {
    address 10.44.55.248/24
    partition PA999-Test1
    traffic-group /Common/traffic-group-local-only
    vlan VLAN4091
}
root@(my_lb)(cfg-sync In Sync)(/S1-green-P:Active)(/PA999-Test1)(tmos) quit   <--- back to bash
[root@my_lb:/S1-green-P:Active:In Sync] config 
[root@my_lb:/S1-green-P:Active:In Sync] config 
[root@my_lb:/S1-green-P:Active:In Sync] config  ls -lah myoutput.txt
-rw------- 1 root root 1.2K Jun  3 11:42 myoutput.txt    <--- This file contains all of your tmsh session