Shell Programming and Scripting

Here is what I have.
1 main program and it calls several child programs. Each child has its own log file. I want all child logs also to be appended to the main.log so that I have a single log file. I also need individual child logfiles in tact for debug purposes. Need to be able to tail one log file instead of tens of child logs as they run..
I am free to modify either child or main program to accomplish this. How do it do this?

main.sh
log=main.log
echo "Entering main .log" >> $log
child1.sh

child1.sh
log=child.log
echo "this is child1" >> $log

give main.log a specific name like mainLog=main.log
and at end of child1.sh
cat $log >> $mainLog
this should solve the purpose

Unfortunately I cannot as main runs so many number of times in a day. I have every log file named as main_$now.log and child as child_$now.log where now is date + %ymdhms% format.

It always helps to know what Shell you are running.

I think that the unix "tee" command can be used to achieve the desired effect providing that every child log is written to by a unix Shell redirect (i.e. not directly by a program). The unix "tee" command splits the input from a pipe into two directions (like a tee-piece in plumbing).

Code:

echo "Log entry" | tee combined.log >> child.log

This approach is not suitable for high-intensity logs or mission-critical logs because Shell is not 100% reliable with concurrent writes to the same file.
The technique is very good for creating a central server log of say service ups and downs.

I tried tee but its not able to write to the combined.log as its already opened by the main.sh.