shell variable value in for loop different after loop I have a challenge with a variable value changed in a for loop and the value of that variable after the for loop and using tee SCRIPT_1: STATUS=9 for SESSION in A B C do STATUS=5 echo "SESSION=$SESSION STATUS=$STATUS" done echo "STATUS=$STATUS" output script_1 is: SESSION=A STATUS=5 SESSION=B STATUS=5 SESSION=C STATUS=5 STATUS=5 SRIPT_2: STATUS=9 for SESSION in A B C do STATUS=5 echo "SESSION=$SESSION STATUS=$STATUS" done | tee /tmp/ses.txt echo "STATUS=$STATUS" output_2 is: SESSION=A STATUS=5 SESSION=B STATUS=5 SESSION=C STATUS=5 STATUS=9 Why a different output when using tee after done command.

When you put a "| tee", the shell that is interpreting the script is forking a new shell for the loop. Inserting a sleep in the loop and launching the script in background gives this list of processes:


PID TTY TIME COMMAND
21168 pts/0 0:00 sh
21259 pts/0 0:00 ps
11962 pts/0 0:00 sh
21170 pts/0 0:00 sleep
21171 pts/0 0:00 tee
21169 pts/0 0:00 sh


As you can see, there is an additional shell at the end of the list. You can get the same result with this script:


STATUS=9
echo "" > /tmp/ses.txt
for SESSION in A B C
do
STATUS=5
echo "SESSION=$SESSION STATUS=$STATUS" | tee -a /tmp/ses.txt
done
echo "STATUS=$STATUS"


but whitout the side effect you are mentioning.