In bash tee is making function variables local, how do I escape this?

问题

I have stucked with a bash scipt which should write both to stdout and into file. I'm using functions and some variables inside them. Whenever I try to redirect the function to a file and print on the screen with tee I can't use the variables that I used in function, so they become local somehow. Here is simple example:

#!/bin/bash
LOGV=/root/log

function var()
{
echo -e "Please, insert VAR value:\n"
read -re VAR
}
var 2>&1 | tee $LOGV
echo "This is VAR:$VAR"

Output:

[root@testbox ~]# ./var.sh   
Please, insert VAR value:

foo
This is VAR:
[root@testbox ~]#

Thanks in advance!

EDIT: Responding on @Etan Reisner suggestion to use var 2>&1 > >(tee $LOGV)

The only problem of this construction is that log file dosn't receive everything...

[root@testbox~]# ./var.sh
Please, insert VAR value: 

foo 
This is VAR:foo
[root@testbox ~]# cat log 
Please, insert VAR value:

回答1:

This is a variant of BashFAQ #24.

var 2>&1 | tee $LOGV

...like any shell pipeline, has the option to run the function var inside a subprocess -- and, in practice, behaves this way in bash. (The POSIX sh specification leaves the details of which pipeline components, if any, run inside the parent shell undefined).

---

Avoiding this is as simple as not using a pipeline.

var > >(tee "$LOGV") 2>&1

...uses process substitution (a ksh extension adopted by bash, not present in POSIX sh) to represent the tee subprocess through a filename (in the form /dev/fd/## on modern Linux) which output can be redirected to without moving the function into a pipeline.

---

If you want to ensure that tee exits before other commands run, use a lock:

#!/bin/bash
logv=/tmp/log

collect_var() {
        echo "value for var:"
        read -re var
}
collect_var > >(logv="$logv" flock "$logv" -c 'exec tee "$logv"') 2>&1
flock "$logv" -c true # wait for tee to exit

echo "This is var: $var"

---

Incidentally, if you want to run multiple commands with their output being piped in this way, you should invoke the tee only once, and feed into it as appropriate:

#!/bin/bash
logv=/tmp/log
collect_var() { echo "value for var:"; read -re var; }

exec 3> >(logv="$logv" flock "$logv" -c 'exec tee "$logv"') # open output to log
collect_var >&3 2>&3         # run function, sending stdout/stderr to log
echo "This is var: $var" >&3 # ...and optionally run other commands the same way
exec 3>&-                    # close output
flock "$logv" -c true        # ...and wait for tee to finish flushing and exit.

来源：https://stackoverflow.com/questions/31551115/in-bash-tee-is-making-function-variables-local-how-do-i-escape-this