I can write to and read from a file:

```
echo a > b.txt
read c < b.txt

```

Is Bash able to do this implicitly? Something like:

```
<turn on implicit mode>
echo a
read c
<turn off implicit mode>

```

While “implicit mode” is on, all *stdout* goes to *b.txt* and all *stdin* reads
from *b.txt*. I tried:

```
exec > b.txt

```

but it only affects *stdout*.