How to use a variable to indicate a file descriptor in bash?

bash io exec file-descriptor

WH's HeV · Nov 28, 2011 · Viewed 8.6k times · Source

I want to use a bash variable to indicate a file descriptor, like this:

id=6
file=a
exec $id<>$file

But the usage is wrong:

-bash: exec: 6: not found

So, how to use a variable to indicate a file descriptor in exec command?

Answer

The accepted answer is correct, but as of bash 4.1, you can use automatic file descriptor allocation, and in that case you don't need eval:

file=a
exec {id}<>"$file"

Then you can use it like this:

echo  test >&${id}

or:

fsck -v -f -C ${id} /dev/something