create a file with fallocate, values for it are store in files

in a linux-system in bash i will create a file with fallocate. not with full size, only mark in the filesystem with the size they i chose.

the size value is in temp/size and

the name value is in temp/name

in temp/decrypt/ will i store the file

i try something like this:

fallocate -l $(cat temp/size) temp/decrypt/"$(cat temp/name)"

but it doesnt work and i dont know what is wrong

cat temp/size
1073741824

and

cat temp/name
testname123.data

works, but where is the error?

:edit

fallocate failed: Operation not supported