File content redirection without using cat
It is not uncommon that people have abused the command `cat` for many purpose, e.g. file I/O redirection
cat data.txt | sed 's/foo/bar/s'
You can avoid the cat command by the following commands:
data.txt < sed 's/foo/bar/s' sed 's/foo/bar/s' < data.txt
Both directions are okay.
In fact, when you better understand the usage of some commands, you might find out that redirection is completely not needed.
sed 's/foo/bar/s' data.txt