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It ensures that all I/O streams are accounted-for/occupied.

This way, the backgrounded process has nothing "tied" to the terminal so you can go about your business like you didn't do anything; nothing gets hung.

In this case, since you're launching the process over ssh from inside a shell script, it's making sure that there's nothing in that command that would prevent the script from moving on.

It ensures that all I/O streams are accounted-for/occupied.

This way, the backgrounded process has nothing "tied" to the terminal so you can go about your business without your program trying to read from TTY, which would cause the terminal to hang.

In this case, since you're launching the process over ssh from a shell script, it's making sure that the script can move along unencumbered.

It ensures that all I/O streams are accounted for.

This way, the backgrounded process has nothing "tied" to the terminal so you can go about your business like you didn't do anything; nothing gets hung.

In this case, since you're launching the process over ssh from inside a shell script, it's making sure that there's nothing in that command that would prevent the script from moving on.

It ensures that all I/O streams are accounted-for/occupied.

This way, the backgrounded process has nothing "tied" to the terminal so you can go about your business like you didn't do anything; nothing gets hung.

In this case, since you're launching the process over ssh from inside a shell script, it's making sure that there's nothing in that command that would prevent the script from moving on.

it's ensuring that the command is taking "nothing" as the input.

an example:

cat /dev/null > file.txt
# is the same as
printf '' > file.txt

would have the same result as deleting all the lines from a file.

guesses about myprogram:

• it could optionally accept something from stdin that it would prepend to foo.out; in this it's specifying that nothing's extra should be prepended.
• the author wants to to make sure that they're locking down all streams

the later is the goal in the example mentioned; it ensures that there can be no ties to the backgrounded process so that it won't cause any trouble on logout. Basically, it making sure that there's nothing to keep the terminal hung, so you can launch a background process over ssh, making sure that this unfinished process does not maintain any ties that will keep the session open.

It ensures that all I/O streams are accounted for.

This way, the backgrounded process has nothing "tied" to the terminal so you can go about your business like you didn't do anything; nothing gets hung.

In this case, since you're launching the process over ssh from inside a shell script, it's making sure that there's nothing in that command that would prevent the script from moving on.