Feature request: Command queue via file

[galiagante]

Sample use case:

A file containing nuanced/complex commands (e.g.):

cat commands.list

echo "one" && du -hcs ./one
echo "two" && du -hcs ./two
echo "three" && du -hcs ./three

To be executed in parallel like so:

parallel < commands.list

This would reproduce a useful command-line behavior similar to what's found in recent version of GNU Parallel.

As a work-around, perhaps there's a way to do this in the current version using an alternate syntax?

[mmstick]

It works if you enter target/debug/parallel :::: inputs or target/debug/parallel ::: < inputs but I can look into it.

[mmstick]

This is a mental note on the topic:

I think only a limited number of operating systems could use this feature (Linux + BSD). I see that it is possible to determine the owner of stdin on *nix systems that feature a proc filesystem by using the readlink function on /proc/self/fd/0. If the link points to /dev/pts then there probably isn't any redirection, but if it points to something else then there is input redirection. IE:

$ readlink /proc/self/fd/0
/dev/pts/4
$ readlink /proc/self/fd/0 < inputs
/home/mmstick/Sources/parallel/inputs

[mmstick]

This feature has now been implemented. There's three ways to do this now:

parallel :::: inputs.list
parallel < inputs.list
parallel ::: < inputs.list

Also discovered a bug where inputs as commands wasn't working as intended, which is now fixed.

e723442

[mmstick]

Relevant source code for detecting input redirection in Rust:

pub fn input_was_redirected() -> Option<PathBuf> {
    if let Ok(link) = fs::read_link("/proc/self/fd/0") {
        if !link.to_string_lossy().starts_with("/dev/pts") {
            return Some(link)
        }
    }
    None
}