Someone always says this, but starting with cat sure makes it easier compose the command line. When working with big files, start with "head -1000 | sort | uniq ..." and switch to cat after you work out the command. Or you start composing the command and realize you need to sort on field 2, so insert a "cut" before the "sort" etc.

And for people like me who want the file name first on the line, this format works in Bash at least:

</dir/file sort | uniq >outfile

I always find it really confusing when the command-line begins with a redirect.

Yes, how do you parse that - ie. what does it even mean?

It's just a convention that redirects come after the command they're redirecting. There might be shell options that influence this, but I think all these are generally equivalent:

    foo bar < a
    foo < a bar
    < a foo bar

It is POSIX shell parsing behaviour that redirections can appear anywhere in the command (obviously, not in the same word as another parameter, nor inside a quoted string). They have to be stripped out by the shell before execution: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3...