POSIX Find – Limit Search to Specific Depth

The explanation of what the manual says is this:

When find gets to a directory that matches your -path expression, -prune will avoid going inside it. So find will go

/             ok, go inside
/home         ok, go inside
/home/xxxx    ok, go inside
/tmp          don't go inside
/var          ..etc...

But when you use -depth, it processes the inside of directories before the directories themselves. So it will match the path when it's too late:

/home/xxxx
/home         ok, go inside (it already went)
/tmp/zzzz     didn't match "-path /tmp", so it's ok
/tmp          don't go inside (too late!)
/var          ..etc...
/

To solve this problem you can try:

1. Just add new -path expressions with wildcards. This has the disadvantage that those subdirectories will be traversed anyway, just not printed (and their traversal will maybe trigger warnings)

   find ... \( -path './sys' -o -path './sys/*' -o -path './dev' -o -path './dev/*' ... \) -prune ...

2. Don't enumerate the directories to avoid, enumerate the ones to print!

   find /bin /boot /etc /home /lib ...

Note that POSIX find does support options like other commands, and -- to mark the end of them like other commands. Those are -H and -L.

The -print, -type... are not options, they're sometimes called predicates. They are arguments whose order matters that appear after the file paths which themselves appear after the options. You've also got ( and !. Together, they build an expression that is used to determine what files to find.

find is not the only one. [ (aka test) and expr are other commands whose arguments are used to build an expression.

Like find, [ has operators that start with - and are more than one-letter (-gt, -eq...).

Like find, test has issues where those operators may be confused with operands.

find -- "$file1" "$file2" -type f
[ -f "$file1" -a -f "$file2" ]

If $file2 is !, it's a problem with find. If it's =, it's a problem with (some) [.

For all of find, test and expr, using options to build the expression would not really have worked. Another option could have been to have one string evaluated as the expression like awk or sed. like for

find f1 f2 \( -type f -mtime -1 -o ! -type f -newer x \) -exec ls -ld {} +

Do:

find 'found = 0
      if (typeof($f) == "f") {
        if (age($f) > 1) found=1
      } else if (age($f) < age("x")) found = 1
      if ($found) exec_multi("ls -ld {}")' f1 f2

But that means implementing a grammar parser in find. That also means potential quoting nightmare for the "x" and command line above.

Actually AT&T Research did come up with such a command: tw (tree walker), but even though it's now open source, I'm not aware that it is really used out of AT&T.