Is it possible to use "/" in a filename?
The answer is that you can't, unless your filesystem has a bug. Here's why:
There is a system call for renaming your file defined in fs/namei.c called renameat:
SYSCALL_DEFINE4(renameat, int, olddfd, const char __user *, oldname, int, newdfd, const char __user *, newname)When the system call gets invoked, it does a path lookup (do_path_lookup) on the name. Keep tracing this, and we get to link_path_walk which has this:
static int link_path_walk(const char *name, struct nameidata *nd){ struct path next; int err; unsigned int lookup_flags = nd->flags; while (*name=='/') name++; if (!*name) return 0;...This code applies to any file system. What's this mean? It means that if you try to pass a parameter with an actual '/' character as the name of the file using traditional means, it will not do what you want. There is no way to escape the character. If a filesystem "supports" this, it's because they either:
- Use a unicode character or something that looks like a slash but isn't.
- They have a bug.
Furthermore, if you did go in and edit the bytes to add a slash character into a file name, bad things would happen. That's because you could never refer to this file by name :( since anytime you did, Linux would assume you were referring to a nonexistent directory. Using the 'rm *' technique would not work either, since bash simply expands that to the filename. Even rm -rf wouldn't work, since a simple strace reveals how things go on under the hood (shortened):
$ ls testdirmyfile2 out$ strace -vf rm -rf testdir...unlinkat(3, "myfile2", 0) = 0unlinkat(3, "out", 0) = 0fcntl(3, F_GETFD) = 0x1 (flags FD_CLOEXEC)close(3) = 0unlinkat(AT_FDCWD, "testdir", AT_REMOVEDIR) = 0...Notice that these calls to unlinkat would fail because they need to refer to the files by name.