linux - Is it possible to use "/" in a filename? -

-

i know not should ever done, there way use slash character separates directories within filename in linux?

the answer can't, unless filesystem has bug. here's why:

there system call renaming file defined in fs/namei.c called renameat:

syscall_define4(renameat, int, olddfd, const char __user *, oldname,                 int, newdfd, const char __user *, newname)

when system call gets invoked, path lookup (do_path_lookup) on name. keep tracing this, , link_path_walk 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 file system. what's mean? means if try pass parameter actual '/' character name of file using traditional means, not want. there no way escape character. if filesystem "supports" this, it's because either:

  • use unicode character or looks slash isn't.
  • they have bug.

furthermore, if did go in , edit bytes add slash character file name, bad things happen. that's because never refer file name :( since anytime did, linux assume referring nonexistent directory. using 'rm *' technique not work either, since bash expands filename. rm -rf wouldn't work, since simple strace reveals how things go on under hood (shortened):

$ ls testdir myfile2 out $ strace -vf rm -rf testdir ... unlinkat(3, "myfile2", 0)               = 0 unlinkat(3, "out", 0)                   = 0 fcntl(3, f_getfd)                       = 0x1 (flags fd_cloexec) close(3)                                = 0 unlinkat(at_fdcwd, "testdir", at_removedir) = 0 ...

notice these calls unlinkat fail because need refer files name.


Comments

Post a Comment

Popular posts from this blog

c++ - No viable overloaded operator for references a map -

-
i trying use map can make tag names reference number. when try , use it, in code error (6 in total every time reference map): src/main.cpp:25:45: error: no viable overloaded operator[] type 'std::map<std::string, std::string>' const char* idcs = node.child_value(tagmap[3]); this code: #include "pugi/pugixml.hpp" #include <iostream> #include <string> #include <map> int main() { pugi::xml_document doca, docb; std::map<std::string, pugi::xml_node> mapa, mapb; std::map<std::string, std::string> tagmap {{"1", "data"}, {"2", "entry"}, {"3", "id"}, {"4", "content"}}; if (!doca.load_file("a.xml") || !docb.load_file("b.xml")) { std::cout << "can't find input files"; return 1; } (auto& node: doca.child(tagmap[1]).children(tagmap[2])) { co
Read more

java - Custom OutputStreamAppender not run: LOGBACK: No context given for <MYAPPENDER> -

-
i wish write custom appender on basis of outputstreamappender . wrote following class package tests; import java.io.ioexception; import java.io.outputstream; import ch.qos.logback.core.outputstreamappender; public class myappender<e> extends outputstreamappender<e> { public myappender() { system.out.println("myappender created"); setoutputstream(new outputstream() { @override public void write(int b) throws ioexception { throw new unsupportedoperationexception(); } }); } } then wrote following runner: package tests; import org.slf4j.loggerfactory; import ch.qos.logback.classic.logger; public class runner { private static final logger log = (logger) loggerfactory.getlogger(runner.class); public static void main(string[] args) { //log.addappender(new myappender<iloggingevent>()); log.info("hello world"); } } finall
Read more

java - Cannot secure connection using TLS -

-
i'm trying establish secure socket connection between java client applet (built jdk 1.7.0_75-b13) , vc++ server application. as test vehicle, used vc++ client/server sample found in msdn forums, modified use schannel , able establish socket using cipher suite tls_rsa_with_aes_128_cbc_sha. works of tls 1.0/1.1/1.2. when try opening socket java applet same server application, connection rejected server reporting following: tls 1.0 acceptsecuritycontext failed: 0x80090327 tls 1.1 acceptsecuritycontext failed: 0x80090331 tls 1.2 acceptsecuritycontext failed: 0x80090331 this java code used create socket: debugprint("setting secure connection"); sslsocketfactory sslsocketfactory = (sslsocketfactory) sslsocketfactory.getdefault(); sslsocket sslsocket = (sslsocket) sslsocketfactory.createsocket("127.0.0.1", socketnumber); debugprint("starting handshake"); sslsocket.settcpnodelay(true); sslsocket.setsolinger(false, 0); sslsocket.s
Read more