On Sun, Sep 12, 2010 at 9:07 PM, Parmenides <mobile.parmenides@xxxxxxxxx> wrote: > 2010/9/12 Mulyadi Santosa <mulyadi.santosa@xxxxxxxxx>: >> On Sun, Sep 12, 2010 at 00:28, Parmenides <mobile.parmenides@xxxxxxxxx> wrote: >>> Hi, >>> >>> For a specified directory, we can go through it when the kernel >>> parsing path, though we can not read it. Actually, parsing path also >>> need read the directory file. So, how does the kernel distinguish >>> between these two permission? >> > Sorry for replying so late due to some trifles. For a directory, if it > is allowed to read, that means we can list all items in its directory > file, namely that we can read it completely. May be I understood the question wrong.... but you can't "ls" in a directory if it doesn't have execute permission. Or rather even if a directory has read/exectue permission you can't ls on it till all the directories in its path have execute permission. Is there something else that you are asking ? /home/mkatiyar/codetree/main> cd /tmp /tmp> mkdir -p a/b/c/d /tmp> ls -lR a a: total 4 drwxr-xr-x 3 mkatiyar mkatiyar 4096 2010-09-12 22:26 b a/b: total 4 drwxr-xr-x 3 mkatiyar mkatiyar 4096 2010-09-12 22:26 c a/b/c: total 4 drwxr-xr-x 2 mkatiyar mkatiyar 4096 2010-09-12 22:26 d a/b/c/d: total 0 /tmp> chmod 000 a/b /tmp> ls -lR a a: total 4 d--------- 3 mkatiyar mkatiyar 4096 2010-09-12 22:26 b ls: cannot open directory a/b: Permission denied /tmp> cd a/b ksh: cd: a/b: [Permission denied] /tmp> ls a/b ls: cannot open directory a/b: Permission denied > If it is allowed to > execute, that means we can go through it in a process of path parsing. > Path parsing will open every directory in a specified path. For > example, when parsing a path like /home/parmenides/src/hello.c, the > kernel will open a sequence of directory files, namely /, /home, > /home/parmenides and /home/parmenides/src, and read its subdirectory > for each. So, both of read permission and executing permission mean > that the kernel need to read the corresponding directory file. As > such, the common 'readable' has two meanings for a directory. One > corresponds to read the directory file when listing it, the other > corresponds to read the directory file when paring path. > > On the other hand, system call opendir(const char *pathname) has no > way to distinguish these two meanings whereas both listing and path > parsing need call opendir(). My quesition is exactly that how these > two permissions take their effect. > > -- > To unsubscribe from this list: send an email with > "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx > Please read the FAQ at http://kernelnewbies.org/FAQ > > -- Thanks - Manish ================================== [$\*.^ -- I miss being one of them ================================== -- To unsubscribe from this list: send an email with "unsubscribe kernelnewbies" to ecartis@xxxxxxxxxxxx Please read the FAQ at http://kernelnewbies.org/FAQ
