mkhaw@teknowledge-vaxc.ARPA (Mike Khaw) (11/23/88)
If I have an inode (and fs root) on hand, how do I tell whether that
inode is a directory or not? The definition of struct inode suggests
that it's possible, but I can't find a man entry that says how.
If it matters, this would be for SunOS 3.x and Ultrix 2.x
Thanks,
Mike Khaw
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In article <25943@teknowledge-vaxc.ARPA> mkhaw@teknowledge-vaxc.ARPA (Mike Khaw) writes: >If I have an inode (and fs root) on hand, how do I tell whether that >inode is a directory or not? The definition of struct inode suggests >that it's possible, but I can't find a man entry that says how. Assuming you have already figured out how to find the disk block containing the start of the inode, the start of an inode on disk normally consists of essentially the same information that would be returned for stat(2) or fstat(2) and a handful of pointers to the data blocks associated with the inode. (Slightly oversimplified.) There is often a system header file <sys/inode.h> that describes the on-disk inode structure; watch out, because it typically includes descriptions of in-core (kernel) data structures, of which the disk inode information is only a part. Look in your System Administrator Reference Manual under FS(*) (where * depends on the vendor) for information about the file system.
ed@mtxinu.UUCP (Ed Gould) (11/24/88)
>If I have an inode (and fs root) on hand, how do I tell whether that >inode is a directory or not? The definition of struct inode suggests >that it's possible, but I can't find a man entry that says how. If inode.i_mode == IFDIR, then inode is a directory. -- Ed Gould mt Xinu, 2560 Ninth St., Berkeley, CA 94710 USA {ucbvax,uunet}!mtxinu!ed +1 415 644 0146 "I'll fight them as a woman, not a lady. I'll fight them as an engineer."
ron@ron.rutgers.edu (Ron Natalie) (11/24/88)
I'm not sure what you mean by "I have an inode." If you have the inode, the you look at the IFMT bits for IFDIR. Users don't normally get "inodes." What they can do is run "stat" on a file specification or fstat on an open file descriptor and get returned the inode information for that file. Again you check the IFMT bits. -Ron
mkhaw@teknowledge-vaxc.ARPA (Mike Khaw) (11/24/88)
> I'm not sure what you mean by "I have an inode." If you have the
Sorry: an int that represents an inode number.
Mike Khaw
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>If I have an inode (and fs root) on hand, how do I tell whether that >inode is a directory or not? The definition of struct inode suggests >that it's possible, but I can't find a man entry that says how. > >If it matters, this would be for SunOS 3.x and Ultrix 2.x It doesn't matter greatly; both those systems use the 4.2BSD file system, but Berkeley pretty much left the part of the inode that comes into play here alone, so the same technique can be used on V7/4.1BSD/S5 file systems. I presume (since you refer to "struct inode") by "inode" you mean "inode structure", either on disk or in core, rather than inumber. If you have an inumber, you have to get the inode structure first.... The "i_mode" field of the inode is laid out the exact same way the "st_mode" field of a "stat" structure is. Even the bits used in that field are the same in most UNIX implementations; you shouldn't, and don't have to, rely on this, however. Just check whether (i_mode & IFMT) == IFDIR (the analogy of checking whether "(st_mode & S_IFMT) == S_IFDIR)" for a "stat" structure).
guy@auspex.UUCP (Guy Harris) (11/26/88)
>Sorry: an int that represents an inode number.
In that case, life gets more complicated; you have to open the file
system (which means you have to figure out which device it is - if you
have only the major/minor, you'd have to scan "/dev" looking for the
appropriate block special file) and decipher the i-list. This is not
*too* painful for a V7/S5 file system; it's more work for a 4.2BSD file
system.
Note also that if the file system in question is, say, an NFS or RFS
file system, you're probably out of luck.