ghe@physics.orst.edu (Guangliang He) (05/04/91)
The title pretty much said it all. The remove() system call fails to remove
the sybolic links. The man page of remove() did mention anything special
about symolic links.
Here is a little program shows the problem:
------
#include <stdio.h>
main(int argc, char **argv)
{
if (remove(argv[1]))
fprintf(stderr, "can't remove %s\n", argv[1]);
}
------
It works fine (no error message) with regular files but prints the
'can't remove.." message on symbolic links.
Is it a bug or 'work as designed' :-(???
---
Guangliang He | If anything can go wrong, it will.
ghe@physics.orst.edu | -- Murphy's Lawshore@theory.tn.cornell.edu (Melinda Shore) (05/04/91)
In article <1991May03.174126.13324@lynx.CS.ORST.EDU> ghe@physics.orst.edu writes: >The remove() system call fails to remove >the sybolic links. It should work as advertised. I *strongly* recommend checking errno after the system call fails either by using perror(), or looking at the value of errno yourself. You do want to know why remove() is failing, don't you? -- Software longa, hardware brevis Melinda Shore - Cornell Information Technologies - shore@theory.tn.cornell.edu
ghe@physics.orst.edu (Guangliang He) (05/04/91)
In article <1991May3.185244.1275@batcomputer.tn.cornell.edu>, shore@theory.tn.cornell.edu (Melinda Shore) writes: |> In article <1991May03.174126.13324@lynx.CS.ORST.EDU> ghe@physics.orst.edu writes: |> >The remove() system call fails to remove |> >the sybolic links. |> |> It should work as advertised. Which way??? should remove or not??? TFM did not mention a single word on symbolic links. |> I *strongly* recommend checking errno |> after the system call fails either by using perror(), or looking at the |> value of errno yourself. You do want to know why remove() is failing, |> don't you? Yes. I DO want to know why. But TFM says nothing about errno. It only mentioned that 0 is returned upon successful completion, and non-zero otherwise. When I try to call remove(b) ('b' is a symbolic link to a directory 'a'), perror prints: remove: Not a directory I still don't know why. |> -- |> Software longa, hardware brevis |> Melinda Shore - Cornell Information Technologies - shore@theory.tn.cornell.edu --- Guangliang He | If anything can go wrong, it will. ghe@physics.orst.edu | -- Murphy's Law
shore@theory.tn.cornell.edu (Melinda Shore) (05/04/91)
In article <1991May03.202209.432@lynx.CS.ORST.EDU> ghe@physics.orst.edu writes: >Which way??? should remove or not??? TFM did not mention a single word on >symbolic links. I just checked MFM and it says that "if the named file is a symbolic link to another file or directory, unlink [aka remove - ms] removes the symbolic link, not the file or directory to which it refers." Note the lengthy listings of error conditions at the end of the man page. > But TFM says nothing about errno. It only >mentioned that 0 is returned upon successful completion, and non-zero >otherwise. errno is a Unix thing, and you need to be familiar with it if you're writing code that makes system calls and you want that code to be reasonably robust. >When I try to call remove(b) ('b' is a symbolic link to a directory 'a'), >perror prints: >remove: Not a directory Probably because there's something wrong with either the pathname you're passing to your program or the pathname your symlink points to. Does your program have the same problem with all symlinks? -- Software longa, hardware brevis Melinda Shore - Cornell Information Technologies - shore@theory.tn.cornell.edu
wangh@beasley.CS.ORST.EDU (Haiyan Wang) (05/04/91)
In article <1991May3.212509.6542@batcomputer.tn.cornell.edu> shore@theory.tn.cornell.edu (Melinda Shore) writes: >In article <1991May03.202209.432@lynx.CS.ORST.EDU> ghe@physics.orst.edu writes: >>Which way??? should remove or not??? TFM did not mention a single word on >>symbolic links. > >I just checked MFM and it says that "if the named file is a symbolic >link to another file or directory, unlink [aka remove - ms] removes >the symbolic link, not the file or directory to which it refers." >Note the lengthy listings of error conditions at the end of the man >page. Are you sure you're reading AIX3.1 manual of remove()? I saved the man page into a file and searched the file with grep and could not find the word symbolic. Maybe the man page on our system is screwed up somehow? :-(. > >> But TFM says nothing about errno. It only >>mentioned that 0 is returned upon successful completion, and non-zero >>otherwise. > >errno is a Unix thing, and you need to be familiar with it if you're >writing code that makes system calls and you want that code to be >reasonably robust. > >>When I try to call remove(b) ('b' is a symbolic link to a directory 'a'), >>perror prints: >>remove: Not a directory > >Probably because there's something wrong with either the pathname >you're passing to your program or the pathname your symlink points >to. Does your program have the same problem with all symlinks? It is not likely to have something wrong with the pathname. I used the same program on other files and work fine. And same problem happened on different symbolic links. >-- > Software longa, hardware brevis >Melinda Shore - Cornell Information Technologies - shore@theory.tn.cornell.edu Guangliang He ghe@physics.orst.edu I'm using someonelse's account over the weekend.
web@farpoint.austin.ibm.com (Bill Baker) (05/06/91)
||> In article <1991May03.202209.432@lynx.CS.ORST.EDU> ghe@physics.orst.edu writes: ||> >The remove() system call fails to remove ||> >the sybolic links. ||> | |When I try to call remove(b) ('b' is a symbolic link to a directory 'a'), |perror prints: | |remove: Not a directory | |I still don't know why. Remove is implemented in libc. It calls unlink or rmdir to remove files or directories. To determine which to do, it calls stat. And therein lies the problem. If it's a symlink to a directory, stat follows the link and the code tries to rmdir the symlink. Naturally, the rmdir system call fails with ENOTDIR. This is also a problem if the object is a dangling symbolic link. The code should use lstat, not stat. BUG! web --- -- Bill Baker Internet: web@glasnost.austin.ibm.com IBM PSP AWD net: web@farpoint.austin.ibm.com 11400 Burnet Rd. VNET: WEBAKER AT AUSVMQ Austin, TX; 78758-2502