[hackers] [sbase] ln: only check existence of src/to for hardlinks || Eivind Uggedal

From: <git_AT_suckless.org>
Date: Fri, 8 May 2015 11:07:03 +0200 (CEST)

commit 8f4b2e86892678a6916fffce142ac3807f563003
Author: Eivind Uggedal <eivind_AT_uggedal.com>
Date: Fri May 8 08:16:57 2015 +0000

    ln: only check existence of src/to for hardlinks
    
    This allows for creating dangling symlinks with force applied:
    
        # Before:
        $ ln -sf non-existant target
        ln: stat non-existent: No such file or directory
        $ ls -l target
        ls: lstat target: No such file or directory
    
        # After:
        $ ln -sf non-existant target
        $ ls -l target
        lrwxrwxrwx 1 eu users 12 May 08 07:50 target -> non-existent
    
    This also allows creating relative non-dangling symlinks with force applied:
    
        touch existant; mkdir dir
    
        # Before
        $ ln -sf ../existant dir
        ln: stat ../existant: No such file or directory
        $ ls -l dir
    
        # After
        $ ln -sf ../existant dir
        $ ls -l dir
        lrwxrwxrwx 1 eu users 11 May 08 07:53 existant -> ../existant
    
    The check for whether each src and to pairs are on the same device with the
    same inode are only needed for hardlinks so that a forcefull link does
    not remove the underlying file:
    
        touch f; mkdir dir
    
        # Before:
        $ ln -f f f dir
        ln: f and f are the same file
        $ ls -i f dir/f
        3670611 dir/f
        3670611 f
    
        # After:
        $ ln -f f f dir
        ln: f and f are the same file
        $ ls -i f dir/f
        4332236 dir/f
        4332236 f

diff --git a/ln.c b/ln.c
index b63e75c..2bfdbbd 100644
--- a/ln.c
+++ b/ln.c
_AT_@ -61,21 +61,20 @@ main(int argc, char *argv[])
         for (; *argv; argc--, argv++) {
                 if (!hasto)
                         to = basename(*argv);
- if (fflag) {
+ if (!sflag) {
                         if (stat(*argv, &st) < 0) {
                                 weprintf("stat %s:", *argv);
                                 continue;
                         } else if (fstatat(dirfd, to, &tost, AT_SYMLINK_NOFOLLOW) < 0) {
                                 if (errno != ENOENT)
                                         eprintf("stat %s:", to);
- } else {
- if (st.st_dev == tost.st_dev && st.st_ino == tost.st_ino) {
- weprintf("%s and %s are the same file\n", *argv, *argv);
- continue;
- }
- unlinkat(dirfd, to, 0);
+ } else if (st.st_dev == tost.st_dev && st.st_ino == tost.st_ino) {
+ weprintf("%s and %s are the same file\n", *argv, *argv);
+ continue;
                         }
                 }
+ if (fflag)
+ unlinkat(dirfd, to, 0);
                 if ((!sflag ? linkat(AT_FDCWD, *argv, dirfd, to, flags)
                             : symlinkat(*argv, dirfd, to)) < 0) {
                         weprintf("%s %s <- %s:", fname, *argv, to);
Received on Fri May 08 2015 - 11:07:03 CEST