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ln: only check existence of src/to for hardlinks

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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
This commit is contained in:
Eivind Uggedal
2015-05-08 08:16:57 +00:00
committed by sin
parent 3f01706837
commit 8f4b2e8689
1 changed files with 6 additions and 7 deletions
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13
ln.c
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@@ -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);