Diff for "BashFAQ/097"

Differences between revisions 1 and 3 (spanning 2 versions)

How do I determine whether a symlink is dangling (broken)?

The documentation on this is fuzzy, but it turns out you can do this with shell builtins:

# Bash
if [[ -L $symlink && ! -e $symlink ]]; then
  echo "$symlink is dangling"
fi

The -e test (like all other tests besides -L or -h) follows the symbolic link, and therefore it checks on the thing pointed to, not on the link itself. The -L test does not follow the symlink, so it's checking on the link itself. Together, they can indicate the presence of a dangling symlink.

POSIX has these same tests, with the same semantics, so it can also be done with the [ command:

# POSIX
if [ -L "$symlink" ] && [ ! -e "$symlink" ]; then
  echo "$symlink is dangling"
fi

-  ⇤ ← Revision 1 as of 2009-02-10 14:57:37 → 
  Size: 590
  Editor: GreyCat
  Comment: How do I determine whether a symlink is dangling (broken)?
+   ← Revision 3 as of 2009-02-10 15:55:01 → ⇥
  Size: 799
  Editor: NeilMoore
  Comment: don't use [ -a ], since Posix leaves the behaviour of test unspecified when there are more than four arguments
-Deletions are marked like this.
+Additions are marked like this.
 Line 3:
-The documentation on this is fuzzy, but it turns out you ''can'' do this with bash builtins:
+The documentation on this is fuzzy, but it turns out you ''can'' do this with shell builtins:
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+POSIX has these same tests, with the same semantics, so it can also be done with the `[` command:

{{{
# POSIX
if [ -L "$symlink" ] && [ ! -e "$symlink" ]; then
  echo "$symlink is dangling"
fi
}}}