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Size: 799
Comment: don't use [ -a ], since Posix leaves the behaviour of test unspecified when there are more than four arguments
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Size: 1040
Comment: Make the expression & explanation a bit easier (IMO) for newbies to read
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| Deletions are marked like this. | Additions are marked like this. |
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| if [[ -L $symlink && ! -e $symlink ]]; then echo "$symlink is dangling" |
if [[ ( -L $name ) && ( ! -e $name ) ]] then echo "$name is a dangling symlink" |
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| 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. | The Bash man page tells you that "`-L`" returns "True if file exists and is a symbolic link", and "`-e`" returns "True if file exists". What might not be clear is that "`-L`" considers "file" to be the link itself. To "`-e`", however, "file" is the '''target''' of the symlink (whatever the link is pointing to). That's why you need both tests to see if a symlink is dangling; "`-L`" checks the link itself, and "`-e`" checks whatever the link is pointing to. |
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| POSIX has these same tests, with the same semantics, so it can also be done with the `[` command: | POSIX has these same tests, with similar semantics, so if for some reason you can't use the (preferred) `[[` command, the same test can be done using the older `[` command: |
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| if [ -L "$symlink" ] && [ ! -e "$symlink" ]; then echo "$symlink is dangling" |
if [ -L "$name" ] && [ ! -e "$name" ] then echo "$name is a dangling symlink" |
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 $name ) && ( ! -e $name ) ]] then echo "$name is a dangling symlink" fi
The Bash man page tells you that "-L" returns "True if file exists and is a symbolic link", and "-e" returns "True if file exists". What might not be clear is that "-L" considers "file" to be the link itself. To "-e", however, "file" is the target of the symlink (whatever the link is pointing to). That's why you need both tests to see if a symlink is dangling; "-L" checks the link itself, and "-e" checks whatever the link is pointing to.
POSIX has these same tests, with similar semantics, so if for some reason you can't use the (preferred) [[ command, the same test can be done using the older [ command:
# POSIX if [ -L "$name" ] && [ ! -e "$name" ] then echo "$name is a dangling symlink" fi