find in directory that starts with dash

问题:

find interprets a dash at the start of a filename as the start of an option. Using the familiar -- trick doesn't work since options are after the filename, quoting has no effect, and replacing the first dash with \- doesn't work either. Users are often encouraged to precede such filenames with ./, but what can I do if I don't know whether the given path will be absolute or relative?

Edit: One solution is to find "$(readlink -f -- "$test_filename")", but it's ugly. Any better ideas?

Edit 2: Thanks for the suggestions. Here are the two scripts that resulted from this effort: safe-find.sh; safe-count-files.sh

回答1:

This may seem a bit cheap, but I actually recommend the readlink workaround that you've figured out. According to the Unix standard,

The first argument that starts with a '-' (...) and all subsequent arguments shall be interpreted as an expression

so -- will indeed not work. thkala's solution may also work, but I find it less readable. It may be faster though, if you're doing a lot of find invocations.

回答2:

If it is in a script you can always check for it. E.g. for bash, ksh or zsh:

if [[ "$DIR" = -* ]]; then
    find ./"$DIR"
else
    find "$DIR"
fi

In a more terse form (for bash, ksh93 or zsh):

find "${DIR/#-/./-}"

You can even do this with the parameters of a script, if they are all supposed to be directories:

find "${@/#-/./-}"

回答3:

Here is a way that should work on all Unix-like systems, with no requirement on a specific shell or on a non-standard utility¹.

case $DIR in
  -*) DIR=./$DIR;;
esac
find "$DIR" …

If you have a list of directories in your positional parameters and want to process them, it gets a little complicated. Here's a POSIX sh solution:

i=1
while [ $i -le $# ]; do
  case $1 in
    -*) x=./$1;;
    *) x=$1;;
  esac
  set -- "$@" "$x"
  shift
  i=$(($i + 1))
done
find "$@" …

Bourne shells and other pre-POSIX sh implementations lack arithmetic and set --, so it's a little uglier.

i=1
while [ $i -le $# ]; do
  x=$1
  case $1 in
    -*) x=./$1;;
  esac
  set a "$@" "$x"
  shift
  shift
  i=`expr $i + 1`
done
find "$@" …

¹ _{readlink -f is available on GNU (Linux, Cygwin, etc.), NetBSD ≥4.0, OpenBSD ≥2.2, BusyBox. It is not available (unless you've installed GNU tools, and you've made sure they're in your PATH) on Mac OS X (as of 10.6.4), HP-UX (as of 11.22), Solaris (as of OpenSolaris 200906), AIX (as of 7.1).}

回答4:

Use a glob to capture the dash:

find . -name '[-]*'

---

edit: updated to remove the phrase regular expression, and to quote the glob so it's interpreted by find, not bash (only affects some edge cases).