Bash mine script, please [closed]

Question

The script, in and of its self, is fairly self-explanatory. Can this script be further improved?

First iteration was writ upon OS X 10.5.8 Leopard, current iteration was run upon OS X 10.6.4 Snow Leopard with Safari 5.0.2 (6533.18.5). Also, any illumination as to why the first line ' if [ -f ] ' works, but ' if [ -f ~/Library/Safari/LocalStorage/*.localstorage ] ' generates an error? [yes, I am a bit of a Noob]

Code:

#! /bin/bash
# SafariClear0.0.6

if [ -f ]
then
cat /dev/null > ~/Library/Safari/LocalStorage/*.localstorage
rm -f ~/Library/Safari/LocalStorage/*.localstorage
fi

if [ -f ~/Library/Safari/LocalStorage/*.localstorage ]
then
echo "Oy vey!"  
fi
cd ~/Library/Safari/
cat /dev/null > WebpageIcons.db
cat /dev/null > TopSites.plist
cat /dev/null > LocationPermissions.plist
cat /dev/null > LastSession.plist
cat /dev/null > History.plist
echo "Clear"
exit

Answer 1

This looks like it will be closed out, not sure why, maybe because it's a programming question on Superuser.

1) the test [ -f ] doesn't make sense. The -f test is to test to see if something is a file and it exists. Having -f with no file does nothing.

2) Seeing if "a directory contains one or more files" is harder than it seems on first glance. Luckily you don't really need to. See #3 below.

3) The first chunk of code truncates files, which you then delete. Why bother truncating at all? Just delete them and be done with it. You can do:

find ~/Library/Safari/LocalStorage/ -type f -name '*.localstorage' -exec rm -f {} \;

4) You then truncate some other files. This can be looped, which may be an improvement.

cd ~/Library/Safari/
for FILE in WebpageIcons.db TopSites.plist LocationPermissions.plist LastSession.plist  History.plist
do
    cat /dev/null > $FILE
done

Joining those two code snippets into a script does everything your script does.

Answer 2

In [ -f *.txt ],

• If no such file exists,
  • if the shell option nullglob is not enabled (the default), the word *.txt remains unexpanded, and -f evaluates to false.
  • if the shell option nullglob is enabled, the word *.txt is removed, leaving [ -f ], which is equivalent to test -f. Since only 1 argument is given, the rule is that the expression is true if and only if the argument is not null. -f is not null, so the expression is true.
• If such files exist, *.txt is expanded to a list of their names.
  • If only one such file exists, -f sees the filename and evaluates to true.
  • If two such files exist, the third argument is expected to be a binary operator (-a or -o), and you probably get a binary operator expected error.
  • If three or more such files exist, you get a too many arguments error.

To test whether files matching a pattern exist, see this thread.