Java Reference
In-Depth Information
1.3.9
If someone compiled a list of the top 10 most useful Linux utilities,
find
would
most likely be near the top of the list. But it would also make the top 10 most
confusing. Its syntax is very unlike other Linux utilities. It consists of
predicates
—logical expressions that cause actions and have true/false values that
determine if the rest of the expression is executed. Confused? If you haven't
used
find
before you probably are. We'll try to shed a little light by showing a
few examples.
The find Command
find . -name '*frag*' -print
This command looks for a file whose name contains
frag
. It starts looking in
the current directory and descends into all subdirectories in its search.
find /over/there . /tmp/here -name '*frag*.java' -print
This command looks for a file that has
frag
in its name and ends with
.java
.
It searches for this file starting in three different directories—the current
directory (“
.
”),
/over/there
, and
/tmp/here
.
find . -name 'My[A-Z]*.java' -exec ls -l '{}' \;
Starting in the current directory, this command searches for a file whose name
begins with
My
followed by an uppercase alphabetic character followed by
anything else, ending with
.java
. When it finds such a file, it will execute a
command—in this case, the
ls
command with the
-l
option. The braces are
replaced with the name of the file that is found; the “
\;
” indicates to
find
the
end of the command.
The
-name
is called a predicate; it takes a regular expression as an argu-
ment. Any file that matches that regular expression pattern is considered
true
,
so control passes on to the next predicate—which in the first example is simply
-print
that prints the filename (to standard out) and is always
true
(but since
no other predicate follows it in this example, it doesn't matter). Since only the
names that match the regular expression cause the
-name
predicate to be
true
,
only those names will get printed.
There are other predicates besides
-name
. You can get an entire list by
typing
man find
at a command prompt, but Table 1.3 lists a few gems, to give
you a taste of what
find
can do.
Let's look at an example to see how they fit together:
