Unix/ls: Difference between revisions
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=={{header|Java}}==
This is a generic implementation using the basic ''File'' methods.
<syntaxhighlight lang="java">
import java.io.File;
import java.util.ArrayList;
import java.util.Formatter;
import java.util.List;
public class Ls {
public static void main(String[] args) throws Exception {
Ls ls = new Ls("/");
System.out.println(ls);
}
private final File directory;
private final List<File> list;
public Ls(String path) throws Exception {
directory = new File(path);
if (!directory.exists())
throw new Exception("Path not found '%s'".formatted(directory));
if (!directory.isDirectory())
throw new Exception("Not a directory '%s'".formatted(directory));
list = new ArrayList<>(List.of(directory.listFiles()));
/* place the directories first */
list.sort((fileA, fileB) -> {
if (fileA.isDirectory() && fileB.isFile()) {
return -1;
} else if (fileA.isFile() && fileB.isDirectory()) {
return 1;
}
return 0;
});
}
private String size(long bytes) {
if (bytes > 1E9) {
return "%.1fG".formatted(bytes / 1E9d);
} else if (bytes > 1E6) {
return "%.1fM".formatted(bytes / 1E6d);
} else if (bytes > 1E3) {
return "%.1fK".formatted(bytes / 1E3d);
} else {
return "%d".formatted(bytes);
}
}
@Override
public String toString() {
StringBuilder string = new StringBuilder();
Formatter formatter = new Formatter(string);
/* add parent and current directory listings */
list.add(0, directory.getParentFile());
list.add(0, directory);
/* generate total used space value */
long total = 0;
for (File file : list) {
if (file == null) continue;
total += file.length();
}
formatter.format("total %s%n", size(total));
/* generate output for each entry */
int index = 0;
for (File file : list) {
if (file == null) continue;
/* generate permission columns */
formatter.format(file.isDirectory() ? "d" : "-");
formatter.format(file.canRead() ? "r" : "-");
formatter.format(file.canWrite() ? "w" : "-");
formatter.format(file.canExecute() ? "x" : "-");
/* include size */
formatter.format("%7s ", size(file.length()));
/* modification timestamp */
formatter.format("%tb %1$td %1$tR ", file.lastModified());
/* file or directory name */
switch (index) {
case 0 -> formatter.format(".");
case 1 -> formatter.format("..");
default -> formatter.format("%s", file.getName());
}
if (file.isDirectory())
formatter.format(File.separator);
formatter.format("%n");
index++;
}
formatter.flush();
return string.toString();
}
}
</syntaxhighlight>
<pre>
total 22.3K
dr-x 154 Feb 13 02:48 ./
dr-x 10.9K Apr 14 20:17 ../
dr-x 0 Dec 09 14:15 boot/
dr-x 660 May 12 20:48 dev/
dr-x 2.3K May 12 20:48 etc/
dr-x 12 Apr 14 20:12 home/
dr-x 614 Apr 15 15:00 lib/
dr-x 1.1K Apr 15 15:00 lib32/
dr-x 46 Feb 13 02:48 lib64/
dr-x 1.1K Apr 15 15:00 libx32/
dr-x 0 Feb 13 02:47 media/
dr-x 32 Apr 14 20:12 mnt/
dr-x 40 Apr 14 20:18 opt/
dr-x 0 May 12 20:48 proc/
d--- 30 Feb 13 02:47 root/
dr-x 400 May 12 20:48 run/
dr-x 4.2K Feb 13 02:48 sbin/
dr-x 0 Feb 13 02:47 srv/
dr-x 0 May 12 20:48 sys/
drwx 566 May 13 00:41 tmp/
dr-x 116 Feb 13 02:47 usr/
dr-x 90 Feb 13 02:47 var/
</pre>
<br />
An alternate demonstration
{{Works with|Java|11}}
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