I am getting an exception like java.io.IOException: Cannot run program cat /home/talha/* | grep -c TEXT_TO_SEARCH\": error=2, No such file or directory
while execut
Runtime.exec does not use a shell (like, say, /bin/bash
); it passes the command directly to the operating system. This means wildcards like *
and pipes (|
) will not be understood, since cat
(like all Unix commands) does not do any parsing of those characters. You need to use something like
p = new ProcessBuilder("bash", "-c", command).start();
or, if for some bizarre reason you need to stick to using the obsolete Runtime.exec methods:
p = Runtime.getRuntime().exec(new String[] { "bash", "-c", command });
If you are only running that cat/grep command, you should consider abandoning the use of an external process, since Java code can easily traverse a directory, read lines from each file, and match them against a regular expression:
Pattern pattern = Pattern.compile("TEXT_TO_SEARCH");
Charset charset = Charset.defaultCharset();
long count = 0;
try (DirectoryStream dir =
Files.newDirectoryStream(Paths.get("/home/talha"))) {
for (Path file : dir) {
count += Files.lines(file, charset).filter(pattern.asPredicate()).count();
}
}
Update: To recursively read all files in a tree, use Files.walk:
try (Stream tree =
Files.walk(Paths.get("/home/talha")).filter(Files::isReadable)) {
Iterator i = tree.iterator();
while (i.hasNext()) {
Path file = i.next();
try (Stream lines = Files.lines(file, charset)) {
count += lines.filter(pattern.asPredicate()).count();
}
};
}