How to perform a shell redirection (command > output.txt) using ProcessBuilder?

Question

I wanted to backup a MySQL database using ProcessBuilder and the > character is not being interpreted as I expected. This is my code:

java.util.List<String> cmd = new java.util.ArrayList<>();
cmd.add("mysqldump");
cmd.add("-u");
cmd.add("root");
cmd.add("-p"+password);
cmd.add("DBx");
cmd.add(">");
cmd.add("DBbk.sql");

ProcessBuilder pb = new ProcessBuilder(cmd);
pb.directory(new File("."));
Process p = pb.start();
p.waitFor();

BufferedReader err = new BufferedReader(new InputStreamReader(p.getErrorStream()));
while((line = err.readLine()) != null) {
    System.out.println(line);
}

The output is:

Warning: Using a password on the command line interface can be insecure.
mysqldump: Couldn't find table: ">"

Redirection is a shell function. You appear to be running mysqldump directly, so redirection will not apply. — Jim Garrison
– Jim Garrison, Commented Oct 4, 2013 at 3:17

tbodt · Accepted Answer · 2013-10-04 03:17:27Z

7

The process builder is executing the program directly, not executing it through a shell/command prompt. Therefore, you don't get any nice features of the shell like the > character for redirection. Sorry.

answered Oct 4, 2013 at 3:17

tbodt

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Comments

Mosty Mostacho · Accepted Answer · 2013-10-04 03:28:53Z

1

Give this a try (just displaying the significant portion of the solution):

new ProcessBuilder("cmd", "/C", "your_command > DBbk.sql").start()

This way you're explicitly calling cmd. In Linux you could call bash or whatever shell you use.

answered Oct 4, 2013 at 3:28

Mosty Mostacho

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