Get output from Bash in Java?

cg flag

I have this this Java code that works:

public class GetNumberOfFiles {
    protected long GetNumberOfFilesMethod(String folder){
        try {
            Process p = Runtime.getRuntime().exec(new String[]{"bash", "-c", "cd " + folder + "&& find . -type f | grep :*.txt "});
            BufferedReader stdInput = new BufferedReader(new InputStreamReader(p.getInputStream()));
            return stdInput.lines().count();
        } catch (IOException e) {
            throw new RuntimeException(e);


I created also this code with similar logic, but after a few tries I put the bash code into a separate file.

The Java code:

protected String CheckUserMethod(String user){
        try {

            Process p = Runtime.getRuntime().exec(new String[]{"bash", "-c", "~/Final-Year/src/query", "&& ./", user});
            BufferedReader srdInput = new BufferedReader(new InputStreamReader(p.getInputStream()));
            String a = null;
            while ((a = srdInput.readLine()) != null)

            return a;
        }catch (Exception e){
            throw new RuntimeException(e);

The bash code is:


# shellcheck disable=SC2237
if ! [ -z "$1" ]
  echo "$1"
  cd ~/Final-Year/maps/ && find "$1" -maxdepth 0 -type d -printf 1

The code is working perfectly when I am executing from terminal as it is in this example:

enter image description here

The problem is,when I am executing the code from Java is not even executing the bash file. Do you have any suggestion?

hr flag

When you use bash -c, the first argument after the -c is treated as a command, and any additional arguments are passed as positional parameters.

In your first fragment,

{"bash", "-c", "cd " + folder + "&& find . -type f | grep :*.txt "}

you are passing a single concatenated string argument "cd " + folder + "&& find . -type f | grep :*.txt " whereas in the second fragment,

{"bash", "-c", "~/Final-Year/src/query", "&& ./", user}

you are passing 3 arguments:

  • ~/Final-Year/src/query (which presumably should have been cd ~/Final-Year/src/query
  • && ./
  • user

so it's equivalent to

bash -c '~/Final-Year/src/query' '&& ./' user

which executes bash -c '~/Final-Year/src/query' or (corrected) bash -c 'cd ~/Final-Year/src/query' with literal string && ./ as positional parameter $0 and the substituted Java variable user as positional parameter $1

What you likely want is

bash -c 'cd ~/Final-Year/src/query && ./ user'

which would instead be

{"bash", "-c", "cd ~/Final-Year/src/query && ./ " + user}

Alternatively, you could make use of the positional parameter array like

{"bash", "-c", "cd ~/Final-Year/src/query && ./ \"$1\"", "bash", user}

where the shell's name bash is passed as $0 (you could use any arbitrary string here) and Java variable user as $1.

ilie alexandru avatar
cg flag
Apologies for the late response. Thank you so much for your help!
I sit in a Tesla and translated this thread with Ai:


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