Read filename from command line argument

Question

I have in my code a hardcoded name for a text file I am reading.

String fileName = "test.txt";

However I now have to use a command argument like so:

 text.java arg1 arg2 arg3 (can be any amount) < test.txt

Can anyone help me please?

I have it getting the arguments no problem just not sure on the file. Thank you

I have tried:

String x = null;
        try {
            BufferedReader f = new BufferedReader(new InputStreamReader(System.in));

            while( (x = f.readLine()) != null )
            {
               System.out.println(x);
            }
        }
               catch (IOException e) {e.printStackTrace();}
               System.out.println(x);
              }

However my application now hangs on readLine, any ideas for me to try please?

This way, you only pass the content of test.txt to the standard input, not the file name. — Gábor Bakos, Jan 15 '14 at 22:02
@GaborBakos ah that makes more sense, I wrote the code to read it based on the name. Thanks — Natalie Carr, Jan 15 '14 at 22:05
@MariuszS I use for (int j = 0; j < ags.length; j++){ //do something} That part is working fine, It was the file I was having issues with :) — Natalie Carr, Jan 15 '14 at 22:05
Duplicate of: http://stackoverflow.com/questions/1431551/command-line-pipe-input-in-java — Brian Roach, Jan 15 '14 at 22:05

Stefano Sanfilippo · Answer 1 · 2014-01-15T22:09:05.427

2

That is because the file is not passed as an argument, but piped as standard input.

If that is the intended use (to pipe the content of the file), then you just have to read it from System.in (in means standard input):

public static void main(String[] args) throws IOException {
    BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
    String firstLine = in.readLine();
    // etc.
}

If you just wanted to pass the file name, then you have to remove or escape that <, because it means "pipe" in shell.

edited Jan 15 '14 at 22:09

answered Jan 15 '14 at 22:02

Stefano Sanfilippo

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It seems to hang on the readLine although there is no error, would you have any idea why it would do this? – Natalie Carr Jan 15 '14 at 22:34

score 0 · Answer 2 · answered Jan 15 '14 at 22:07

0

Pass the file as filename to your program and then open this file and read from it.

answered Jan 15 '14 at 22:07

MariuszS

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Read filename from command line argument

2 Answers2