File as command line argument java

Java file input as command line argument

Solution 2: You cannot pass files as command line arguments, you have to pass file names as command line arguments and open that file in main function Solution 3: Assuming that you want to open the files, remember that in Java is an object that stores path and name information. Solution 1: You need to pass in the url of the files via command line and then create new files from the urls.

Java file input as command line argument

You should be able to read the input data from System.in .

Here’s some quick-and-dirty example code. javac Test.java; java Test < Test.java :

class Test < public static void main (String[] args) < byte[] bytes = new byte[1024]; try < while (System.in.available() >0) < int read = System.in.read (bytes, 0, 1024); System.out.write (bytes, 0, read); >> catch (Exception e) < e.printStackTrace (); >> > 

It seems any time you post a formal question about your problem, you figure it out.

Turns out you have to use the buffered reader class.

I’m not sure why you want to pass the contents of a file as command line arguments unless you’re doing some weird testbed.

You could write a script that would read your file, generate a temporary script in which the java command is followed by your needs.

Read system properties from file specified as java, 3 Answers. Sorted by: 1. You can read the properties file in bash (in run.sh file), parse properties and create the proper config line for JVM. Here you can find 2 articles that can help you: Reading Java-style Properties Files with Shell ( permalink) Reading java.properties file from bash. Share.

Passing a file as a Commandline argument in Java

I believe you will find that the ~ isn’t been interrupted correctly (it’s been consider as a literal and not expanded by the exec function)

For example, if I use something like.

 ProcessBuilder pb = new ProcessBuilder("ls", "~"); pb.redirectErrorStream(true); try < Process p = pb.start(); InputStream is = null; try < is = p.getInputStream(); int in = -1; while ((in = is.read()) >= 0) < System.out.print((char) in); >> finally < try < if (is != null) < is.close(); >> catch (Exception e) < >> System.out.println("Exited with " + p.waitFor()); > catch (IOException exp) < exp.printStackTrace(); >catch (InterruptedException exp)

ls: cannot access ~: No such file or directory Exited with 2 

ProcessBuilder pb = new ProcessBuilder("ls"); 

If you need the user home directory, then you’re going to need to interrupt it yourself, using System.getProperty(«user.home») , for example

ProcessBuilder pb = new ProcessBuilder("ls", System.getProperty("user.home")); 

I would also, highly, recommend the use of ProcessBuilder , it allows you to redirect the error stream to (among other places) the InputStream , which will make life a LOT easier and change the «working» directory from which the process is executed, it also handles arguments with spaces better, which means you could do something like.

ProcessBuilder pb = new ProcessBuilder("ls"); pb.directory(new File(System.getProperty("user.home"))); 

And get the same result as before

Further Testing.

Not having pdfgrep installed, I thought I might try grep

ProcessBuilder pb = new ProcessBuilder("grep", "-i", "banana", "~/Test.txt"); 

grep: ~/Test.txt: No such file or directory Exited with 2 

(and yes, Test.txt is in the home directory)

ProcessBuilder pb = new ProcessBuilder("grep", "-i", "banana", "Test.txt"); pb.directory(new File(System.getProperty("user.home"))); 

Bananas are yellow Exited with 0 

Java — Command Line Argument the File, I’m having a hard time changing the code to be a command line argument. Right now I’m still using a scanner to read in my text. I’m reading in and I need to read out as well. Like: public stati

Reading Java command line arguments on Unix

It’s not entirely clear what you’re trying to do.

If you want each filename under your folder as an argument to your command, try something like

. which will execute the ls command against ../folder and substitute the output (the list of files under ../folder).

Here is a simple program to list the files in a directory specified on the command line.

public static void main(String. argv) < File[] list = new File(argv[0]).listFiles(); for (File f : list) < System.out.println(f.getAbsolutePath()); >> 

The key question is «Does the Java application expect a directory name or a list of file names?»

If the application expects a directory name, you appear to have given it a directory name. Unless your shell script does something unexpected such as change working directory ( cd ), the problem is most likely in the application.

If the application expects a list of file names, then you should pass it file names and not a directory name. That might be just:

Or you might need to be more selective if the folder also contains sub-folders and the application will be upset by folder names instead of file names.

Command line — Passing a file as a Commandline, Passing a file as a Commandline argument in Java. I’m trying to write a program in Java to run pdfgrep in commandline on a given file, but I’m having trouble getting it to execute. public class PDFGrepCall < public static void main (String [] args) throws IOException, InterruptedException < PDFGrepCall obj = new …

Using files as command line args Java

You need to pass in the url of the files via command line and then create new files from the urls.

public static void main(String[] args) < File file1 = new File(args[0]); File file2 = new File(args[1]); 

You cannot pass files as command line arguments, you have to pass file names as command line arguments and open that file in main function

Assuming that you want to open the files, remember that File in Java is an object that stores path and name information. Once you have created the file objects, you can use them to construct a FileInputStream or one of its children.

Java - I want to read a file name from command line, Teams. Q&A for work. Connect and share knowledge within a single location that is structured and easy to search. Learn more about Teams

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Passing a file as a command line argument and reading its lines

You should do like this: Question: I have a question regarding to String[] args use in Java: That is just an example for file read, so if I want to run the code and put actual file name/path to the main() method, how can I achieve it, for instance, can I write it like : Solution 1: pass argument on command line like this where HelloWorld is java Class Name and hi java world are args for e.g: hi = args[0] , java = args[1] , hello = args[2] Solution 2: If you change yo varargs you can write Question: I'm having some trouble reading in a file from the command line.

Passing a file as a command line argument and reading its lines

this is the code that i have found in the internet for reading the lines of a file and also I use eclipse and I passed the name of files as SanShin.txt in its argument field. but it will print :

Error: textfile.txt (The system cannot find the file specified) 

public class Zip < public static void main(String[] args)< try< // Open the file that is the first // command line parameter FileInputStream fstream = new FileInputStream("textfile.txt"); BufferedReader br = new BufferedReader(new InputStreamReader(fstream)); String strLine; //Read File Line By Line while ((strLine = br.readLine()) != null) < // Print the content on the console System.out.println (strLine); >//Close the input stream in.close(); >catch (Exception e) > > 

please help me why it prints this error. thanks

. // command line parameter if(argv.length != 1) < System.err.println("Invalid command line, exactly one argument required"); System.exit(1); >try < FileInputStream fstream = new FileInputStream(argv[0]); >catch (FileNotFoundException e) < // TODO Auto-generated catch block e.printStackTrace(); >// Get the object of DataInputStream . > java -cp . Zip \path\to\test.file 

When you just specify "textfile.txt" the operating system will look in the program's working directory for that file.

You can specify the absolute path to the file with something like new FileInputStream("C:\\full\\path\\to\\file.txt")

Also if you want to know the directory your program is running in, try this: System.out.println(new File(".").getAbsolutePath())

Your new FileInputStream("textfile.txt") is correct. If it's throwing that exception, there is no textfile.txt in the current directory when you run the program. Are you sure the file's name isn't actually testfile.txt (note the s , not x , in the third position).

Off-topic : But your earlier deleted question asked how to read a file line by line (I didn't think you needed to delete it, FWIW). On the assumption you're still a beginner and getting the hang of things, a pointer: You probably don't want to be using FileInputStream , which is for binary files, but instead use the Reader set of interfaces/classes in java.io (including FileReader ). Also, whenever possible, declare your variables using the interface, even when initializing them to a specific class, so for instance, Reader r = new FileReader("textfile.txt") (rather than FileReader r = . ).

Reading in and Writing to files passed as commandline arguments, File input = ; // create the file so that it exists before writing output FileOutputStream outStream ; BufferedReader reader =

Beginner Java Tutorial: File IO, Reading From a Text File

This tutorial demonstrates how to read from a text file and how to pass arguments to java
Duration: 20:28

Reading from arguments files to process

I'm having some trouble reading in a file from the command line. I've never used command line arguments before so I guess I'm a little lost. Here's what I'm trying so far:

FileInputStream fin1 = null; for (int i = 0; i < args.length; i++) //command line argument for file input < fin1 = new FileInputStream(args[i]); >//Scanner scan = new Scanner(fiin1); 

I've commented out my scanner because I'm using a different method (into which I'm passing in fin1 as a parameter) and that method has a scanner in it. However, I'm not too sure if I still need the scanner there (maybe to pass into the other method as a param).

Anyway, if I run my code, I get a NullPointerException, which I assume comes from the fact that I initialized my fileinputstream as null. But if I'm changing it in the for loop, why does that matter? Also, I need to keep my main method the way it is so I can do more in it.

Notice that it is called File InputStream , and so we need to be using a File .

You can simply use a Scanner , and set it to System.in :

 Scanner scanner = new Scanner(System.in); 

And then afterwards, you can initialize that FileInputStream

How to Read Strings from Scanner in console Application JAVA?

 if (args.length < 1) < System.out.println("No file was given as an argument. "); System.exit(1); >String fileName = args[0]; Scanner scanner = new Scanner(new File(fileName)); 

if you want to use a FileInputStream then change the last line to create a FileInputStream instance.

 fin1 = new FileInputStream(fileName); 

No need to use a for-loop if you are giving only one filename as the argument. You can run your code as follow.

javac MyClass.java //Compile your code(Assumed that your file is MyClass.java java MyClass filename //Change filename with the path to your file 

You are getting NullPointerException probably because you are not using filename as a argument when you run your java code.

First of all : when you run your code, you'll reach only the last argument. You should do like this:

 FileInputStream fileInputStream = null; for (String argument : args) < fileInputStream = new FileInputStream(argument); //you should process your argument in block together with creating fis Scanner scanner = new Scanner(fileInputStream); //now, when a scanner copy is created, you can use it (or you can use your own while (scanner.hasNext()) < System.out.println(scanner.nextLine()); >> 

How to read from a txt file in eclipse commandline arguments but, // open output file for writing words******Code In Question**** try < //filewriter FileWriter fw = new FileWriter(file); wdWriter = new

Args [] for file read

I have a question regarding to String[] args use in Java:

 . public static void main(String[] args) throws Exception < new EMR().start(args); >public void start(String[] args) throws Exception < File recordFile = new File(args[0]); File instructionFile = new File(args[1]); File outputFile = new File(args[2]); . 

That is just an example for file read, so if I want to run the code and put actual file name/path to the main() method, how can I achieve it, for instance, can I write it like :

pass argument on command line like this

C:\myfolder> java HelloWorld hi java world 

where HelloWorld is java Class Name and hi java world are args for e.g: hi = args[0] , java = args[1] , hello = args[2]

If you change yo varargs you can write

new EMR().start("1.txt", "2.txt", "3.txt"); public void start(String. args) throws IOException  

new EMR().start("1.txt 2.txt 3.txt".split(" "));