Pass input to an application not reading from stdin

Question

I have an application that reads a text file.

If the application reads it from stdin, then I could forward the input / pipe it

$ app < input.txt
$ cat input.txt | app

Unfortunately, the application expects a filename as an argument..

$ app --input input.txt

and I can't easily change the source of input (eg. swap local file [as in example] for a result of a wget).

Is there an option to somehow trick this app?

If a solution requires a temporary file, it is necessary that this file is not left on the FS..

_{The app is actually an executable JAR; I'd like the trick to run on Win/Lin..}

mki · Accepted Answer · 2013-04-23 06:45:19Z

3

I am not sure if it could work for you, but I have already solve a similar problem with a fifo. http://linux.die.net/man/3/mkfifo

This could give you the indirection between your app and your source.

mkfifo fifo.input
app --input fifo.input

Now you can fill the pipe with different sources.

cat input > fifo.input
ctrl-c
cat otherInput > fifo.unput

Hope it solve your problem on Linux. So far I know it does not exist on Windows.

edited Apr 23, 2013 at 6:45

answered Apr 22, 2013 at 18:00

mki

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4 Comments

Roay Spol Over a year ago

this is very nice! Will the fifo.input disappear after reading by app?

mki Over a year ago

No but it take 0 space, the kernel redirect the output to the process directly, no disk space is used. The name on the disk is only an entry point.

Roay Spol Over a year ago

this is very good, if you can pinpoint a way to automatically dispose of whatever is created during this operation (even the hd entry), I can accept right away.

mki Over a year ago

If you can launch all your operations in a script it is simple, just remove the fifo at the end of the script : rm fifo.input

rahul maindargi · Accepted Answer · 2013-04-22 16:59:08Z

0

You want to do something like this.

 java -jar myjar.jar arg1 arg2

where myjar.jar is the executable jar and arg1 arg2 etc are parameters the program expects.

So suppose you want to pass input.txt to your application and its the only commandline parameter required then command will be

java -jar myjar.jar input.txt

answered Apr 22, 2013 at 16:59

rahul maindargi

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4 Comments

Deepak Bala Over a year ago

How exactly does this read from stdin !? This does not answer the OP's question.

rahul maindargi Over a year ago

The OP's want to change the source of input without creating the file at defualt location with defualt name. if the application uses sdin as input then he had thought of solution as frowarding the input or pipeing. but as he mentions its a executable jar and he was looking for giving the input without creating extra/temp file.

Roay Spol Over a year ago

suppose I don't want to pass an existing file (input.txt), but an online resource (like a webpage's html)

rahul maindargi Over a year ago

@RoaySpol have you tried creating script with wget to get html save it as temp file pass it to App as commandline parameter and then delete temp generaed file. a small .sh Linux or .bat windows should serve the perpose.

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