Can I find the console width with Java?

masher_36061 0
Viewed 32245

Is there a way to find the width of the console in which my Java program is running?

I would like this to be cross platform if possible...

I have no desire to change the width of the buffer or the window, I just want to know its width so I can properly format text that is being printed to screen.

console java
8 Answers

There's a trick that you can use based on ANSI Escape Codes. They don't provide a direct way to query the console size, but they do have a command for requesting the current cursor position. By moving the cursor to a really high row and column and then requesting the cursor position you can get an accurate measurement.

Combine this with commands to store/restore the cursor position, as in the following example:

Send the following sequences to the terminal (stdout)

"\u001b[s"             // save cursor position
"\u001b[5000;5000H"    // move to col 5000 row 5000
"\u001b[6n"            // request cursor position
"\u001b[u"             // restore cursor position

Now watch stdin, you should receive a sequece that looks like \u001b[25;80R", where 25 is the row count, and 80 the columns.

I first saw this used in the Lanterna library.

Update:

There are really four different ways that I know of to achieve this, but they all make certain assumptions about the environment the program is running in, or the terminal device/emulator it is talking to.

  • Using the VT100 protocol. This is what this solution does, it assumes you are talking over stdin/stdout to a terminal emulator that honors these escape codes. This seems like a relatively safe assumption for a CLI program, but e.g. if someone is using cmd.exe this likely won't work.
  • terminfo/termcap. These are databases with terminal information, which you can query for instance with tput. Operating system dependent, and assumes you are connected to a TTY device. Won't work over ssh for instance.
  • Using the telnet protocol. Telnet has its own affordances for querying the screen size, but of course this only works if people connect to your application via the telnet client, not really an option in most cases.
  • Rely on the shell (e.g. bash), this is what solutions that use COLUMNS/ROWS variables do. Far from universal, but could work quite well if you provide a wrapper script for your app that makes sure the necessary env vars are exported.
user_18914480
Related