C system() equivalent method. (original) (raw)

Frédéric Martini frederic.martini at gmail.com
Thu Oct 15 13:32:30 UTC 2009

Hello,

Sorry to revive this request, but I think this is as simple but very useful method that must be present on Java 7.

No one have an opinion on this?

Fred,

Le 17 septembre 2009 09:16, Frédéric Martini <frederic.martini at gmail.com> a écrit :

Hello (before to start, sorry for my bad english)

I have seen in the last JDK's build that ProcessBuilder allow to manage the process I/O more efficiently. In particular, the inheritIO() set the subprocess standard I/O to be the same as those of the current Java process, and offer a behavior "equivalent" to the standard C library function system(). This is very great an usefull ! But there is another BIG difference between ProcessBuilder and the C library function system() : ProcessBuilder execute an application, and C system() evaluate a command-line using the OS's shell. So C's system() can use a lot of OS's specific syntax ($ENV or %ENV%, * ?, pipe, redirect, etc...) witch is incorrect on a ProcessBuilder (because this syntax is not interpreted but directly passed to the application). This is a common misunderstanding for Java's developer... My proposal simply consist to add a method that create a ProcessBuilder pre-filled with a shell command's line, by invoking the OS's shell ("/bin/sh" on Unixes, "command.com" on Win9x, "cmd.exe" on WinNT, etc. ? ) in order to evaluate a more complex command-line. A "basic" implementation can be like this : ====================================================================== /** * Create a new ProcessBuilder initialized to call an OS's * specific command-line. */ public static ProcessBuilder createShellFor(String commandLine) { String osName = System.getProperty("os.name"); if (osName.startsWith("Windows")) { if (osName.startsWith("Windows 95") || osName.startsWith("Windows 98") || osName.startsWith("Windows Me") ) { return new ProcessBuilder("command.com", "/C", commandLine); } return new ProcessBuilder("cmd.exe", "/C", commandLine); } return new ProcessBuilder("/bin/sh", "-c", commandLine); } ====================================================================== This method can be improved with more specific code depending on OS.

And a "system()" method with a behavior really equivalent to the standard C library function system(), like this : ====================================================================== /** * Executes a command specified in 'commandLine' by calling * the OS shell program, and returns after the command has been completed. * @param commandLine The command-line to execute, using OS shell. * @return the exit value of the subprocess */ public static int system(String commandLine) throws IOException, InterruptedException { final Process process = createShellFor(commandLine).inheritIO().start(); try { return process.waitFor(); } finally { process.destroy(); } } ====================================================================== So, more complex and specific command-line can be used directly, like in lots of others languages... Thanks for reading, Fred -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.openjdk.java.net/pipermail/core-libs-dev/attachments/20091015/e26c5771/attachment.html>

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