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import java.io.*; // This appears in Core Web Programming from // Prentice Hall Publishers, and may be freely used // or adapted. 1997 Marty Hall, [email protected]. /** A class that eases the pain of running external * processes from applications. * Lets you run a program three ways: * <OL> * <LI><B>exec</B>: Execute the command, returning * immediately even if the command is still * running. This would be appropriate * for printing a file. * <LI><B>execWait</B>: Execute the command, but * don't return until the command finishes. * This would be appropriate for * sequential commands where the first depends * on the second having finished (e.g. * <CODE>javac</CODE> followed by * <CODE>java</CODE>). * <LI><B>execPrint</B>: Execute the command and * print the output. This would be appropriate * for the UNIX command <CODE>ls</CODE>. * </OL> * Note that the PATH is not taken into account, * so you must specify the <B>full</B> pathname to * the command, and shell builtin commands * will not work. For instance, on Unix the above * three examples might look like: * <OL> * <LI><PRE>Exec.exec("/usr/ucb/lpr Some-File");</PRE> * <LI><PRE> * Exec.execWait("/usr/local/bin/javac Foo.java"); * Exec.execWait("/usr/local/bin/java Foo"); * </PRE> * <LI><PRE>Exec.execPrint("/usr/bin/ls -al");</PRE> * </OL> * * @author Marty Hall * (<A HREF="mailto:[email protected]"> * [email protected]</A>) * @version 1.0 1997 */ public class Exec { //---------------------------------------------------- private static boolean verbose = true; /** Determines if the Exec class should print which * commands are being executed, and print error * messages if a problem is found. Default is true. * * @param verboseFlag true: print messages. * false: don't. */ public static void setVerbose(boolean verboseFlag) { verbose = verboseFlag; } /** Will Exec print status messages? */ public static boolean getVerbose() { return(verbose); } //---------------------------------------------------- /** Starts a process to execute the command. Returns * immediately, even if the new process is still * running. * * @param command The <B>full</B> pathname of the * command to be executed. No shell builtins * (e.g. "cd") or shell meta-chars (e.g. ">") * allowed. * @return false if a problem is known to occur, but * since this returns immediately, problems * aren't usually found in time. * Returns true otherwise. */ public static boolean exec(String command) { return(exec(command, false, false)); } //---------------------------------------------------- /** Starts a process to execute the command. Waits * for the process to finish before returning. * * @param command The <B>full</B> pathname of the * command to be executed. No shell builtins * or shell meta-chars allowed. * @return false if a problem is known to occur, * either due to an exception or from the * subprocess returning a non-zero value. * Returns true otherwise. */ public static boolean execWait(String command) { return(exec(command, false, true)); } //---------------------------------------------------- /** Starts a process to execute the command. Prints * all output the command gives. * * @param command The <B>full</B> pathname of the * command to be executed. No shell builtins * or shell meta-chars allowed. * @return false if a problem is known to occur, * either due to an exception or from the * subprocess returning a non-zero value. * Returns true otherwise. */ public static boolean execPrint(String command) { return(exec(command, true, false)); } //---------------------------------------------------- // This creates a Process object via // Runtime.getRuntime.exec(). Depending on the // flags, it may call waitFor on the process // to avoid continuing until the process terminates, // or open an input stream from the process to read // the results. private static boolean exec(String command, boolean printResults, boolean wait) { if (verbose) { printSeparator(); System.out.println("Executing '" + command + "'."); } try { // Start running command, returning immediately. Process p = Runtime.getRuntime().exec(command); // Print the output. Since we read until // there is no more input, this causes us // to wait until the process is completed if(printResults) { BufferedInputStream buffer = new BufferedInputStream(p.getInputStream()); DataInputStream commandResult = new DataInputStream(buffer); String s = null; try { while ((s = commandResult.readLine()) != null) System.out.println("Output: " + s); commandResult.close(); if (p.exitValue() != 0) { if (verbose) printError(command + " -- p.exitValue() != 0"); return(false); } // Ignore read errors; they mean process is done } catch (Exception e) {} // If you don't print the results, then you // need to call waitFor to stop until the process // is completed } else if (wait) { try { System.out.println(" "); int returnVal = p.waitFor(); if (returnVal != 0) { if (verbose) printError(command); return(false); } } catch (Exception e) { if (verbose) printError(command, e); return(false); } } } catch (Exception e) { if (verbose) printError(command, e); return(false); } return(true); } //---------------------------------------------------- private static void printError(String command, Exception e) { System.out.println("Error doing exec(" + command + "): " + e.getMessage()); System.out.println("Did you specify the full " + "pathname?"); } private static void printError(String command) { System.out.println("Error executing '" + command + "'."); } //---------------------------------------------------- private static void printSeparator() { System.out.println ("=============================================="); } //---------------------------------------------------- }