ProcessBuilder.java revision 25
* system-dependent. For example, it is common for each conceptual * argument to be an element in this list, but there are operating * systems where programs are expected to tokenize command line * strings themselves - on such a system a Java implementation might * require commands to contain exactly two elements. * <li>an <i>environment</i>, which is a system-dependent mapping from * <i>variables</i> to <i>values</i>. The initial value is a copy of * the environment of the current process (see {@link System#getenv()}). * <li>a <i>working directory</i>. The default value is the current * working directory of the current process, usually the directory * named by the system property {@code user.dir}. * <li><a name="redirect-input">a source of <i>standard input</i>. * By default, the subprocess reads input from a pipe. Java code * can access this pipe via the output stream returned by * {@link Process#getOutputStream()}. However, standard input may * be redirected to another source using * {@link #redirectInput(Redirect) redirectInput}. * In this case, {@link Process#getOutputStream()} will return a * <i>null output stream</i>, for which: * <li>the {@link OutputStream#write(int) write} methods always * throw {@code IOException} * <li>the {@link OutputStream#close() close} method does nothing * <li><a name="redirect-output">a destination for <i>standard output</i> * and <i>standard error</i>. By default, the subprocess writes standard * output and standard error to pipes. Java code can access these pipes * via the input streams returned by {@link Process#getInputStream()} and * {@link Process#getErrorStream()}. However, standard output and * standard error may be redirected to other destinations using * {@link #redirectOutput(Redirect) redirectOutput} and * {@link #redirectError(Redirect) redirectError}. * In this case, {@link Process#getInputStream()} and/or * {@link Process#getErrorStream()} will return a <i>null input * <li>the {@link InputStream#read() read} methods always return * <li>the {@link InputStream#available() available} method always returns * <li>the {@link InputStream#close() close} method does nothing * <li>a <i>redirectErrorStream</i> property. Initially, this property * is {@code false}, meaning that the standard output and error * output of a subprocess are sent to two separate streams, which can * be accessed using the {@link Process#getInputStream()} and {@link * Process#getErrorStream()} methods. * <p>If the value is set to {@code true}, then: * <li>standard error is merged with the standard output and always sent * to the same destination (this makes it easier to correlate error * messages with the corresponding output) * <li>the common destination of standard error and standard output can be * {@link #redirectOutput(Redirect) redirectOutput} * <li>any redirection set by the * {@link #redirectError(Redirect) redirectError} * method is ignored when creating a subprocess * <li>the stream returned from {@link Process#getErrorStream()} will * always be a <a href="#redirect-output">null input stream</a> * <p>Modifying a process builder's attributes will affect processes * subsequently started by that object's {@link #start()} method, but * will never affect previously started processes or the Java process * <p>Most error checking is performed by the {@link #start()} method. * It is possible to modify the state of an object so that {@link * #start()} will fail. For example, setting the command attribute to * an empty list will not throw an exception unless {@link #start()} * <p><strong>Note that this class is not synchronized.</strong> * If multiple threads access a {@code ProcessBuilder} instance * concurrently, and at least one of the threads modifies one of the * attributes structurally, it <i>must</i> be synchronized externally. * <p>Starting a new process which uses the default working directory * and environment is easy: * Process p = new ProcessBuilder("myCommand", "myArg").start(); * <p>Here is an example that starts a process with a modified working * directory and environment, and redirects standard output and error * to be appended to a log file: * new ProcessBuilder("myCommand", "myArg1", "myArg2"); * Map<String, String> env = pb.environment(); * env.put("VAR1", "myValue"); * env.remove("OTHERVAR"); * env.put("VAR2", env.get("VAR1") + "suffix"); * pb.directory(new File("myDir")); * File log = new File("log"); * pb.redirectErrorStream(true); * pb.redirectOutput(Redirect.appendTo(log)); * Process p = pb.start(); * assert pb.redirectInput() == Redirect.PIPE; * assert pb.redirectOutput().file() == log; * assert p.getInputStream().read() == -1; * <p>To start a process with an explicit set of environment * variables, first call {@link java.util.Map#clear() Map.clear()} * before adding environment variables. * @author Martin Buchholz * Constructs a process builder with the specified operating * system program and arguments. This constructor does <i>not</i> * make a copy of the {@code command} list. Subsequent * updates to the list will be reflected in the state of the * process builder. It is not checked whether * {@code command} corresponds to a valid operating system * @param command the list containing the program and its arguments * @throws NullPointerException if the argument is null * Constructs a process builder with the specified operating * system program and arguments. This is a convenience * constructor that sets the process builder's command to a string * list containing the same strings as the {@code command} * array, in the same order. It is not checked whether * {@code command} corresponds to a valid operating system * @param command a string array containing the program and its arguments * Sets this process builder's operating system program and * arguments. This method does <i>not</i> make a copy of the * {@code command} list. Subsequent updates to the list will * be reflected in the state of the process builder. It is not * checked whether {@code command} corresponds to a valid * operating system command. * @param command the list containing the program and its arguments * @return this process builder * @throws NullPointerException if the argument is null * Sets this process builder's operating system program and * arguments. This is a convenience method that sets the command * to a string list containing the same strings as the * {@code command} array, in the same order. It is not * checked whether {@code command} corresponds to a valid * operating system command. * @param command a string array containing the program and its arguments * @return this process builder * Returns this process builder's operating system program and * arguments. The returned list is <i>not</i> a copy. Subsequent * updates to the list will be reflected in the state of this * @return this process builder's program and its arguments * Returns a string map view of this process builder's environment. * Whenever a process builder is created, the environment is * initialized to a copy of the current process environment (see * {@link System#getenv()}). Subprocesses subsequently started by * this object's {@link #start()} method will use this map as * <p>The returned object may be modified using ordinary {@link * java.util.Map Map} operations. These modifications will be * visible to subprocesses started via the {@link #start()} * method. Two {@code ProcessBuilder} instances always * contain independent process environments, so changes to the * returned map will never be reflected in any other * {@code ProcessBuilder} instance or the values returned by * {@link System#getenv System.getenv}. * <p>If the system does not support environment variables, an * <p>The returned map does not permit null keys or values. * Attempting to insert or query the presence of a null key or * value will throw a {@link NullPointerException}. * Attempting to query the presence of a key or value which is not * of type {@link String} will throw a {@link ClassCastException}. * <p>The behavior of the returned map is system-dependent. A * system may not allow modifications to environment variables or * may forbid certain variable names or values. For this reason, * attempts to modify the map may fail with * {@link UnsupportedOperationException} or * {@link IllegalArgumentException} * if the modification is not permitted by the operating system. * <p>Since the external format of environment variable names and * values is system-dependent, there may not be a one-to-one * mapping between them and Java's Unicode strings. Nevertheless, * the map is implemented in such a way that environment variables * which are not modified by Java code will have an unmodified * native representation in the subprocess. * <p>The returned map and its collection views may not obey the * general contract of the {@link Object#equals} and * {@link Object#hashCode} methods. * <p>The returned map is typically case-sensitive on all platforms. * <p>If a security manager exists, its * {@link SecurityManager#checkPermission checkPermission} method * {@link RuntimePermission}{@code ("getenv.*")} permission. * This may result in a {@link SecurityException} being thrown. * <p>When passing information to a Java subprocess, * <a href=System.html#EnvironmentVSSystemProperties>system properties</a> * are generally preferred over environment variables. * @return this process builder's environment * @throws SecurityException * if a security manager exists and its * {@link SecurityManager#checkPermission checkPermission} * method doesn't allow access to the process environment * @see Runtime#exec(String[],String[],java.io.File) // Only for use by Runtime.exec(...envp...) // Before 1.5, we blindly passed invalid envstrings // We would like to throw an exception, but do not, // for compatibility with old broken code. // Silently discard any trailing junk. // Silently ignore envstrings lacking the required `='. * Returns this process builder's working directory. * Subprocesses subsequently started by this object's {@link * #start()} method will use this as their working directory. * The returned value may be {@code null} -- this means to use * the working directory of the current Java process, usually the * directory named by the system property {@code user.dir}, * as the working directory of the child process. * @return this process builder's working directory * Sets this process builder's working directory. * Subprocesses subsequently started by this object's {@link * #start()} method will use this as their working directory. * The argument may be {@code null} -- this means to use the * working directory of the current Java process, usually the * directory named by the system property {@code user.dir}, * as the working directory of the child process. * @param directory the new working directory * @return this process builder // ---------------- I/O Redirection ---------------- * Implements a <a href="#redirect-output">null input stream</a>. public int read() {
return -
1; }
* Implements a <a href="#redirect-input">null output stream</a>. * Represents a source of subprocess input or a destination of * Each {@code Redirect} instance is one of the following: * <li>the special value {@link #PIPE Redirect.PIPE} * <li>the special value {@link #INHERIT Redirect.INHERIT} * <li>a redirection to read from a file, created by an invocation of * {@link Redirect#from Redirect.from(File)} * <li>a redirection to write to a file, created by an invocation of * {@link Redirect#to Redirect.to(File)} * <li>a redirection to append to a file, created by an invocation of * {@link Redirect#appendTo Redirect.appendTo(File)} * <p>Each of the above categories has an associated unique * The type of a {@link Redirect}. * The type of {@link Redirect#PIPE Redirect.PIPE}. * The type of {@link Redirect#INHERIT Redirect.INHERIT}. * The type of redirects returned from * {@link Redirect#from Redirect.from(File)}. * The type of redirects returned from * {@link Redirect#to Redirect.to(File)}. * The type of redirects returned from * {@link Redirect#appendTo Redirect.appendTo(File)}. * Returns the type of this {@code Redirect}. * @return the type of this {@code Redirect} * Indicates that subprocess I/O will be connected to the * current Java process over a pipe. * This is the default handling of subprocess standard I/O. * <p>It will always be true that * Redirect.PIPE.file() == null && * Redirect.PIPE.type() == Redirect.Type.PIPE * Indicates that subprocess I/O source or destination will be the * same as those of the current process. This is the normal * behavior of most operating system command interpreters (shells). * <p>It will always be true that * Redirect.INHERIT.file() == null && * Redirect.INHERIT.type() == Redirect.Type.INHERIT * Returns the {@link File} source or destination associated * with this redirect, or {@code null} if there is no such file. * @return the file associated with this redirect, * or {@code null} if there is no such file * Returns a redirect to read from the specified file. * <p>It will always be true that * Redirect.from(file).file() == file && * Redirect.from(file).type() == Redirect.Type.READ * @throws NullPointerException if the specified file is null * @return a redirect to read from the specified file return "redirect to read from file \"" +
file +
"\"";
* Returns a redirect to write to the specified file. * If the specified file exists when the subprocess is started, * its previous contents will be discarded. * <p>It will always be true that * Redirect.to(file).file() == file && * Redirect.to(file).type() == Redirect.Type.WRITE * @throws NullPointerException if the specified file is null * @return a redirect to write to the specified file return "redirect to write to file \"" +
file +
"\"";
* Returns a redirect to append to the specified file. * Each write operation first advances the position to the * end of the file and then writes the requested data. * Whether the advancement of the position and the writing * of the data are done in a single atomic operation is * system-dependent and therefore unspecified. * <p>It will always be true that * Redirect.appendTo(file).file() == file && * Redirect.appendTo(file).type() == Redirect.Type.APPEND * @throws NullPointerException if the specified file is null * @return a redirect to append to the specified file return "redirect to append to file \"" +
file +
"\"";
* Compares the specified object with this {@code Redirect} for * equality. Returns {@code true} if and only if the two * objects are identical or both objects are {@code Redirect} * instances of the same type associated with non-null equal * {@code File} instances. * Returns a hash code value for this {@code Redirect}. * @return a hash code value for this {@code Redirect} * No public constructors. Clients must use predefined * static {@code Redirect} instances or factory methods. * Sets this process builder's standard input source. * Subprocesses subsequently started by this object's {@link #start()} * method obtain their standard input from this source. * <p>If the source is {@link Redirect#PIPE Redirect.PIPE} * (the initial value), then the standard input of a * subprocess can be written to using the output stream * returned by {@link Process#getOutputStream()}. * If the source is set to any other value, then * {@link Process#getOutputStream()} will return a * <a href="#redirect-input">null output stream</a>. * @param source the new standard input source * @return this process builder * @throws IllegalArgumentException * if the redirect does not correspond to a valid source * of data, that is, has type * {@link Redirect.Type#WRITE WRITE} or * {@link Redirect.Type#APPEND APPEND} "Redirect invalid for reading: " +
source);
* Sets this process builder's standard output destination. * Subprocesses subsequently started by this object's {@link #start()} * method send their standard output to this destination. * <p>If the destination is {@link Redirect#PIPE Redirect.PIPE} * (the initial value), then the standard output of a subprocess * can be read using the input stream returned by {@link * Process#getInputStream()}. * If the destination is set to any other value, then * {@link Process#getInputStream()} will return a * <a href="#redirect-output">null input stream</a>. * @param destination the new standard output destination * @return this process builder * @throws IllegalArgumentException * if the redirect does not correspond to a valid * destination of data, that is, has type * {@link Redirect.Type#READ READ} * Sets this process builder's standard error destination. * Subprocesses subsequently started by this object's {@link #start()} * method send their standard error to this destination. * <p>If the destination is {@link Redirect#PIPE Redirect.PIPE} * (the initial value), then the error output of a subprocess * can be read using the input stream returned by {@link * Process#getErrorStream()}. * If the destination is set to any other value, then * {@link Process#getErrorStream()} will return a * <a href="#redirect-output">null input stream</a>. * <p>If the {@link #redirectErrorStream redirectErrorStream} * attribute has been set {@code true}, then the redirection set * by this method has no effect. * @param destination the new standard error destination * @return this process builder * @throws IllegalArgumentException * if the redirect does not correspond to a valid * destination of data, that is, has type * {@link Redirect.Type#READ READ} * Sets this process builder's standard input source to a file. * <p>This is a convenience method. An invocation of the form * {@code redirectInput(file)} * behaves in exactly the same way as the invocation * {@link #redirectInput(Redirect) redirectInput} * {@code (Redirect.from(file))}. * @param file the new standard input source * @return this process builder * Sets this process builder's standard output destination to a file. * <p>This is a convenience method. An invocation of the form * {@code redirectOutput(file)} * behaves in exactly the same way as the invocation * {@link #redirectOutput(Redirect) redirectOutput} * {@code (Redirect.to(file))}. * @param file the new standard output destination * @return this process builder * Sets this process builder's standard error destination to a file. * <p>This is a convenience method. An invocation of the form * {@code redirectError(file)} * behaves in exactly the same way as the invocation * {@link #redirectError(Redirect) redirectError} * {@code (Redirect.to(file))}. * @param file the new standard error destination * @return this process builder * Returns this process builder's standard input source. * Subprocesses subsequently started by this object's {@link #start()} * method obtain their standard input from this source. * The initial value is {@link Redirect#PIPE Redirect.PIPE}. * @return this process builder's standard input source * Returns this process builder's standard output destination. * Subprocesses subsequently started by this object's {@link #start()} * method redirect their standard output to this destination. * The initial value is {@link Redirect#PIPE Redirect.PIPE}. * @return this process builder's standard output destination * Returns this process builder's standard error destination. * Subprocesses subsequently started by this object's {@link #start()} * method redirect their standard error to this destination. * The initial value is {@link Redirect#PIPE Redirect.PIPE}. * @return this process builder's standard error destination * Sets the source and destination for subprocess standard I/O * to be the same as those of the current Java process. * <p>This is a convenience method. An invocation of the form * behaves in exactly the same way as the invocation * pb.redirectInput(Redirect.INHERIT) * .redirectOutput(Redirect.INHERIT) * .redirectError(Redirect.INHERIT) * This gives behavior equivalent to most operating system * command interpreters, or the standard C library function * @return this process builder * Tells whether this process builder merges standard error and * <p>If this property is {@code true}, then any error output * generated by subprocesses subsequently started by this object's * {@link #start()} method will be merged with the standard * output, so that both can be read using the * {@link Process#getInputStream()} method. This makes it easier * to correlate error messages with the corresponding output. * The initial value is {@code false}. * @return this process builder's {@code redirectErrorStream} property * Sets this process builder's {@code redirectErrorStream} property. * <p>If this property is {@code true}, then any error output * generated by subprocesses subsequently started by this object's * {@link #start()} method will be merged with the standard * output, so that both can be read using the * {@link Process#getInputStream()} method. This makes it easier * to correlate error messages with the corresponding output. * The initial value is {@code false}. * @param redirectErrorStream the new property value * @return this process builder * Starts a new process using the attributes of this process builder. * <p>The new process will * invoke the command and arguments given by {@link #command()}, * in a working directory as given by {@link #directory()}, * with a process environment as given by {@link #environment()}. * <p>This method checks that the command is a valid operating * system command. Which commands are valid is system-dependent, * but at the very least the command must be a non-empty list of * <p>If there is a security manager, its * {@link SecurityManager#checkExec checkExec} * method is called with the first component of this object's * {@code command} array as its argument. This may result in * a {@link SecurityException} being thrown. * <p>Starting an operating system process is highly system-dependent. * Among the many things that can go wrong are: * <li>The operating system program file was not found. * <li>Access to the program file was denied. * <li>The working directory does not exist. * <p>In such cases an exception will be thrown. The exact nature * of the exception is system-dependent, but it will always be a * subclass of {@link IOException}. * <p>Subsequent modifications to this process builder will not * affect the returned {@link Process}. * @return a new {@link Process} object for managing the subprocess * @throws NullPointerException * if an element of the command list is null * @throws IndexOutOfBoundsException * if the command is an empty list (has size {@code 0}) * @throws SecurityException * if a security manager exists and * {@link SecurityManager#checkExec checkExec} * method doesn't allow creation of the subprocess, or * <li>the standard input to the subprocess was * {@linkplain #redirectInput redirected from a file} * and the security manager's * {@link SecurityManager#checkRead checkRead} method * denies read access to the file, or * <li>the standard output or standard error of the * {@linkplain #redirectOutput redirected to a file} * and the security manager's * {@link SecurityManager#checkWrite checkWrite} method * denies write access to the file * @throws IOException if an I/O error occurs * @see Runtime#exec(String[], String[], java.io.File) // Must convert to array first -- a malicious user-supplied // list might try to circumvent the security check. // Throws IndexOutOfBoundsException if command is empty // It's much easier for us to create a high-quality error // message than the low-level C code which found the problem. "Cannot run program \"" +
prog +
"\"" + (
dir ==
null ?
"" :
" (in directory \"" +
dir +
"\")")