Index: src/OFProcess.h
==================================================================
--- src/OFProcess.h
+++ src/OFProcess.h
@@ -27,10 +27,14 @@
 
 #ifdef _WIN32
 # include <windows.h>
 #endif
 
+@class OFString;
+@class OFArray;
+@class OFDictionary;
+
 /*!
  * @brief A class for stream-like communication with a newly created process.
  */
 @interface OFProcess: OFStream
 {
@@ -79,10 +83,31 @@
  */
 + (instancetype)processWithProgram: (OFString*)program
 		       programName: (OFString*)programName
 			 arguments: (OFArray*)arguments;
 
+/*!
+ * @brief Creates a new OFProcess with the specified program, program name,
+ *	  arguments and environment and invokes the program.
+ *
+ * @param program The program to execute. If it does not start with a slash, the
+ *		  search path specified in PATH is used.
+ * @param programName The program name for the program to invoke (argv[0]).
+ *		      Usually, this is equal to program.
+ * @param arguments The arguments to pass to the program, or nil
+ * @param environment The environment to pass to the program, or nil. If it is
+ *		      non-nil, the passed dictionary will be used to override
+ *		      the environment. If you want to add to the existing
+ *		      environment, you need to get the existing environment
+ *		      first, copy it, modify it and then pass it.
+ * @return A new, autoreleased OFProcess.
+ */
++ (instancetype)processWithProgram: (OFString*)program
+		       programName: (OFString*)programName
+			 arguments: (OFArray*)arguments
+		       environment: (OFDictionary*)environment;
+
 /*!
  * @brief Initializes an already allocated OFProcess with the specified program
  *	  and invokes the program.
  *
  * @param program The program to execute. If it does not start with a slash, the
@@ -116,14 +141,37 @@
  */
 - initWithProgram: (OFString*)program
       programName: (OFString*)programName
 	arguments: (OFArray*)arguments;
 
+/*!
+ * @brief Initializes an already allocated OFProcess with the specified program,
+ *	  program name, arguments and environment and invokes the program.
+ *
+ * @param program The program to execute. If it does not start with a slash, the
+ *		  search path specified in PATH is used.
+ * @param programName The program name for the program to invoke (argv[0]).
+ *		      Usually, this is equal to program.
+ * @param arguments The arguments to pass to the program, or nil
+ * @param environment The environment to pass to the program, or nil. If it is
+ *		      non-nil, the passed dictionary will be used to override
+ *		      the environment. If you want to add to the existing
+ *		      environment, you need to get the existing environment
+ *		      first, copy it, modify it and then pass it.
+ * @return An initialized OFProcess.
+ */
+- initWithProgram: (OFString*)program
+      programName: (OFString*)programName
+	arguments: (OFArray*)arguments
+      environment: (OFDictionary*)environment;
+
+- (void)OF_setEnvironment: (OFDictionary*)dictionary;
+
 /*!
  * @brief Closes the write direction of the process.
  *
  * This method needs to be called for some programs before data can be read,
  * since some programs don't start processing before the write direction is
  * closed.
  */
 - (void)closeForWriting;
 @end

Index: src/OFProcess.m
==================================================================
--- src/OFProcess.m
+++ src/OFProcess.m
@@ -15,19 +15,25 @@
  */
 
 #include "config.h"
 
 #include <stdlib.h>
+#include <string.h>
 
 #ifndef _WIN32
 # include <unistd.h>
 # include <sys/wait.h>
 #endif
+
+#ifdef __MACH__
+# include <crt_externs.h>
+#endif
 
 #import "OFProcess.h"
 #import "OFString.h"
 #import "OFArray.h"
+#import "OFDictionary.h"
 
 #import "OFInitializationFailedException.h"
 #import "OFReadFailedException.h"
 #import "OFWriteFailedException.h"
 
@@ -34,10 +40,14 @@
 #ifdef _WIN32
 # include <windows.h>
 #endif
 
 #import "autorelease.h"
+
+#ifndef __MACH__
+extern char **environ;
+#endif
 
 @implementation OFProcess
 + (instancetype)processWithProgram: (OFString*)program
 {
 	return [[[self alloc] initWithProgram: program] autorelease];
@@ -56,29 +66,53 @@
 {
 	return [[[self alloc] initWithProgram: program
 				  programName: programName
 				    arguments: arguments] autorelease];
 }
+
++ (instancetype)processWithProgram: (OFString*)program
+		       programName: (OFString*)programName
+			 arguments: (OFArray*)arguments
+		       environment: (OFDictionary*)environment
+{
+	return [[[self alloc] initWithProgram: program
+				  programName: programName
+				    arguments: arguments
+				  environment: environment] autorelease];
+}
+
+- initWithProgram: (OFString*)program
+{
+	return [self initWithProgram: program
+			 programName: program
+			   arguments: nil
+			 environment: nil];
+}
 
 - initWithProgram: (OFString*)program
+	arguments: (OFArray*)arguments
 {
 	return [self initWithProgram: program
 			 programName: program
-			   arguments: nil];
+			   arguments: arguments
+			 environment: nil];
 }
 
 - initWithProgram: (OFString*)program
+      programName: (OFString*)programName
 	arguments: (OFArray*)arguments
 {
 	return [self initWithProgram: program
 			 programName: program
-			   arguments: arguments];
+			   arguments: arguments
+			 environment: nil];
 }
 
 - initWithProgram: (OFString*)program
       programName: (OFString*)programName
 	arguments: (OFArray*)arguments
+      environment: (OFDictionary*)environment
 {
 	self = [super init];
 
 	@try {
 #ifndef _WIN32
@@ -103,10 +137,13 @@
 				    cStringUsingEncoding:
 				    OF_STRING_ENCODING_NATIVE];
 
 			argv[i + 1] = NULL;
 
+			if (environment != nil)
+				[self OF_setEnvironment: environment];
+
 			close(readPipe[0]);
 			close(writePipe[1]);
 			dup2(writePipe[0], 0);
 			dup2(readPipe[1], 1);
 			execvp([program cStringUsingEncoding:
@@ -222,10 +259,55 @@
 		@throw e;
 	}
 
 	return self;
 }
+
+- (void)OF_setEnvironment: (OFDictionary*)environment
+{
+	OFEnumerator *keyEnumerator, *objectEnumerator;
+	char **envp;
+	size_t i, count;
+
+	count = [environment count];
+	envp = [self allocMemoryWithSize: sizeof(char*)
+				   count: count + 1];
+
+	keyEnumerator = [environment keyEnumerator];
+	objectEnumerator = [environment objectEnumerator];
+
+	for (i = 0; i < count; i++) {
+		OFString *key;
+		OFString *object;
+		size_t keyLen, objectLen;
+
+		key = [keyEnumerator nextObject];
+		object = [objectEnumerator nextObject];
+
+		keyLen = [key lengthOfBytesUsingEncoding:
+		    OF_STRING_ENCODING_NATIVE];
+		objectLen = [object lengthOfBytesUsingEncoding:
+		    OF_STRING_ENCODING_NATIVE];
+
+		envp[i] = [self allocMemoryWithSize: keyLen + objectLen + 2];
+
+		memcpy(envp[i], [key cStringUsingEncoding:
+		    OF_STRING_ENCODING_NATIVE], keyLen);
+		envp[i][keyLen] = '=';
+		memcpy(envp[i] + keyLen + 1, [object cStringUsingEncoding:
+		    OF_STRING_ENCODING_NATIVE], objectLen);
+		envp[i][keyLen + objectLen + 1] = '\0';
+	}
+
+	envp[i] = NULL;
+
+#ifdef __MACH__
+	*_NSGetEnviron() = envp;
+#else
+	environ = envp;
+#endif
+}
 
 - (BOOL)lowlevelIsAtEndOfStream
 {
 #ifndef _WIN32
 	if (readPipe[0] == -1)