diff --git a/Makefile b/Makefile
index 86771a0..a630b93 100644
--- a/Makefile
+++ b/Makefile
@@ -7,7 +7,8 @@ SRCS	= picoc.c table.c lex.c parse.c expression.c heap.c type.c \
 	variable.c clibrary.c platform.c include.c \
 	platform/platform_unix.c platform/library_unix.c \
 	cstdlib/stdio.c cstdlib/math.c cstdlib/string.c cstdlib/stdlib.c \
-	cstdlib/time.c cstdlib/errno.c cstdlib/ctype.c cstdlib/stdbool.c
+	cstdlib/time.c cstdlib/errno.c cstdlib/ctype.c cstdlib/stdbool.c \
+	cstdlib/unistd.c
 OBJS	:= $(SRCS:%.c=%.o)
 
 all: depend $(TARGET)
diff --git a/cstdlib/unistd.c b/cstdlib/unistd.c
new file mode 100644
index 0000000..7a076f5
--- /dev/null
+++ b/cstdlib/unistd.c
@@ -0,0 +1,504 @@
+/* stdlib.h library for large systems - small embedded systems use clibrary.c instead */
+#include <stdio.h>
+#include <unistd.h>
+#include <limits.h>
+#include "../picoc.h"
+
+#ifndef BUILTIN_MINI_STDLIB
+
+static int ZeroValue = 0;
+
+void UnistdAccess(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = access(Param[0]->Val->Pointer, Param[1]->Val->Integer);
+}
+
+void UnistdAlarm(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = alarm(Param[0]->Val->Integer);
+}
+
+void UnistdBrk(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = brk(Param[0]->Val->Pointer);
+}
+
+void UnistdChdir(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = chdir(Param[0]->Val->Pointer);
+}
+
+void UnistdChroot(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = chroot(Param[0]->Val->Pointer);
+}
+
+void UnistdChown(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = chown(Param[0]->Val->Pointer, Param[1]->Val->Integer, Param[2]->Val->Integer);
+}
+
+void UnistdClose(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = close(Param[0]->Val->Integer);
+}
+
+void UnistdConfstr(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = confstr(Param[0]->Val->Integer, Param[1]->Val->Pointer, Param[2]->Val->Integer);
+}
+
+void UnistdCtermid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Pointer = ctermid(Param[0]->Val->Pointer);
+}
+
+#if 0
+void UnistdCuserid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Pointer = cuserid(Param[0]->Val->Pointer);
+}
+#endif
+
+void UnistdDup(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = dup(Param[0]->Val->Integer);
+}
+
+void UnistdDup2(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = dup2(Param[0]->Val->Integer, Param[1]->Val->Integer);
+}
+
+void Unistd_Exit(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    _exit(Param[0]->Val->Integer);
+}
+
+void UnistdFchown(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = fchown(Param[0]->Val->Integer, Param[1]->Val->Integer, Param[2]->Val->Integer);
+}
+
+void UnistdFchdir(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = fchdir(Param[0]->Val->Integer);
+}
+
+void UnistdFdatasync(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = fdatasync(Param[0]->Val->Integer);
+}
+
+void UnistdFork(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = fork();
+}
+
+void UnistdFpathconf(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = fpathconf(Param[0]->Val->Integer, Param[1]->Val->Integer);
+}
+
+void UnistdFsync(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = fsync(Param[0]->Val->Integer);
+}
+
+void UnistdFtruncate(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = ftruncate(Param[0]->Val->Integer, Param[1]->Val->Integer);
+}
+
+void UnistdGetcwd(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Pointer = getcwd(Param[0]->Val->Pointer, Param[1]->Val->Integer);
+}
+
+void UnistdGetdtablesize(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = getdtablesize();
+}
+
+void UnistdGetegid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = getegid();
+}
+
+void UnistdGeteuid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = geteuid();
+}
+
+void UnistdGetgid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = getgid();
+}
+
+void UnistdGethostid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = gethostid();
+}
+
+void UnistdGetlogin(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Pointer = getlogin();
+}
+
+void UnistdGetlogin_r(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = getlogin_r(Param[0]->Val->Pointer, Param[1]->Val->Integer);
+}
+
+void UnistdGetpagesize(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = getpagesize();
+}
+
+void UnistdGetpass(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Pointer = getpass(Param[0]->Val->Pointer);
+}
+
+#if 0
+void UnistdGetpgid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = getpgid(Param[0]->Val->Integer);
+}
+#endif
+
+void UnistdGetpgrp(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = getpgrp();
+}
+
+void UnistdGetpid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = getpid();
+}
+
+void UnistdGetppid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = getppid();
+}
+
+#if 0
+void UnistdGetsid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = getsid(Param[0]->Val->Integer);
+}
+#endif
+
+void UnistdGetuid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = getuid();
+}
+
+void UnistdGetwd(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Pointer = getcwd(Param[0]->Val->Pointer, PATH_MAX);
+}
+
+void UnistdIsatty(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = isatty(Param[0]->Val->Integer);
+}
+
+void UnistdLchown(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = lchown(Param[0]->Val->Pointer, Param[1]->Val->Integer, Param[2]->Val->Integer);
+}
+
+void UnistdLink(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = link(Param[0]->Val->Pointer, Param[1]->Val->Pointer);
+}
+
+void UnistdLockf(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = lockf(Param[0]->Val->Integer, Param[1]->Val->Integer, Param[2]->Val->Integer);
+}
+
+void UnistdLseek(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = lseek(Param[0]->Val->Integer, Param[1]->Val->Integer, Param[2]->Val->Integer);
+}
+
+void UnistdNice(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = nice(Param[0]->Val->Integer);
+}
+
+void UnistdPathconf(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = pathconf(Param[0]->Val->Pointer, Param[1]->Val->Integer);
+}
+
+void UnistdPause(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = pause();
+}
+
+#if 0
+void UnistdPread(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = pread(Param[0]->Val->Integer, Param[1]->Val->Pointer, Param[2]->Val->Integer, Param[3]->Val->Integer);
+}
+
+void UnistdPwrite(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = pwrite(Param[0]->Val->Integer, Param[1]->Val->Pointer, Param[2]->Val->Integer, Param[3]->Val->Integer);
+}
+#endif
+
+void UnistdRead(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = read(Param[0]->Val->Integer, Param[1]->Val->Pointer, Param[2]->Val->Integer);
+}
+
+void UnistdReadlink(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = readlink(Param[0]->Val->Pointer, Param[1]->Val->Pointer, Param[2]->Val->Integer);
+}
+
+void UnistdRmdir(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = rmdir(Param[0]->Val->Pointer);
+}
+
+void UnistdSbrk(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Pointer = sbrk(Param[0]->Val->Integer);
+}
+
+void UnistdSetgid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = setgid(Param[0]->Val->Integer);
+}
+
+void UnistdSetpgid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = setpgid(Param[0]->Val->Integer, Param[1]->Val->Integer);
+}
+
+void UnistdSetpgrp(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = setpgrp();
+}
+
+void UnistdSetregid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = setregid(Param[0]->Val->Integer, Param[1]->Val->Integer);
+}
+
+void UnistdSetreuid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = setreuid(Param[0]->Val->Integer, Param[1]->Val->Integer);
+}
+
+void UnistdSetsid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = setsid();
+}
+
+void UnistdSetuid(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = setuid(Param[0]->Val->Integer);
+}
+
+void UnistdSleep(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = sleep(Param[0]->Val->Integer);
+}
+
+#if 0
+void UnistdSwab(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = swab(Param[0]->Val->Pointer, Param[1]->Val->Pointer, Param[2]->Val->Integer);
+}
+#endif
+
+void UnistdSymlink(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = symlink(Param[0]->Val->Pointer, Param[1]->Val->Pointer);
+}
+
+void UnistdSync(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    sync();
+}
+
+void UnistdSysconf(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = sysconf(Param[0]->Val->Integer);
+}
+
+void UnistdTcgetpgrp(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = tcgetpgrp(Param[0]->Val->Integer);
+}
+
+void UnistdTcsetpgrp(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = tcsetpgrp(Param[0]->Val->Integer, Param[1]->Val->Integer);
+}
+
+void UnistdTruncate(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = truncate(Param[0]->Val->Pointer, Param[1]->Val->Integer);
+}
+
+void UnistdTtyname(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Pointer = ttyname(Param[0]->Val->Integer);
+}
+
+void UnistdTtyname_r(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = ttyname_r(Param[0]->Val->Integer, Param[1]->Val->Pointer, Param[2]->Val->Integer);
+}
+
+void UnistdUalarm(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = ualarm(Param[0]->Val->Integer, Param[1]->Val->Integer);
+}
+
+void UnistdUnlink(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = unlink(Param[0]->Val->Pointer);
+}
+
+void UnistdUsleep(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = usleep(Param[0]->Val->Integer);
+}
+
+void UnistdVfork(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = vfork();
+}
+
+void UnistdWrite(struct ParseState *Parser, struct Value *ReturnValue, struct Value **Param, int NumArgs)
+{
+    ReturnValue->Val->Integer = write(Param[0]->Val->Integer, Param[1]->Val->Pointer, Param[2]->Val->Integer);
+}
+
+
+/* handy structure definitions */
+const char UnistdDefs[] = "\
+typedef int uid_t; \
+typedef int gid_t; \
+typedef int pid_t; \
+typedef int off_t; \
+typedef int size_t; \
+typedef int ssize_t; \
+typedef int useconds_t;\
+typedef int intptr_t;\
+";
+
+/* all unistd.h functions */
+struct LibraryFunction UnistdFunctions[] =
+{
+    { UnistdAccess,        "int access(char *, int);" },
+    { UnistdAlarm,         "unsigned int alarm(unsigned int);" },
+    { UnistdBrk,           "int brk(void *);" },
+    { UnistdChdir,         "int chdir(char *);" },
+    { UnistdChroot,        "int chroot(char *);" },
+    { UnistdChown,         "int chown(char *, uid_t, gid_t);" },
+    { UnistdClose,         "int close(int);" },
+    { UnistdConfstr,       "size_t confstr(int, char *, size_t);" },
+    { UnistdCtermid,       "char *ctermid(char *);" },
+/*    { UnistdCuserid,       "char *cuserid(char *);" }, */
+    { UnistdDup,           "int dup(int);" },
+    { UnistdDup2,          "int dup2(int, int);" },
+/*     { UnistdEncrypt,       "void encrypt(char[64], int);" }, */
+/*    { UnistdExecl,         "int execl(char *, char *, ...);" }, */
+/*    { UnistdExecle,        "int execle(char *, char *, ...);" }, */
+/*    { UnistdExeclp,        "int execlp(char *, char *, ...);" }, */
+/*    { UnistdExecv,         "int execv(char *, char *[]);" }, */
+/*    { UnistdExecve,        "int execve(char *, char *[], char *[]);" }, */
+/*    { UnistdExecvp,        "int execvp(char *, char *[]);" }, */
+    { Unistd_Exit,         "void _exit(int);" },
+    { UnistdFchown,        "int fchown(int, uid_t, gid_t);" },
+    { UnistdFchdir,        "int fchdir(int);" },
+    { UnistdFdatasync,     "int fdatasync(int);" },
+    { UnistdFork,          "pid_t fork(void);" },
+    { UnistdFpathconf,     "long fpathconf(int, int);" },
+    { UnistdFsync,         "int fsync(int);" },
+    { UnistdFtruncate,     "int ftruncate(int, off_t);" },
+    { UnistdGetcwd,        "char *getcwd(char *, size_t);" },
+    { UnistdGetdtablesize, "int getdtablesize(void);" },
+    { UnistdGetegid,       "gid_t getegid(void);" },
+    { UnistdGeteuid,       "uid_t geteuid(void);" },
+    { UnistdGetgid,        "gid_t getgid(void);" },
+/*    { UnistdGetgroups,     "int getgroups(int, gid_t []);" }, */
+    { UnistdGethostid,     "long gethostid(void);" },
+    { UnistdGetlogin,      "char *getlogin(void);" },
+    { UnistdGetlogin_r,    "int getlogin_r(char *, size_t);" },
+/*    { UnistdGetopt,        "int getopt(int, char * [], char *);" }, */
+    { UnistdGetpagesize,   "int getpagesize(void);" },
+    { UnistdGetpass,       "char *getpass(char *);" },
+/*    { UnistdGetpgid,       "pid_t getpgid(pid_t);" }, */
+    { UnistdGetpgrp,       "pid_t getpgrp(void);" },
+    { UnistdGetpid,        "pid_t getpid(void);" },
+    { UnistdGetppid,       "pid_t getppid(void);" },
+/*    { UnistdGetsid,        "pid_t getsid(pid_t);" }, */
+    { UnistdGetuid,        "uid_t getuid(void);" },
+    { UnistdGetwd,         "char *getwd(char *);" },
+    { UnistdIsatty,        "int isatty(int);" },
+    { UnistdLchown,        "int lchown(char *, uid_t, gid_t);" },
+    { UnistdLink,          "int link(char *, char *);" },
+    { UnistdLockf,         "int lockf(int, int, off_t);" },
+    { UnistdLseek,         "off_t lseek(int, off_t, int);" },
+    { UnistdNice,          "int nice(int);" },
+    { UnistdPathconf,      "long pathconf(char *, int);" },
+    { UnistdPause,         "int pause(void);" },
+/*    { UnistdPipe,          "int pipe(int [2]);" }, */
+/*    { UnistdPread,         "ssize_t pread(int, void *, size_t, off_t);" }, */
+/*    { UnistdPthread_atfork,"int pthread_atfork(void (*)(void), void (*)(void), void(*)(void));" }, */
+/*    { UnistdPwrite,        "ssize_t pwrite(int, void *, size_t, off_t);" }, */
+    { UnistdRead,          "ssize_t read(int, void *, size_t);" },
+    { UnistdReadlink,      "int readlink(char *, char *, size_t);" },
+    { UnistdRmdir,         "int rmdir(char *);" },
+    { UnistdSbrk,          "void *sbrk(intptr_t);" },
+    { UnistdSetgid,        "int setgid(gid_t);" },
+    { UnistdSetpgid,       "int setpgid(pid_t, pid_t);" },
+    { UnistdSetpgrp,       "pid_t setpgrp(void);" },
+    { UnistdSetregid,      "int setregid(gid_t, gid_t);" },
+    { UnistdSetreuid,      "int setreuid(uid_t, uid_t);" },
+    { UnistdSetsid,        "pid_t setsid(void);" },
+    { UnistdSetuid,        "int setuid(uid_t);" },
+    { UnistdSleep,         "unsigned int sleep(unsigned int);" },
+/*    { UnistdSwab,          "void swab(void *, void *, ssize_t);" }, */
+    { UnistdSymlink,       "int symlink(char *, char *);" },
+    { UnistdSync,          "void sync(void);" },
+    { UnistdSysconf,       "long sysconf(int);" },
+    { UnistdTcgetpgrp,     "pid_t tcgetpgrp(int);" },
+    { UnistdTcsetpgrp,     "int tcsetpgrp(int, pid_t);" },
+    { UnistdTruncate,      "int truncate(char *, off_t);" },
+    { UnistdTtyname,       "char *ttyname(int);" },
+    { UnistdTtyname_r,     "int ttyname_r(int, char *, size_t);" },
+    { UnistdUalarm,        "useconds_t ualarm(useconds_t, useconds_t);" },
+    { UnistdUnlink,        "int unlink(char *);" },
+    { UnistdUsleep,        "int usleep(useconds_t);" },
+    { UnistdVfork,         "pid_t vfork(void);" },
+    { UnistdWrite,         "ssize_t write(int, void *, size_t);" },
+    { NULL,                 NULL }
+};
+
+/* creates various system-dependent definitions */
+void UnistdSetupFunc(void)
+{
+    /* define NULL */
+    if (!VariableDefined(TableStrRegister("NULL")))
+        VariableDefinePlatformVar(NULL, "NULL", &IntType, (union AnyValue *)&ZeroValue, FALSE);
+
+    /* define optarg and friends */
+    VariableDefinePlatformVar(NULL, "optarg", CharPtrType, (union AnyValue *)&optarg, TRUE);
+    VariableDefinePlatformVar(NULL, "optind", &IntType, (union AnyValue *)&optind, TRUE);
+    VariableDefinePlatformVar(NULL, "opterr", &IntType, (union AnyValue *)&opterr, TRUE);
+    VariableDefinePlatformVar(NULL, "optopt", &IntType, (union AnyValue *)&optopt, TRUE);
+}
+
+#endif /* !BUILTIN_MINI_STDLIB */
+
diff --git a/include.c b/include.c
index 93ef672..59bda9f 100644
--- a/include.c
+++ b/include.c
@@ -27,6 +27,7 @@ void IncludeInit()
     IncludeRegister("stdlib.h", &StdlibSetupFunc, &StdlibFunctions[0], NULL);
     IncludeRegister("string.h", &StringSetupFunc, &StringFunctions[0], NULL);
     IncludeRegister("time.h", &StdTimeSetupFunc, &StdTimeFunctions[0], StdTimeDefs);
+    IncludeRegister("unistd.h", &UnistdSetupFunc, &UnistdFunctions[0], UnistdDefs);
 #endif
 }
 
diff --git a/picoc.h b/picoc.h
index 78e6b32..e6dedc6 100644
--- a/picoc.h
+++ b/picoc.h
@@ -447,4 +447,9 @@ extern struct LibraryFunction StdCtypeFunctions[];
 extern const char StdboolDefs[];
 void StdboolSetupFunc(void);
 
+/* unistd.c */
+extern const char UnistdDefs[];
+extern struct LibraryFunction UnistdFunctions[];
+void UnistdSetupFunc(void);
+
 #endif /* PICOC_H */