Add sys$ttyname_r and ttyname_r() + ttyname().

And print a greeting when sh starts up so we know which TTY we're on.

Kernel/Syscall.cpp

@@ -114,6 +114,8 @@ DWORD handle(DWORD function, DWORD arg1, DWORD arg2, DWORD arg3)
         return current->sys$set_mmap_name((void*)arg1, (size_t)arg2, (const char*)arg3);
     case Syscall::PosixReadlink:
         return current->sys$readlink((const char*)arg1, (char*)arg2, (size_t)arg3);
+    case Syscall::PosixTtynameR:
+        return current->sys$ttyname_r((int)arg1, (char*)arg2, (size_t)arg3);
     default:
         kprintf("int0x80: Unknown function %x requested {%x, %x, %x}\n", function, arg1, arg2, arg3);
         break;

Kernel/Syscall.h

@@ -37,6 +37,7 @@ enum Function {
     SetMmapName = 0x2005,
     PosixReadlink = 0x2006,
     PosixWrite = 0x2007,
+    PosixTtynameR = 0x2008,
 };
 
 void initialize();

Kernel/TTY.h

@@ -13,6 +13,8 @@ public:
     virtual String ttyName() const = 0;
 
 protected:
+    virtual bool isTTY() const final { return true; }
+
     TTY(unsigned major, unsigned minor);
     void emit(byte);
 

Kernel/Task.cpp

@@ -741,7 +741,7 @@ ssize_t Task::sys$get_dir_entries(int fd, void* buffer, size_t size)
     VALIDATE_USER_BUFFER(buffer, size);
     auto* handle = fileHandleIfExists(fd);
     if (!handle)
-        return -1;
+        return -EBADF;
     return handle->get_dir_entries((byte*)buffer, size);
 }
 
@@ -749,10 +749,25 @@ int Task::sys$seek(int fd, int offset)
 {
     auto* handle = fileHandleIfExists(fd);
     if (!handle)
-        return -1;
+        return -EBADF;
     return handle->seek(offset, SEEK_SET);
 }
 
+int Task::sys$ttyname_r(int fd, char* buffer, size_t size)
+{
+    VALIDATE_USER_BUFFER(buffer, size);
+    auto* handle = fileHandleIfExists(fd);
+    if (!handle)
+        return -EBADF;
+    if (!handle->isTTY())
+        return -ENOTTY;
+    auto ttyName = handle->tty()->ttyName();
+    if (size < ttyName.length() + 1)
+        return -ERANGE;
+    strcpy(buffer, ttyName.characters());
+    return 0;
+}
+
 ssize_t Task::sys$write(int fd, const void* data, size_t size)
 {
     VALIDATE_USER_BUFFER(data, size);
@@ -802,7 +817,7 @@ int Task::sys$close(int fd)
 {
     auto* handle = fileHandleIfExists(fd);
     if (!handle)
-        return -1;
+        return -EBADF;
     // FIXME: Implement.
     return 0;
 }

Kernel/Task.h

@@ -111,6 +111,7 @@ public:
     int sys$get_arguments(int* argc, char*** argv);
     int sys$uname(utsname*);
     int sys$readlink(const char*, char*, size_t);
+    int sys$ttyname_r(int fd, char*, size_t);
 
     static void initialize();