os: implement and smoketest os.Chdir

src/os/file_anyos.go

@@ -27,6 +27,15 @@ const DevNull = "/dev/null"
 // filesystem support.
 const isOS = true
 
+// Chdir changes the current working directory to the named directory.
+// If there is an error, it will be of type *PathError.
+func Chdir(dir string) error {
+	if e := syscall.Chdir(dir); e != nil {
+		return &PathError{Op: "chdir", Path: dir, Err: e}
+	}
+	return nil
+}
+
 // unixFilesystem is an empty handle for a Unix/Linux filesystem. All operations
 // are relative to the current working directory.
 type unixFilesystem struct {

src/os/file_anyos_test.go

@@ -1,3 +1,5 @@
+// +build !baremetal,!js
+
 package os_test
 
 import (
@@ -23,3 +25,45 @@ func TestTempDir(t *testing.T) {
 		t.Errorf("Remove %s: %s", name, err)
 	}
 }
+
+func TestChdir(t *testing.T) {
+	// create and cd into a new directory
+	dir := "_os_test_TestChDir"
+	Remove(dir)
+	err := Mkdir(dir, 0755)
+	defer Remove(dir) // even though not quite sure which directory it will execute in
+	if err != nil {
+		t.Errorf("Mkdir(%s, 0755) returned %v", dir, err)
+	}
+	err = Chdir(dir)
+	if err != nil {
+		t.Fatalf("Chdir %s: %s", dir, err)
+		return
+	}
+	// create a file there
+	file := "_os_test_TestTempDir.dat"
+	f, err := OpenFile(file, O_RDWR|O_CREATE, 0644)
+	if err != nil {
+		t.Errorf("OpenFile %s: %s", file, err)
+	}
+	defer Remove(file) // even though not quite sure which directory it will execute in
+	err = f.Close()
+	if err != nil {
+		t.Errorf("Close %s: %s", file, err)
+	}
+	// cd back to original directory
+	err = Chdir("..")
+	if err != nil {
+		t.Errorf("Chdir ..: %s", err)
+	}
+	// clean up file and directory explicitly so we can check for errors
+	fullname := dir + "/" + file
+	err = Remove(fullname)
+	if err != nil {
+		t.Errorf("Remove %s: %s", fullname, err)
+	}
+	err = Remove(dir)
+	if err != nil {
+		t.Errorf("Remove %s: %s", dir, err)
+	}
+}

src/syscall/syscall_libc.go

@@ -59,6 +59,15 @@ func Open(path string, flag int, mode uint32) (fd int, err error) {
 	return
 }
 
+func Chdir(path string) (err error) {
+	data := cstring(path)
+	fail := int(libc_chdir(&data[0]))
+	if fail < 0 {
+		err = getErrno()
+	}
+	return
+}
+
 func Mkdir(path string, mode uint32) (err error) {
 	data := cstring(path)
 	fail := int(libc_mkdir(&data[0], mode))
@@ -198,6 +207,10 @@ func libc_mmap(addr unsafe.Pointer, length uintptr, prot, flags, fd int32, offse
 //export mprotect
 func libc_mprotect(addr unsafe.Pointer, len uintptr, prot int32) int32
 
+// int chdir(const char *pathname, mode_t mode);
+//export chdir
+func libc_chdir(pathname *byte) int32
+
 // int mkdir(const char *pathname, mode_t mode);
 //export mkdir
 func libc_mkdir(pathname *byte, mode uint32) int32