Code Examples
package main
import (
"log"
"os"
)
func main() {
if err := os.Chmod("some-filename", 0644); err != nil {
log.Fatal(err)
}
}
package main
import (
"log"
"os"
"time"
)
func main() {
mtime := time.Date(2006, time.February, 1, 3, 4, 5, 0, time.UTC)
atime := time.Date(2007, time.March, 2, 4, 5, 6, 0, time.UTC)
if err := os.Chtimes("some-filename", atime, mtime); err != nil {
log.Fatal(err)
}
}
package main
import (
"log"
"os"
)
func main() {
f, err := os.CreateTemp("", "example")
if err != nil {
log.Fatal(err)
}
defer os.Remove(f.Name()) // clean up
if _, err := f.Write([]byte("content")); err != nil {
log.Fatal(err)
}
if err := f.Close(); err != nil {
log.Fatal(err)
}
}
package main
import (
"log"
"os"
)
func main() {
f, err := os.CreateTemp("", "example.*.txt")
if err != nil {
log.Fatal(err)
}
defer os.Remove(f.Name()) // clean up
if _, err := f.Write([]byte("content")); err != nil {
f.Close()
log.Fatal(err)
}
if err := f.Close(); err != nil {
log.Fatal(err)
}
}
package main
import (
"errors"
"fmt"
"io/fs"
"os"
)
func main() {
filename := "a-nonexistent-file"
if _, err := os.Stat(filename); errors.Is(err, fs.ErrNotExist) {
fmt.Println("file does not exist")
}
}
package main
import (
"fmt"
"os"
)
func main() {
mapper := func(placeholderName string) string {
switch placeholderName {
case "DAY_PART":
return "morning"
case "NAME":
return "Gopher"
}
return ""
}
fmt.Println(os.Expand("Good ${DAY_PART}, $NAME!", mapper))
}
package main
import (
"fmt"
"os"
)
func main() {
os.Setenv("NAME", "gopher")
os.Setenv("BURROW", "/usr/gopher")
fmt.Println(os.ExpandEnv("$NAME lives in ${BURROW}."))
}
package main
import (
"fmt"
"io/fs"
"log"
"os"
)
func main() {
fi, err := os.Lstat("some-filename")
if err != nil {
log.Fatal(err)
}
fmt.Printf("permissions: %#o\n", fi.Mode().Perm()) // 0o400, 0o777, etc.
switch mode := fi.Mode(); {
case mode.IsRegular():
fmt.Println("regular file")
case mode.IsDir():
fmt.Println("directory")
case mode&fs.ModeSymlink != 0:
fmt.Println("symbolic link")
case mode&fs.ModeNamedPipe != 0:
fmt.Println("named pipe")
}
}
package main
import (
"fmt"
"os"
)
func main() {
os.Setenv("NAME", "gopher")
os.Setenv("BURROW", "/usr/gopher")
fmt.Printf("%s lives in %s.\n", os.Getenv("NAME"), os.Getenv("BURROW"))
}
package main
import (
"fmt"
"os"
)
func main() {
show := func(key string) {
val, ok := os.LookupEnv(key)
if !ok {
fmt.Printf("%s not set\n", key)
} else {
fmt.Printf("%s=%s\n", key, val)
}
}
os.Setenv("SOME_KEY", "value")
os.Setenv("EMPTY_KEY", "")
show("SOME_KEY")
show("EMPTY_KEY")
show("MISSING_KEY")
}
package main
import (
"log"
"os"
)
func main() {
err := os.Mkdir("testdir", 0750)
if err != nil && !os.IsExist(err) {
log.Fatal(err)
}
err = os.WriteFile("testdir/testfile.txt", []byte("Hello, Gophers!"), 0660)
if err != nil {
log.Fatal(err)
}
}
package main
import (
"log"
"os"
)
func main() {
err := os.MkdirAll("test/subdir", 0750)
if err != nil {
log.Fatal(err)
}
err = os.WriteFile("test/subdir/testfile.txt", []byte("Hello, Gophers!"), 0660)
if err != nil {
log.Fatal(err)
}
}
package main
import (
"log"
"os"
"path/filepath"
)
func main() {
dir, err := os.MkdirTemp("", "example")
if err != nil {
log.Fatal(err)
}
defer os.RemoveAll(dir) // clean up
file := filepath.Join(dir, "tmpfile")
if err := os.WriteFile(file, []byte("content"), 0666); err != nil {
log.Fatal(err)
}
}
package main
import (
"log"
"os"
"path/filepath"
)
func main() {
logsDir, err := os.MkdirTemp("", "*-logs")
if err != nil {
log.Fatal(err)
}
defer os.RemoveAll(logsDir) // clean up
// Logs can be cleaned out earlier if needed by searching
// for all directories whose suffix ends in *-logs.
globPattern := filepath.Join(os.TempDir(), "*-logs")
matches, err := filepath.Glob(globPattern)
if err != nil {
log.Fatalf("Failed to match %q: %v", globPattern, err)
}
for _, match := range matches {
if err := os.RemoveAll(match); err != nil {
log.Printf("Failed to remove %q: %v", match, err)
}
}
}
package main
import (
"log"
"os"
)
func main() {
f, err := os.OpenFile("notes.txt", os.O_RDWR|os.O_CREATE, 0644)
if err != nil {
log.Fatal(err)
}
if err := f.Close(); err != nil {
log.Fatal(err)
}
}
package main
import (
"log"
"os"
)
func main() {
// If the file doesn't exist, create it, or append to the file
f, err := os.OpenFile("access.log", os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
if err != nil {
log.Fatal(err)
}
if _, err := f.Write([]byte("appended some data\n")); err != nil {
f.Close() // ignore error; Write error takes precedence
log.Fatal(err)
}
if err := f.Close(); err != nil {
log.Fatal(err)
}
}
package main
import (
"fmt"
"log"
"os"
)
func main() {
files, err := os.ReadDir(".")
if err != nil {
log.Fatal(err)
}
for _, file := range files {
fmt.Println(file.Name())
}
}
package main
import (
"log"
"os"
)
func main() {
data, err := os.ReadFile("testdata/hello")
if err != nil {
log.Fatal(err)
}
os.Stdout.Write(data)
}
package main
import (
"errors"
"fmt"
"log"
"os"
"path/filepath"
)
func main() {
// First, we create a relative symlink to a file.
d, err := os.MkdirTemp("", "")
if err != nil {
log.Fatal(err)
}
defer os.RemoveAll(d)
targetPath := filepath.Join(d, "hello.txt")
if err := os.WriteFile(targetPath, []byte("Hello, Gophers!"), 0644); err != nil {
log.Fatal(err)
}
linkPath := filepath.Join(d, "hello.link")
if err := os.Symlink("hello.txt", filepath.Join(d, "hello.link")); err != nil {
if errors.Is(err, errors.ErrUnsupported) {
// Allow the example to run on platforms that do not support symbolic links.
fmt.Printf("%s links to %s\n", filepath.Base(linkPath), "hello.txt")
return
}
log.Fatal(err)
}
// Readlink returns the relative path as passed to os.Symlink.
dst, err := os.Readlink(linkPath)
if err != nil {
log.Fatal(err)
}
fmt.Printf("%s links to %s\n", filepath.Base(linkPath), dst)
var dstAbs string
if filepath.IsAbs(dst) {
dstAbs = dst
} else {
// Symlink targets are relative to the directory containing the link.
dstAbs = filepath.Join(filepath.Dir(linkPath), dst)
}
// Check that the target is correct by comparing it with os.Stat
// on the original target path.
dstInfo, err := os.Stat(dstAbs)
if err != nil {
log.Fatal(err)
}
targetInfo, err := os.Stat(targetPath)
if err != nil {
log.Fatal(err)
}
if !os.SameFile(dstInfo, targetInfo) {
log.Fatalf("link destination (%s) is not the same file as %s", dstAbs, targetPath)
}
}
package main
import (
"os"
)
func main() {
os.Setenv("TMPDIR", "/my/tmp")
defer os.Unsetenv("TMPDIR")
}
package main
import (
"log"
"os"
"path/filepath"
"sync"
)
func main() {
dir, dirErr := os.UserCacheDir()
if dirErr == nil {
dir = filepath.Join(dir, "ExampleUserCacheDir")
}
getCache := func(name string) ([]byte, error) {
if dirErr != nil {
return nil, &os.PathError{Op: "getCache", Path: name, Err: os.ErrNotExist}
}
return os.ReadFile(filepath.Join(dir, name))
}
var mkdirOnce sync.Once
putCache := func(name string, b []byte) error {
if dirErr != nil {
return &os.PathError{Op: "putCache", Path: name, Err: dirErr}
}
mkdirOnce.Do(func() {
if err := os.MkdirAll(dir, 0700); err != nil {
log.Printf("can't create user cache dir: %v", err)
}
})
return os.WriteFile(filepath.Join(dir, name), b, 0600)
}
// Read and store cached data.
// …
_ = getCache
_ = putCache
}
package main
import (
"bytes"
"log"
"os"
"path/filepath"
)
func main() {
dir, dirErr := os.UserConfigDir()
var (
configPath string
origConfig []byte
)
if dirErr == nil {
configPath = filepath.Join(dir, "ExampleUserConfigDir", "example.conf")
var err error
origConfig, err = os.ReadFile(configPath)
if err != nil && !os.IsNotExist(err) {
// The user has a config file but we couldn't read it.
// Report the error instead of ignoring their configuration.
log.Fatal(err)
}
}
// Use and perhaps make changes to the config.
config := bytes.Clone(origConfig)
// …
// Save changes.
if !bytes.Equal(config, origConfig) {
if configPath == "" {
log.Printf("not saving config changes: %v", dirErr)
} else {
err := os.MkdirAll(filepath.Dir(configPath), 0700)
if err == nil {
err = os.WriteFile(configPath, config, 0600)
}
if err != nil {
log.Printf("error saving config changes: %v", err)
}
}
}
}
package main
import (
"log"
"os"
)
func main() {
err := os.WriteFile("testdata/hello", []byte("Hello, Gophers!"), 0666)
if err != nil {
log.Fatal(err)
}
}
Package-Level Type Names (total 12)
/* sort by: | */
A DirEntry is an entry read from a directory
(using the [ReadDir] function or a [File.ReadDir] method).
File represents an open file descriptor.
The methods of File are safe for concurrent use. Chdir changes the current working directory to the file,
which must be a directory.
If there is an error, it will be of type [*PathError]. Chmod changes the mode of the file to mode.
If there is an error, it will be of type *PathError. Chown changes the numeric uid and gid of the named file.
If there is an error, it will be of type [*PathError].
On Windows, it always returns the [syscall.EWINDOWS] error, wrapped
in *PathError. Close closes the [File], rendering it unusable for I/O.
On files that support [File.SetDeadline], any pending I/O operations will
be canceled and return immediately with an [ErrClosed] error.
Close will return an error if it has already been called. Fd returns the integer Unix file descriptor referencing the open file.
If f is closed, the file descriptor becomes invalid.
If f is garbage collected, a finalizer may close the file descriptor,
making it invalid; see [runtime.SetFinalizer] for more information on when
a finalizer might be run. On Unix systems this will cause the [File.SetDeadline]
methods to stop working.
Because file descriptors can be reused, the returned file descriptor may
only be closed through the [File.Close] method of f, or by its finalizer during
garbage collection. Otherwise, during garbage collection the finalizer
may close an unrelated file descriptor with the same (reused) number.
As an alternative, see the f.SyscallConn method. Name returns the name of the file as presented to Open.
It is safe to call Name after [Close]. Read reads up to len(b) bytes from the File and stores them in b.
It returns the number of bytes read and any error encountered.
At end of file, Read returns 0, io.EOF. ReadAt reads len(b) bytes from the File starting at byte offset off.
It returns the number of bytes read and the error, if any.
ReadAt always returns a non-nil error when n < len(b).
At end of file, that error is io.EOF. ReadDir reads the contents of the directory associated with the file f
and returns a slice of [DirEntry] values in directory order.
Subsequent calls on the same file will yield later DirEntry records in the directory.
If n > 0, ReadDir returns at most n DirEntry records.
In this case, if ReadDir returns an empty slice, it will return an error explaining why.
At the end of a directory, the error is [io.EOF].
If n <= 0, ReadDir returns all the DirEntry records remaining in the directory.
When it succeeds, it returns a nil error (not io.EOF). ReadFrom implements io.ReaderFrom. Readdir reads the contents of the directory associated with file and
returns a slice of up to n [FileInfo] values, as would be returned
by [Lstat], in directory order. Subsequent calls on the same file will yield
further FileInfos.
If n > 0, Readdir returns at most n FileInfo structures. In this case, if
Readdir returns an empty slice, it will return a non-nil error
explaining why. At the end of a directory, the error is [io.EOF].
If n <= 0, Readdir returns all the FileInfo from the directory in
a single slice. In this case, if Readdir succeeds (reads all
the way to the end of the directory), it returns the slice and a
nil error. If it encounters an error before the end of the
directory, Readdir returns the FileInfo read until that point
and a non-nil error.
Most clients are better served by the more efficient ReadDir method. Readdirnames reads the contents of the directory associated with file
and returns a slice of up to n names of files in the directory,
in directory order. Subsequent calls on the same file will yield
further names.
If n > 0, Readdirnames returns at most n names. In this case, if
Readdirnames returns an empty slice, it will return a non-nil error
explaining why. At the end of a directory, the error is [io.EOF].
If n <= 0, Readdirnames returns all the names from the directory in
a single slice. In this case, if Readdirnames succeeds (reads all
the way to the end of the directory), it returns the slice and a
nil error. If it encounters an error before the end of the
directory, Readdirnames returns the names read until that point and
a non-nil error. Seek sets the offset for the next Read or Write on file to offset, interpreted
according to whence: 0 means relative to the origin of the file, 1 means
relative to the current offset, and 2 means relative to the end.
It returns the new offset and an error, if any.
The behavior of Seek on a file opened with O_APPEND is not specified. SetDeadline sets the read and write deadlines for a File.
It is equivalent to calling both SetReadDeadline and SetWriteDeadline.
Only some kinds of files support setting a deadline. Calls to SetDeadline
for files that do not support deadlines will return ErrNoDeadline.
On most systems ordinary files do not support deadlines, but pipes do.
A deadline is an absolute time after which I/O operations fail with an
error instead of blocking. The deadline applies to all future and pending
I/O, not just the immediately following call to Read or Write.
After a deadline has been exceeded, the connection can be refreshed
by setting a deadline in the future.
If the deadline is exceeded a call to Read or Write or to other I/O
methods will return an error that wraps ErrDeadlineExceeded.
This can be tested using errors.Is(err, os.ErrDeadlineExceeded).
That error implements the Timeout method, and calling the Timeout
method will return true, but there are other possible errors for which
the Timeout will return true even if the deadline has not been exceeded.
An idle timeout can be implemented by repeatedly extending
the deadline after successful Read or Write calls.
A zero value for t means I/O operations will not time out. SetReadDeadline sets the deadline for future Read calls and any
currently-blocked Read call.
A zero value for t means Read will not time out.
Not all files support setting deadlines; see SetDeadline. SetWriteDeadline sets the deadline for any future Write calls and any
currently-blocked Write call.
Even if Write times out, it may return n > 0, indicating that
some of the data was successfully written.
A zero value for t means Write will not time out.
Not all files support setting deadlines; see SetDeadline. Stat returns the [FileInfo] structure describing file.
If there is an error, it will be of type [*PathError]. Sync commits the current contents of the file to stable storage.
Typically, this means flushing the file system's in-memory copy
of recently written data to disk. SyscallConn returns a raw file.
This implements the syscall.Conn interface. Truncate changes the size of the file.
It does not change the I/O offset.
If there is an error, it will be of type [*PathError]. Write writes len(b) bytes from b to the File.
It returns the number of bytes written and an error, if any.
Write returns a non-nil error when n != len(b). WriteAt writes len(b) bytes to the File starting at byte offset off.
It returns the number of bytes written and an error, if any.
WriteAt returns a non-nil error when n != len(b).
If file was opened with the O_APPEND flag, WriteAt returns an error. WriteString is like Write, but writes the contents of string s rather than
a slice of bytes. WriteTo implements io.WriterTo.
*File : internal/bisect.Writer
*File : io.Closer
*File : io.ReadCloser
*File : io.Reader
*File : io.ReaderAt
*File : io.ReaderFrom
*File : io.ReadSeekCloser
*File : io.ReadSeeker
*File : io.ReadWriteCloser
*File : io.ReadWriter
*File : io.ReadWriteSeeker
*File : io.Seeker
*File : io.StringWriter
*File : io.WriteCloser
*File : io.Writer
*File : io.WriterAt
*File : io.WriterTo
*File : io.WriteSeeker
*File : io/fs.File
*File : io/fs.ReadDirFile
*File : mime/multipart.File
*File : net/http.File
*File : syscall.Conn
func Create(name string) (*File, error)
func CreateTemp(dir, pattern string) (*File, error)
func NewFile(fd uintptr, name string) *File
func Open(name string) (*File, error)
func OpenFile(name string, flag int, perm FileMode) (*File, error)
func OpenInRoot(dir, name string) (*File, error)
func Pipe() (r *File, w *File, err error)
func Pipe() (r *File, w *File, err error)
func (*Root).Create(name string) (*File, error)
func (*Root).Open(name string) (*File, error)
func (*Root).OpenFile(name string, flag int, perm FileMode) (*File, error)
func internal/testpty.Open() (pty *File, processTTY string, err error)
func io/ioutil.TempFile(dir, pattern string) (f *File, err error)
func net.(*TCPListener).File() (f *File, err error)
func net.(*UnixListener).File() (f *File, err error)
func internal/coverage/decodemeta.NewCoverageMetaFileReader(f *File, fileView []byte) (*decodemeta.CoverageMetaFileReader, error)
func net.FileConn(f *File) (c net.Conn, err error)
func net.FileListener(f *File) (ln net.Listener, err error)
func net.FilePacketConn(f *File) (c net.PacketConn, err error)
func runtime/debug.SetCrashOutput(f *File, opts debug.CrashOptions) error
var Stderr *File
var Stdin *File
var Stdout *File
A FileInfo describes a file and is returned by [Stat] and [Lstat].
A FileMode represents a file's mode and permission bits.
The bits have the same definition on all systems, so that
information about files can be moved from one system
to another portably. Not all bits apply to all systems.
The only required bit is [ModeDir] for directories.
PathError records an error and the operation and file path that caused it.
ProcAttr holds the attributes that will be applied to a new process
started by StartProcess. If Dir is non-empty, the child changes into the directory before
creating the process. If Env is non-nil, it gives the environment variables for the
new process in the form returned by Environ.
If it is nil, the result of Environ will be used. Files specifies the open files inherited by the new process. The
first three entries correspond to standard input, standard output, and
standard error. An implementation may support additional entries,
depending on the underlying operating system. A nil entry corresponds
to that file being closed when the process starts.
On Unix systems, StartProcess will change these File values
to blocking mode, which means that SetDeadline will stop working
and calling Close will not interrupt a Read or Write. Operating system-specific process creation attributes.
Note that setting this field means that your program
may not execute properly or even compile on some
operating systems.
func StartProcess(name string, argv []string, attr *ProcAttr) (*Process, error)
Process stores the information about a process created by [StartProcess].Pidint Kill causes the [Process] to exit immediately. Kill does not wait until
the Process has actually exited. This only kills the Process itself,
not any other processes it may have started. Release releases any resources associated with the [Process] p,
rendering it unusable in the future.
Release only needs to be called if [Process.Wait] is not. Signal sends a signal to the [Process].
Sending [Interrupt] on Windows is not implemented. Wait waits for the [Process] to exit, and then returns a
ProcessState describing its status and an error, if any.
Wait releases any resources associated with the Process.
On most operating systems, the Process must be a child
of the current process or an error will be returned.
func FindProcess(pid int) (*Process, error)
func StartProcess(name string, argv []string, attr *ProcAttr) (*Process, error)
ProcessState stores information about a process, as reported by Wait. ExitCode returns the exit code of the exited process, or -1
if the process hasn't exited or was terminated by a signal. Exited reports whether the program has exited.
On Unix systems this reports true if the program exited due to calling exit,
but false if the program terminated due to a signal. Pid returns the process id of the exited process.(*ProcessState) String() string Success reports whether the program exited successfully,
such as with exit status 0 on Unix. Sys returns system-dependent exit information about
the process. Convert it to the appropriate underlying
type, such as [syscall.WaitStatus] on Unix, to access its contents. SysUsage returns system-dependent resource usage information about
the exited process. Convert it to the appropriate underlying
type, such as [*syscall.Rusage] on Unix, to access its contents.
(On Unix, *syscall.Rusage matches struct rusage as defined in the
getrusage(2) manual page.) SystemTime returns the system CPU time of the exited process and its children. UserTime returns the user CPU time of the exited process and its children.
*ProcessState : expvar.Var
*ProcessState : fmt.Stringer
func (*Process).Wait() (*ProcessState, error)
Root may be used to only access files within a single directory tree.
Methods on Root can only access files and directories beneath a root directory.
If any component of a file name passed to a method of Root references a location
outside the root, the method returns an error.
File names may reference the directory itself (.).
Methods on Root will follow symbolic links, but symbolic links may not
reference a location outside the root.
Symbolic links must not be absolute.
Methods on Root do not prohibit traversal of filesystem boundaries,
Linux bind mounts, /proc special files, or access to Unix device files.
Methods on Root are safe to be used from multiple goroutines simultaneously.
On most platforms, creating a Root opens a file descriptor or handle referencing
the directory. If the directory is moved, methods on Root reference the original
directory in its new location.
Root's behavior differs on some platforms:
- When GOOS=windows, file names may not reference Windows reserved device names
such as NUL and COM1.
- When GOOS=js, Root is vulnerable to TOCTOU (time-of-check-time-of-use)
attacks in symlink validation, and cannot ensure that operations will not
escape the root.
- When GOOS=plan9 or GOOS=js, Root does not track directories across renames.
On these platforms, a Root references a directory name, not a file descriptor. Close closes the Root.
After Close is called, methods on Root return errors. Create creates or truncates the named file in the root.
See [Create] for more details. FS returns a file system (an fs.FS) for the tree of files in the root.
The result implements [io/fs.StatFS], [io/fs.ReadFileFS] and
[io/fs.ReadDirFS]. Lstat returns a [FileInfo] describing the named file in the root.
If the file is a symbolic link, the returned FileInfo
describes the symbolic link.
See [Lstat] for more details. Mkdir creates a new directory in the root
with the specified name and permission bits (before umask).
See [Mkdir] for more details.
If perm contains bits other than the nine least-significant bits (0o777),
OpenFile returns an error. Name returns the name of the directory presented to OpenRoot.
It is safe to call Name after [Close]. Open opens the named file in the root for reading.
See [Open] for more details. OpenFile opens the named file in the root.
See [OpenFile] for more details.
If perm contains bits other than the nine least-significant bits (0o777),
OpenFile returns an error. OpenRoot opens the named directory in the root.
If there is an error, it will be of type *PathError. Remove removes the named file or (empty) directory in the root.
See [Remove] for more details. Stat returns a [FileInfo] describing the named file in the root.
See [Stat] for more details.
*Root : io.Closer
func OpenRoot(name string) (*Root, error)
func (*Root).OpenRoot(name string) (*Root, error)
A Signal represents an operating system signal.
The usual underlying implementation is operating system-dependent:
on Unix it is syscall.Signal. // to distinguish from other Stringers( Signal) String() string
syscall.Signal
Signal : expvar.Var
Signal : fmt.Stringer
func (*Process).Signal(sig Signal) error
func os/signal.Ignore(sig ...Signal)
func os/signal.Ignored(sig Signal) bool
func os/signal.Notify(c chan<- Signal, sig ...Signal)
func os/signal.Notify(c chan<- Signal, sig ...Signal)
func os/signal.NotifyContext(parent context.Context, signals ...Signal) (ctx context.Context, stop context.CancelFunc)
func os/signal.Reset(sig ...Signal)
func os/signal.Stop(c chan<- Signal)
var Interrupt
var Kill
SyscallError records an error from a specific system call.ErrerrorSyscallstring(*SyscallError) Error() string Timeout reports whether this error represents a timeout.(*SyscallError) Unwrap() error
*SyscallError : error
Package-Level Functions (total 63)
Chdir changes the current working directory to the named directory.
If there is an error, it will be of type *PathError.
Chmod changes the mode of the named file to mode.
If the file is a symbolic link, it changes the mode of the link's target.
If there is an error, it will be of type *PathError.
A different subset of the mode bits are used, depending on the
operating system.
On Unix, the mode's permission bits, ModeSetuid, ModeSetgid, and
ModeSticky are used.
On Windows, only the 0o200 bit (owner writable) of mode is used; it
controls whether the file's read-only attribute is set or cleared.
The other bits are currently unused. For compatibility with Go 1.12
and earlier, use a non-zero mode. Use mode 0o400 for a read-only
file and 0o600 for a readable+writable file.
On Plan 9, the mode's permission bits, ModeAppend, ModeExclusive,
and ModeTemporary are used.
Chown changes the numeric uid and gid of the named file.
If the file is a symbolic link, it changes the uid and gid of the link's target.
A uid or gid of -1 means to not change that value.
If there is an error, it will be of type [*PathError].
On Windows or Plan 9, Chown always returns the [syscall.EWINDOWS] or
EPLAN9 error, wrapped in *PathError.
Chtimes changes the access and modification times of the named
file, similar to the Unix utime() or utimes() functions.
A zero [time.Time] value will leave the corresponding file time unchanged.
The underlying filesystem may truncate or round the values to a
less precise time unit.
If there is an error, it will be of type [*PathError].
Clearenv deletes all environment variables.
CopyFS copies the file system fsys into the directory dir,
creating dir if necessary.
Files are created with mode 0o666 plus any execute permissions
from the source, and directories are created with mode 0o777
(before umask).
CopyFS will not overwrite existing files. If a file name in fsys
already exists in the destination, CopyFS will return an error
such that errors.Is(err, fs.ErrExist) will be true.
Symbolic links in fsys are not supported. A *PathError with Err set
to ErrInvalid is returned when copying from a symbolic link.
Symbolic links in dir are followed.
Copying stops at and returns the first error encountered.
Create creates or truncates the named file. If the file already exists,
it is truncated. If the file does not exist, it is created with mode 0o666
(before umask). If successful, methods on the returned File can
be used for I/O; the associated file descriptor has mode O_RDWR.
The directory containing the file must already exist.
If there is an error, it will be of type *PathError.
CreateTemp creates a new temporary file in the directory dir,
opens the file for reading and writing, and returns the resulting file.
The filename is generated by taking pattern and adding a random string to the end.
If pattern includes a "*", the random string replaces the last "*".
The file is created with mode 0o600 (before umask).
If dir is the empty string, CreateTemp uses the default directory for temporary files, as returned by [TempDir].
Multiple programs or goroutines calling CreateTemp simultaneously will not choose the same file.
The caller can use the file's Name method to find the pathname of the file.
It is the caller's responsibility to remove the file when it is no longer needed.
DirFS returns a file system (an fs.FS) for the tree of files rooted at the directory dir.
Note that DirFS("/prefix") only guarantees that the Open calls it makes to the
operating system will begin with "/prefix": DirFS("/prefix").Open("file") is the
same as os.Open("/prefix/file"). So if /prefix/file is a symbolic link pointing outside
the /prefix tree, then using DirFS does not stop the access any more than using
os.Open does. Additionally, the root of the fs.FS returned for a relative path,
DirFS("prefix"), will be affected by later calls to Chdir. DirFS is therefore not
a general substitute for a chroot-style security mechanism when the directory tree
contains arbitrary content.
Use [Root.FS] to obtain a fs.FS that prevents escapes from the tree via symbolic links.
The directory dir must not be "".
The result implements [io/fs.StatFS], [io/fs.ReadFileFS] and
[io/fs.ReadDirFS].
Environ returns a copy of strings representing the environment,
in the form "key=value".
Executable returns the path name for the executable that started
the current process. There is no guarantee that the path is still
pointing to the correct executable. If a symlink was used to start
the process, depending on the operating system, the result might
be the symlink or the path it pointed to. If a stable result is
needed, [path/filepath.EvalSymlinks] might help.
Executable returns an absolute path unless an error occurred.
The main use case is finding resources located relative to an
executable.
Exit causes the current program to exit with the given status code.
Conventionally, code zero indicates success, non-zero an error.
The program terminates immediately; deferred functions are not run.
For portability, the status code should be in the range [0, 125].
Expand replaces ${var} or $var in the string based on the mapping function.
For example, [os.ExpandEnv](s) is equivalent to [os.Expand](s, [os.Getenv]).
ExpandEnv replaces ${var} or $var in the string according to the values
of the current environment variables. References to undefined
variables are replaced by the empty string.
FindProcess looks for a running process by its pid.
The [Process] it returns can be used to obtain information
about the underlying operating system process.
On Unix systems, FindProcess always succeeds and returns a Process
for the given pid, regardless of whether the process exists. To test whether
the process actually exists, see whether p.Signal(syscall.Signal(0)) reports
an error.
Getegid returns the numeric effective group id of the caller.
On Windows, it returns -1.
Getenv retrieves the value of the environment variable named by the key.
It returns the value, which will be empty if the variable is not present.
To distinguish between an empty value and an unset value, use [LookupEnv].
Geteuid returns the numeric effective user id of the caller.
On Windows, it returns -1.
Getgid returns the numeric group id of the caller.
On Windows, it returns -1.
Getgroups returns a list of the numeric ids of groups that the caller belongs to.
On Windows, it returns [syscall.EWINDOWS]. See the [os/user] package
for a possible alternative.
Getpagesize returns the underlying system's memory page size.
Getpid returns the process id of the caller.
Getppid returns the process id of the caller's parent.
Getuid returns the numeric user id of the caller.
On Windows, it returns -1.
Getwd returns an absolute path name corresponding to the
current directory. If the current directory can be
reached via multiple paths (due to symbolic links),
Getwd may return any one of them.
On Unix platforms, if the environment variable PWD
provides an absolute name, and it is a name of the
current directory, it is returned.
Hostname returns the host name reported by the kernel.
IsExist returns a boolean indicating whether its argument is known to report
that a file or directory already exists. It is satisfied by [ErrExist] as
well as some syscall errors.
This function predates [errors.Is]. It only supports errors returned by
the os package. New code should use errors.Is(err, fs.ErrExist).
IsNotExist returns a boolean indicating whether its argument is known to
report that a file or directory does not exist. It is satisfied by
[ErrNotExist] as well as some syscall errors.
This function predates [errors.Is]. It only supports errors returned by
the os package. New code should use errors.Is(err, fs.ErrNotExist).
IsPathSeparator reports whether c is a directory separator character.
IsPermission returns a boolean indicating whether its argument is known to
report that permission is denied. It is satisfied by [ErrPermission] as well
as some syscall errors.
This function predates [errors.Is]. It only supports errors returned by
the os package. New code should use errors.Is(err, fs.ErrPermission).
IsTimeout returns a boolean indicating whether its argument is known
to report that a timeout occurred.
This function predates [errors.Is], and the notion of whether an
error indicates a timeout can be ambiguous. For example, the Unix
error EWOULDBLOCK sometimes indicates a timeout and sometimes does not.
New code should use errors.Is with a value appropriate to the call
returning the error, such as [os.ErrDeadlineExceeded].
Lchown changes the numeric uid and gid of the named file.
If the file is a symbolic link, it changes the uid and gid of the link itself.
If there is an error, it will be of type [*PathError].
On Windows, it always returns the [syscall.EWINDOWS] error, wrapped
in *PathError.
Link creates newname as a hard link to the oldname file.
If there is an error, it will be of type *LinkError.
LookupEnv retrieves the value of the environment variable named
by the key. If the variable is present in the environment the
value (which may be empty) is returned and the boolean is true.
Otherwise the returned value will be empty and the boolean will
be false.
Lstat returns a [FileInfo] describing the named file.
If the file is a symbolic link, the returned FileInfo
describes the symbolic link. Lstat makes no attempt to follow the link.
If there is an error, it will be of type [*PathError].
On Windows, if the file is a reparse point that is a surrogate for another
named entity (such as a symbolic link or mounted folder), the returned
FileInfo describes the reparse point, and makes no attempt to resolve it.
Mkdir creates a new directory with the specified name and permission
bits (before umask).
If there is an error, it will be of type *PathError.
MkdirAll creates a directory named path,
along with any necessary parents, and returns nil,
or else returns an error.
The permission bits perm (before umask) are used for all
directories that MkdirAll creates.
If path is already a directory, MkdirAll does nothing
and returns nil.
MkdirTemp creates a new temporary directory in the directory dir
and returns the pathname of the new directory.
The new directory's name is generated by adding a random string to the end of pattern.
If pattern includes a "*", the random string replaces the last "*" instead.
The directory is created with mode 0o700 (before umask).
If dir is the empty string, MkdirTemp uses the default directory for temporary files, as returned by TempDir.
Multiple programs or goroutines calling MkdirTemp simultaneously will not choose the same directory.
It is the caller's responsibility to remove the directory when it is no longer needed.
NewFile returns a new File with the given file descriptor and
name. The returned value will be nil if fd is not a valid file
descriptor. On Unix systems, if the file descriptor is in
non-blocking mode, NewFile will attempt to return a pollable File
(one for which the SetDeadline methods work).
After passing it to NewFile, fd may become invalid under the same
conditions described in the comments of the Fd method, and the same
constraints apply.
NewSyscallError returns, as an error, a new [SyscallError]
with the given system call name and error details.
As a convenience, if err is nil, NewSyscallError returns nil.
Open opens the named file for reading. If successful, methods on
the returned file can be used for reading; the associated file
descriptor has mode O_RDONLY.
If there is an error, it will be of type *PathError.
OpenFile is the generalized open call; most users will use Open
or Create instead. It opens the named file with specified flag
(O_RDONLY etc.). If the file does not exist, and the O_CREATE flag
is passed, it is created with mode perm (before umask);
the containing directory must exist. If successful,
methods on the returned File can be used for I/O.
If there is an error, it will be of type *PathError.
OpenInRoot opens the file name in the directory dir.
It is equivalent to OpenRoot(dir) followed by opening the file in the root.
OpenInRoot returns an error if any component of the name
references a location outside of dir.
See [Root] for details and limitations.
OpenRoot opens the named directory.
If there is an error, it will be of type *PathError.
Pipe returns a connected pair of Files; reads from r return bytes written to w.
It returns the files and an error, if any.
ReadDir reads the named directory,
returning all its directory entries sorted by filename.
If an error occurs reading the directory,
ReadDir returns the entries it was able to read before the error,
along with the error.
ReadFile reads the named file and returns the contents.
A successful call returns err == nil, not err == EOF.
Because ReadFile reads the whole file, it does not treat an EOF from Read
as an error to be reported.
Readlink returns the destination of the named symbolic link.
If there is an error, it will be of type *PathError.
If the link destination is relative, Readlink returns the relative path
without resolving it to an absolute one.
Remove removes the named file or (empty) directory.
If there is an error, it will be of type *PathError.
RemoveAll removes path and any children it contains.
It removes everything it can but returns the first error
it encounters. If the path does not exist, RemoveAll
returns nil (no error).
If there is an error, it will be of type [*PathError].
Rename renames (moves) oldpath to newpath.
If newpath already exists and is not a directory, Rename replaces it.
If newpath already exists and is a directory, Rename returns an error.
OS-specific restrictions may apply when oldpath and newpath are in different directories.
Even within the same directory, on non-Unix platforms Rename is not an atomic operation.
If there is an error, it will be of type *LinkError.
SameFile reports whether fi1 and fi2 describe the same file.
For example, on Unix this means that the device and inode fields
of the two underlying structures are identical; on other systems
the decision may be based on the path names.
SameFile only applies to results returned by this package's [Stat].
It returns false in other cases.
Setenv sets the value of the environment variable named by the key.
It returns an error, if any.
StartProcess starts a new process with the program, arguments and attributes
specified by name, argv and attr. The argv slice will become [os.Args] in the
new process, so it normally starts with the program name.
If the calling goroutine has locked the operating system thread
with [runtime.LockOSThread] and modified any inheritable OS-level
thread state (for example, Linux or Plan 9 name spaces), the new
process will inherit the caller's thread state.
StartProcess is a low-level interface. The [os/exec] package provides
higher-level interfaces.
If there is an error, it will be of type [*PathError].
Stat returns a [FileInfo] describing the named file.
If there is an error, it will be of type [*PathError].
Symlink creates newname as a symbolic link to oldname.
On Windows, a symlink to a non-existent oldname creates a file symlink;
if oldname is later created as a directory the symlink will not work.
If there is an error, it will be of type *LinkError.
TempDir returns the default directory to use for temporary files.
On Unix systems, it returns $TMPDIR if non-empty, else /tmp.
On Windows, it uses GetTempPath, returning the first non-empty
value from %TMP%, %TEMP%, %USERPROFILE%, or the Windows directory.
On Plan 9, it returns /tmp.
The directory is neither guaranteed to exist nor have accessible
permissions.
Truncate changes the size of the named file.
If the file is a symbolic link, it changes the size of the link's target.
If there is an error, it will be of type *PathError.
Unsetenv unsets a single environment variable.
UserCacheDir returns the default root directory to use for user-specific
cached data. Users should create their own application-specific subdirectory
within this one and use that.
On Unix systems, it returns $XDG_CACHE_HOME as specified by
https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html if
non-empty, else $HOME/.cache.
On Darwin, it returns $HOME/Library/Caches.
On Windows, it returns %LocalAppData%.
On Plan 9, it returns $home/lib/cache.
If the location cannot be determined (for example, $HOME is not defined) or
the path in $XDG_CACHE_HOME is relative, then it will return an error.
UserConfigDir returns the default root directory to use for user-specific
configuration data. Users should create their own application-specific
subdirectory within this one and use that.
On Unix systems, it returns $XDG_CONFIG_HOME as specified by
https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html if
non-empty, else $HOME/.config.
On Darwin, it returns $HOME/Library/Application Support.
On Windows, it returns %AppData%.
On Plan 9, it returns $home/lib.
If the location cannot be determined (for example, $HOME is not defined) or
the path in $XDG_CONFIG_HOME is relative, then it will return an error.
UserHomeDir returns the current user's home directory.
On Unix, including macOS, it returns the $HOME environment variable.
On Windows, it returns %USERPROFILE%.
On Plan 9, it returns the $home environment variable.
If the expected variable is not set in the environment, UserHomeDir
returns either a platform-specific default value or a non-nil error.
WriteFile writes data to the named file, creating it if necessary.
If the file does not exist, WriteFile creates it with permissions perm (before umask);
otherwise WriteFile truncates it before writing, without changing permissions.
Since WriteFile requires multiple system calls to complete, a failure mid-operation
can leave the file in a partially written state.
Package-Level Variables (total 14)
Args hold the command-line arguments, starting with the program name.
Portable analogs of some common system call errors.
Errors returned from this package may be tested against these errors
with [errors.Is].
Portable analogs of some common system call errors.
Errors returned from this package may be tested against these errors
with [errors.Is].
Portable analogs of some common system call errors.
Errors returned from this package may be tested against these errors
with [errors.Is].
ErrInvalid indicates an invalid argument.
Methods on File will return this error when the receiver is nil.
Portable analogs of some common system call errors.
Errors returned from this package may be tested against these errors
with [errors.Is].
Portable analogs of some common system call errors.
Errors returned from this package may be tested against these errors
with [errors.Is].
Portable analogs of some common system call errors.
Errors returned from this package may be tested against these errors
with [errors.Is].
ErrProcessDone indicates a [Process] has finished.
The only signal values guaranteed to be present in the os package on all
systems are os.Interrupt (send the process an interrupt) and os.Kill (force
the process to exit). On Windows, sending os.Interrupt to a process with
os.Process.Signal is not implemented; it will return an error instead of
sending a signal.
The only signal values guaranteed to be present in the os package on all
systems are os.Interrupt (send the process an interrupt) and os.Kill (force
the process to exit). On Windows, sending os.Interrupt to a process with
os.Process.Signal is not implemented; it will return an error instead of
sending a signal.
Stdin, Stdout, and Stderr are open Files pointing to the standard input,
standard output, and standard error file descriptors.
Note that the Go runtime writes to standard error for panics and crashes;
closing Stderr may cause those messages to go elsewhere, perhaps
to a file opened later.
Stdin, Stdout, and Stderr are open Files pointing to the standard input,
standard output, and standard error file descriptors.
Note that the Go runtime writes to standard error for panics and crashes;
closing Stderr may cause those messages to go elsewhere, perhaps
to a file opened later.
Stdin, Stdout, and Stderr are open Files pointing to the standard input,
standard output, and standard error file descriptors.
Note that the Go runtime writes to standard error for panics and crashes;
closing Stderr may cause those messages to go elsewhere, perhaps
to a file opened later.
Package-Level Constants (total 29)
DevNull is the name of the operating system's “null device.”
On Unix-like systems, it is "/dev/null"; on Windows, "NUL".
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The single letters are the abbreviations
used by the String method's formatting.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
The defined file mode bits are the most significant bits of the [FileMode].
The nine least-significant bits are the standard Unix rwxrwxrwx permissions.
The values of these bits should be considered part of the public API and
may be used in wire protocols or disk representations: they must not be
changed, although new bits might be added.
Mask for the type bits. For regular files, none will be set.
The remaining values may be or'ed in to control behavior.
Flags to OpenFile wrapping those of the underlying system. Not all
flags may be implemented on a given system.
Flags to OpenFile wrapping those of the underlying system. Not all
flags may be implemented on a given system.
Exactly one of O_RDONLY, O_WRONLY, or O_RDWR must be specified.
Flags to OpenFile wrapping those of the underlying system. Not all
flags may be implemented on a given system.
Flags to OpenFile wrapping those of the underlying system. Not all
flags may be implemented on a given system.
Flags to OpenFile wrapping those of the underlying system. Not all
flags may be implemented on a given system.
Flags to OpenFile wrapping those of the underlying system. Not all
flags may be implemented on a given system.
Seek whence values.
Deprecated: Use io.SeekStart, io.SeekCurrent, and io.SeekEnd.
Seek whence values.
Deprecated: Use io.SeekStart, io.SeekCurrent, and io.SeekEnd.
Seek whence values.
Deprecated: Use io.SeekStart, io.SeekCurrent, and io.SeekEnd.
The pages are generated with Goldsv0.7.3-preview. (GOOS=linux GOARCH=amd64)
Golds is a Go 101 project developed by Tapir Liu.
PR and bug reports are welcome and can be submitted to the issue list.
Please follow @zigo_101 (reachable from the left QR code) to get the latest news of Golds.
