package os

Import Path
	os (on go.dev)

Dependency Relation
	imports 15 packages, and imported by 8 packages


Involved Source Files

	      dir.go
	      dir_darwin.go
	      endian_little.go
	      env.go
	      error.go
	      error_errno.go
	      error_posix.go
	      exec.go
	      exec_posix.go
	      exec_unix.go
	      executable.go
	      executable_darwin.go
	
		Package os provides a platform-independent interface to operating system
		functionality. The design is Unix-like, although the error handling is
		Go-like; failing calls return values of type error rather than error numbers.
		Often, more information is available within the error. For example,
		if a call that takes a file name fails, such as Open or Stat, the error
		will include the failing file name when printed and will be of type
		*PathError, which may be unpacked for more information.

		The os interface is intended to be uniform across all operating systems.
		Features not generally available appear in the system-specific package syscall.

		Here is a simple example, opening a file and reading some of it.

		file, err := os.Open("file.go") // For read access.
		if err != nil {
			log.Fatal(err)
		}

		If the open fails, the error string will be self-explanatory, like

		open file.go: no such file or directory

		The file's data can then be read into a slice of bytes. Read and
		Write take their byte counts from the length of the argument slice.

		data := make([]byte, 100)
		count, err := file.Read(data)
		if err != nil {
			log.Fatal(err)
		}
		fmt.Printf("read %d bytes: %q\n", count, data[:count])

		Note: The maximum number of concurrent operations on a File may be limited by
		the OS or the system. The number should be high, but exceeding it may degrade
		performance or cause other issues.

	      file_posix.go
	      file_unix.go
	      getwd.go
	      path.go
	      path_unix.go
	      pipe_bsd.go
	      proc.go
	      rawconn.go
	      readfrom_stub.go
	      removeall_at.go
	      stat.go
	      stat_darwin.go
	      stat_unix.go
	      sticky_bsd.go
	      str.go
	      sys.go
	      sys_bsd.go
	      sys_unix.go
	      tempfile.go
	      types.go
	      types_unix.go
	      wait_unimp.go


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 (
			"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()) // 0400, 0777, 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() {
			filename := "a-nonexistent-file"
			if _, err := os.Stat(filename); os.IsNotExist(err) {
				fmt.Println("file does not exist")
			}
		}

	
		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"
			"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, 0755)
			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 (
			"os"
		)
		
		func main() {
			os.Setenv("TMPDIR", "/my/tmp")
			defer os.Unsetenv("TMPDIR")
		}

	
		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 22, in which 11 are exported)


	/* sort exporteds by:  |  */
	
		A DirEntry is an entry read from a directory
		(using the ReadDir function or a File's ReadDir method).


	
		File represents an open file descriptor.

		
			
		
			
				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 SetDeadline, any pending I/O operations will
				be canceled and return immediately with an 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 SetDeadline
				methods to stop working.
				Because file descriptors can be reused, the returned file descriptor may
				only be closed through the 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.

			
				Read reads up to len(b) bytes from the File.
				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.

				If f is a directory, the behavior of Seek varies by operating
				system; you can seek to the beginning of the directory on Unix-like
				operating systems, but not on Windows.

			
				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 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.

			
		
			*T : github.com/neo4j/neo4j-go-driver/v4/neo4j.DatabaseInfo
			*T : io.Closer
			*T : io.ReadCloser
			*T : io.Reader
			*T : io.ReaderAt
			*T : io.ReaderFrom
			*T : io.ReadSeekCloser
			*T : io.ReadSeeker
			*T : io.ReadWriteCloser
			*T : io.ReadWriter
			*T : io.ReadWriteSeeker
			*T : io.Seeker
			*T : io.StringWriter
			*T : io.WriteCloser
			*T : io.Writer
			*T : io.WriterAt
			*T : io.WriteSeeker
			*T : io/fs.File
			*T : io/fs.ReadDirFile
			*T : 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 Pipe() (r *File, w *File, err error)
			func Pipe() (r *File, w *File, err error)
			func net.(*TCPListener).File() (f *File, err error)
			func net.(*UnixListener).File() (f *File, err 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)
			
		
			  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.


	
		LinkError records an error during a link or symlink or rename
		system call and the paths that caused it.

		
			Err error
			New string
			Old string
			Op string
		
			(*T) Error() string
			(*T) Unwrap() error
		
			*T : error


	
		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.

			
				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.

		
			Pid int
			
		
			
				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 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.

			
				Pid returns the process id of the exited process.

			(*T) 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.

			
		
			*T : fmt.Stringer
			
		
			func (*Process).Wait() (*ProcessState, 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

			( T) String() string
		
			 syscall.Signal
		
			 T : fmt.Stringer
			
		
			func (*Process).Signal(sig Signal) error
			
		
			  var Interrupt
			  var Kill


	
		SyscallError records an error from a specific system call.

		
			Err error
			Syscall string
		
			(*T) Error() string
			
				Timeout reports whether this error represents a timeout.

			(*T) Unwrap() error
		
			*T : error
			


	


Package-Level Functions (total 117, in which 60 are exported)


	
		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 0200 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 0400 for a read-only
		file and 0600 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.

		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.


	
		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 0666
		(before umask). If successful, methods on the returned File can
		be used for I/O; the associated file descriptor has mode O_RDWR.
		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 "*".
		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. DirFS is therefore not a general substitute for a chroot-style security
		mechanism when the directory tree contains arbitrary content.


	
		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.


	
		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 a rooted 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.


	
		Hostname returns the host name reported by the kernel.


	
		IsExist returns a boolean indicating whether the error 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, os.ErrExist).


	
		IsNotExist returns a boolean indicating whether the error 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, os.ErrNotExist).


	
		IsPathSeparator reports whether c is a directory separator character.


	
		IsPermission returns a boolean indicating whether the error 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, os.ErrPermission).


	
		IsTimeout returns a boolean indicating whether the error 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.


	
		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.


	
		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.
		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). If successful,
		methods on the returned File can be used for I/O.
		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.


	
		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.
		OS-specific restrictions may apply when oldpath and newpath are in different directories.
		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.


	
		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),
		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),
		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.


	
		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.


	


Package-Level Variables (total 22, in which 14 are exported)


	
		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 39, in which 29 are exported)


	
		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.


	
		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.


	const PathListSeparator = 58 // OS-specific path list separator
	const PathSeparator = 47 // OS-specific path separator
	
		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.