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Source file src/os/file_posix.go

     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4	
     5	// +build darwin dragonfly freebsd linux nacl netbsd openbsd solaris windows
     6	
     7	package os
     8	
     9	import (
    10		"syscall"
    11		"time"
    12	)
    13	
    14	func sigpipe() // implemented in package runtime
    15	
    16	// Readlink returns the destination of the named symbolic link.
    17	// If there is an error, it will be of type *PathError.
    18	func Readlink(name string) (string, error) {
    19		for len := 128; ; len *= 2 {
    20			b := make([]byte, len)
    21			n, e := fixCount(syscall.Readlink(name, b))
    22			if e != nil {
    23				return "", &PathError{"readlink", name, e}
    24			}
    25			if n < len {
    26				return string(b[0:n]), nil
    27			}
    28		}
    29	}
    30	
    31	// syscallMode returns the syscall-specific mode bits from Go's portable mode bits.
    32	func syscallMode(i FileMode) (o uint32) {
    33		o |= uint32(i.Perm())
    34		if i&ModeSetuid != 0 {
    35			o |= syscall.S_ISUID
    36		}
    37		if i&ModeSetgid != 0 {
    38			o |= syscall.S_ISGID
    39		}
    40		if i&ModeSticky != 0 {
    41			o |= syscall.S_ISVTX
    42		}
    43		// No mapping for Go's ModeTemporary (plan9 only).
    44		return
    45	}
    46	
    47	// Chmod changes the mode of the named file to mode.
    48	// If the file is a symbolic link, it changes the mode of the link's target.
    49	// If there is an error, it will be of type *PathError.
    50	func Chmod(name string, mode FileMode) error {
    51		if e := syscall.Chmod(name, syscallMode(mode)); e != nil {
    52			return &PathError{"chmod", name, e}
    53		}
    54		return nil
    55	}
    56	
    57	// Chmod changes the mode of the file to mode.
    58	// If there is an error, it will be of type *PathError.
    59	func (f *File) Chmod(mode FileMode) error {
    60		if f == nil {
    61			return ErrInvalid
    62		}
    63		if e := syscall.Fchmod(f.fd, syscallMode(mode)); e != nil {
    64			return &PathError{"chmod", f.name, e}
    65		}
    66		return nil
    67	}
    68	
    69	// Chown changes the numeric uid and gid of the named file.
    70	// If the file is a symbolic link, it changes the uid and gid of the link's target.
    71	// If there is an error, it will be of type *PathError.
    72	func Chown(name string, uid, gid int) error {
    73		if e := syscall.Chown(name, uid, gid); e != nil {
    74			return &PathError{"chown", name, e}
    75		}
    76		return nil
    77	}
    78	
    79	// Lchown changes the numeric uid and gid of the named file.
    80	// If the file is a symbolic link, it changes the uid and gid of the link itself.
    81	// If there is an error, it will be of type *PathError.
    82	func Lchown(name string, uid, gid int) error {
    83		if e := syscall.Lchown(name, uid, gid); e != nil {
    84			return &PathError{"lchown", name, e}
    85		}
    86		return nil
    87	}
    88	
    89	// Chown changes the numeric uid and gid of the named file.
    90	// If there is an error, it will be of type *PathError.
    91	func (f *File) Chown(uid, gid int) error {
    92		if f == nil {
    93			return ErrInvalid
    94		}
    95		if e := syscall.Fchown(f.fd, uid, gid); e != nil {
    96			return &PathError{"chown", f.name, e}
    97		}
    98		return nil
    99	}
   100	
   101	// Truncate changes the size of the file.
   102	// It does not change the I/O offset.
   103	// If there is an error, it will be of type *PathError.
   104	func (f *File) Truncate(size int64) error {
   105		if f == nil {
   106			return ErrInvalid
   107		}
   108		if e := syscall.Ftruncate(f.fd, size); e != nil {
   109			return &PathError{"truncate", f.name, e}
   110		}
   111		return nil
   112	}
   113	
   114	// Sync commits the current contents of the file to stable storage.
   115	// Typically, this means flushing the file system's in-memory copy
   116	// of recently written data to disk.
   117	func (f *File) Sync() error {
   118		if f == nil {
   119			return ErrInvalid
   120		}
   121		if e := syscall.Fsync(f.fd); e != nil {
   122			return NewSyscallError("fsync", e)
   123		}
   124		return nil
   125	}
   126	
   127	// Chtimes changes the access and modification times of the named
   128	// file, similar to the Unix utime() or utimes() functions.
   129	//
   130	// The underlying filesystem may truncate or round the values to a
   131	// less precise time unit.
   132	// If there is an error, it will be of type *PathError.
   133	func Chtimes(name string, atime time.Time, mtime time.Time) error {
   134		var utimes [2]syscall.Timespec
   135		utimes[0] = syscall.NsecToTimespec(atime.UnixNano())
   136		utimes[1] = syscall.NsecToTimespec(mtime.UnixNano())
   137		if e := syscall.UtimesNano(name, utimes[0:]); e != nil {
   138			return &PathError{"chtimes", name, e}
   139		}
   140		return nil
   141	}
   142	

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