github.com/stolowski/snapd@v0.0.0-20210407085831-115137ce5a22/osutil/sys_linux_test.go (about)

     1  // -*- Mode: Go; indent-tabs-mode: t -*-
     2  
     3  /*
     4   * Copyright (C) 2018 Canonical Ltd
     5   *
     6   * This program is free software: you can redistribute it and/or modify
     7   * it under the terms of the GNU General Public License version 3 as
     8   * published by the Free Software Foundation.
     9   *
    10   * This program is distributed in the hope that it will be useful,
    11   * but WITHOUT ANY WARRANTY; without even the implied warranty of
    12   * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    13   * GNU General Public License for more details.
    14   *
    15   * You should have received a copy of the GNU General Public License
    16   * along with this program.  If not, see <http://www.gnu.org/licenses/>.
    17   *
    18   */
    19  
    20  package osutil_test
    21  
    22  import (
    23  	"os"
    24  	"path/filepath"
    25  	"syscall"
    26  
    27  	. "gopkg.in/check.v1"
    28  
    29  	"github.com/snapcore/snapd/osutil"
    30  )
    31  
    32  type sysSuite struct{}
    33  
    34  var _ = Suite(&sysSuite{})
    35  
    36  func (s *sysSuite) TestSymlinkatAndReadlinkat(c *C) {
    37  	// Create and open a temporary directory.
    38  	d := c.MkDir()
    39  	fd, err := syscall.Open(d, syscall.O_DIRECTORY, 0)
    40  	c.Assert(err, IsNil)
    41  	defer syscall.Close(fd)
    42  
    43  	// Create a symlink relative to the directory file descriptor.
    44  	err = osutil.Symlinkat("target", fd, "linkpath")
    45  	c.Assert(err, IsNil)
    46  
    47  	// Ensure that the created file is a symlink.
    48  	fname := filepath.Join(d, "linkpath")
    49  	fi, err := os.Lstat(fname)
    50  	c.Assert(err, IsNil)
    51  	c.Assert(fi.Name(), Equals, "linkpath")
    52  	c.Assert(fi.Mode()&os.ModeSymlink, Equals, os.ModeSymlink)
    53  
    54  	// Ensure that the symlink target is correct.
    55  	target, err := os.Readlink(fname)
    56  	c.Assert(err, IsNil)
    57  	c.Assert(target, Equals, "target")
    58  
    59  	// Use readlinkat with a buffer that fits only part of the target path.
    60  	buf := make([]byte, 2)
    61  	n, err := osutil.Readlinkat(fd, "linkpath", buf)
    62  	c.Assert(err, IsNil)
    63  	c.Assert(n, Equals, 2)
    64  	c.Assert(buf, DeepEquals, []byte{'t', 'a'})
    65  
    66  	// Use a buffer that fits all of the target path.
    67  	buf = make([]byte, 100)
    68  	n, err = osutil.Readlinkat(fd, "linkpath", buf)
    69  	c.Assert(err, IsNil)
    70  	c.Assert(n, Equals, len("target"))
    71  	c.Assert(buf[:n], DeepEquals, []byte{'t', 'a', 'r', 'g', 'e', 't'})
    72  }