dup3_test.go

Documentation: golang.org/x/sys/unix

     1  // Copyright 2023 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  //go:build freebsd || linux || netbsd || openbsd
     6  
     7  package unix_test
     8  
     9  import (
    10  	"os"
    11  	"path/filepath"
    12  	"runtime"
    13  	"testing"
    14  
    15  	"golang.org/x/sys/unix"
    16  )
    17  
    18  func TestDup3(t *testing.T) {
    19  	tempFile, err := os.Create(filepath.Join(t.TempDir(), "TestDup"))
    20  	if err != nil {
    21  		t.Fatal(err)
    22  	}
    23  	defer tempFile.Close()
    24  	oldFd := int(tempFile.Fd())
    25  
    26  	// On NetBSD, it is not an error if oldFd == newFd
    27  	if runtime.GOOS != "netbsd" {
    28  		if got, want := unix.Dup3(oldFd, oldFd, 0), unix.EINVAL; got != want {
    29  			t.Fatalf("Dup3: expected err %v, got %v", want, got)
    30  		}
    31  	}
    32  
    33  	// Create and reserve a file descriptor.
    34  	// Dup3 automatically closes it before reusing it.
    35  	nullFile, err := os.Open("/dev/null")
    36  	if err != nil {
    37  		t.Fatalf("Open failed: %v", err)
    38  	}
    39  	defer nullFile.Close()
    40  	newFd := int(nullFile.Fd())
    41  
    42  	err = unix.Dup3(oldFd, newFd, 0)
    43  	if err != nil {
    44  		t.Fatalf("Dup3: %v", err)
    45  	}
    46  
    47  	b1 := []byte("Test123")
    48  	b2 := make([]byte, 7)
    49  	_, err = unix.Write(newFd, b1)
    50  	if err != nil {
    51  		t.Fatalf("Write to Dup3 fd failed: %v", err)
    52  	}
    53  	_, err = unix.Seek(oldFd, 0, 0)
    54  	if err != nil {
    55  		t.Fatalf("Seek failed: %v", err)
    56  	}
    57  	_, err = unix.Read(oldFd, b2)
    58  	if err != nil {
    59  		t.Fatalf("Read back failed: %v", err)
    60  	}
    61  	if string(b1) != string(b2) {
    62  		t.Errorf("Dup3: read %q from file, want %q", string(b2), string(b1))
    63  	}
    64  }
    65
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