github.com/vmware/govmomi@v0.51.0/cli/datastore/tail.go (about)

     1  // © Broadcom. All Rights Reserved.
     2  // The term “Broadcom” refers to Broadcom Inc. and/or its subsidiaries.
     3  // SPDX-License-Identifier: Apache-2.0
     4  
     5  package datastore
     6  
     7  import (
     8  	"context"
     9  	"flag"
    10  	"io"
    11  	"os"
    12  	"time"
    13  
    14  	"github.com/vmware/govmomi/cli"
    15  	"github.com/vmware/govmomi/cli/flags"
    16  )
    17  
    18  type tail struct {
    19  	*flags.DatastoreFlag
    20  	*flags.HostSystemFlag
    21  
    22  	count  int64
    23  	lines  int
    24  	follow bool
    25  }
    26  
    27  func init() {
    28  	cli.Register("datastore.tail", &tail{})
    29  }
    30  
    31  func (cmd *tail) Register(ctx context.Context, f *flag.FlagSet) {
    32  	cmd.DatastoreFlag, ctx = flags.NewDatastoreFlag(ctx)
    33  	cmd.DatastoreFlag.Register(ctx, f)
    34  
    35  	cmd.HostSystemFlag, ctx = flags.NewHostSystemFlag(ctx)
    36  	cmd.HostSystemFlag.Register(ctx, f)
    37  
    38  	f.Int64Var(&cmd.count, "c", -1, "Output the last NUM bytes")
    39  	f.IntVar(&cmd.lines, "n", 10, "Output the last NUM lines")
    40  	f.BoolVar(&cmd.follow, "f", false, "Output appended data as the file grows")
    41  }
    42  
    43  func (cmd *tail) Description() string {
    44  	return `Output the last part of datastore files.
    45  
    46  Examples:
    47    govc datastore.tail -n 100 vm-name/vmware.log
    48    govc datastore.tail -n 0 -f vm-name/vmware.log`
    49  }
    50  
    51  func (cmd *tail) Process(ctx context.Context) error {
    52  	if err := cmd.DatastoreFlag.Process(ctx); err != nil {
    53  		return err
    54  	}
    55  	if err := cmd.HostSystemFlag.Process(ctx); err != nil {
    56  		return err
    57  	}
    58  	return nil
    59  }
    60  
    61  func (cmd *tail) Usage() string {
    62  	return "PATH"
    63  }
    64  
    65  func (cmd *tail) Run(ctx context.Context, f *flag.FlagSet) error {
    66  	if f.NArg() != 1 {
    67  		return flag.ErrHelp
    68  	}
    69  
    70  	p := cmd.Args(f.Args())[0]
    71  
    72  	ds, err := cmd.Datastore()
    73  	if err != nil {
    74  		return err
    75  	}
    76  
    77  	h, err := cmd.HostSystemIfSpecified()
    78  	if err != nil {
    79  		return err
    80  	}
    81  
    82  	if h != nil {
    83  		ctx = ds.HostContext(ctx, h)
    84  	}
    85  
    86  	file, err := ds.Open(ctx, p.Path)
    87  	if err != nil {
    88  		return err
    89  	}
    90  
    91  	var reader io.ReadCloser = file
    92  
    93  	var offset int64
    94  
    95  	if cmd.count >= 0 {
    96  		info, serr := file.Stat()
    97  		if serr != nil {
    98  			return serr
    99  		}
   100  
   101  		if info.Size() > cmd.count {
   102  			offset = info.Size() - cmd.count
   103  
   104  			_, err = file.Seek(offset, io.SeekStart)
   105  			if err != nil {
   106  				return err
   107  			}
   108  		}
   109  	} else if cmd.lines >= 0 {
   110  		err = file.Tail(cmd.lines)
   111  		if err != nil {
   112  			return err
   113  		}
   114  	}
   115  
   116  	if cmd.follow {
   117  		reader = file.Follow(time.Second)
   118  	}
   119  
   120  	_, err = io.Copy(os.Stdout, reader)
   121  
   122  	_ = reader.Close()
   123  
   124  	return err
   125  }