undocker/main.go

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package main
import (
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"errors"
"fmt"
"io"
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"os"
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"git.sr.ht/~motiejus/code/undocker/rootfs"
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goflags "github.com/jessevdk/go-flags"
)
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const _description = "Flatten a docker container image to a tarball"
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func main() {
parser := goflags.NewParser(newCommand(), goflags.Default)
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_, err := parser.Parse()
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if err != nil {
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os.Exit(1)
}
os.Exit(0)
}
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// command implements go-flags.Command
type command struct {
flattener func(io.ReadSeeker, io.Writer) error
Stdout io.Writer
PositionalArgs struct {
Infile goflags.Filename `long:"infile" description:"Input tarball"`
Outfile string `long:"outfile" description:"Output path, stdout is '-'"`
} `positional-args:"yes" required:"yes"`
}
// newCommand creates a new Command struct
func newCommand() *command {
return &command{
flattener: rootfs.Flatten,
Stdout: os.Stdout,
}
}
// Execute executes rootfs Command
func (c *command) Execute(args []string) (err error) {
if len(args) != 0 {
return errors.New("too many args")
}
rd, err := os.Open(string(c.PositionalArgs.Infile))
if err != nil {
return err
}
defer func() {
err1 := rd.Close()
if err == nil {
err = err1
}
}()
var out io.Writer
if fname := string(c.PositionalArgs.Outfile); fname == "-" {
out = c.Stdout
} else {
outf, err := os.Create(fname)
if err != nil {
return fmt.Errorf("create: %w", err)
}
defer func() {
err1 := outf.Close()
if err == nil {
err = err1
}
}()
out = outf
}
return c.flattener(rd, out)
}