113 lines
2.1 KiB
Go
113 lines
2.1 KiB
Go
// Package main is a simple command-line application on top of rootfs.Flatten.
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package main
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import (
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"flag"
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"fmt"
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"io"
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"os"
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"path/filepath"
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"runtime"
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"git.sr.ht/~motiejus/undocker/rootfs"
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)
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var Version = "unknown"
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var VersionHash = "unknown"
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const _usage = `Usage:
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%s [OPTION]... <infile> <outfile>
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Flatten a Docker container image to a root file system.
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Arguments:
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<infile> Input Docker container. Tarball.
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<outfile> Output tarball, the root file system. '-' is stdout.
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Options:
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--prefix=<prefix> prefix all destination files with a given string.
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undocker %s (%s)
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Built with %s
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`
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func usage(pre string, out io.Writer) {
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fmt.Fprintf(out, pre+_usage,
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filepath.Base(os.Args[0]),
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Version,
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VersionHash,
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runtime.Version(),
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)
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}
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func usageErr(pre string) {
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usage(pre, os.Stderr)
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os.Exit(2)
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}
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func main() {
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runtime.GOMAXPROCS(1) // no need to create that many threads
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var filePrefix string
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fs := flag.NewFlagSet("undocker", flag.ExitOnError)
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fs.Usage = func() { usageErr("") }
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fs.StringVar(&filePrefix, "prefix", "", "prefix files in the tarball")
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if len(os.Args) == 1 {
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usageErr("")
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}
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_ = fs.Parse(os.Args[1:]) // ExitOnError captures it
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args := fs.Args()
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if len(args) != 2 {
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usageErr("invalid number of arguments\n")
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}
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c := &command{flattener: rootfs.Flatten, Stdout: os.Stdout}
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if err := c.execute(args[0], args[1], filePrefix); err != nil {
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fmt.Printf("Error: %v\n", err)
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os.Exit(1)
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}
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os.Exit(0)
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}
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type command struct {
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flattener func(io.ReadSeeker, io.Writer, ...rootfs.Option) error
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Stdout io.Writer
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}
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func (c *command) execute(infile, outfile, filePrefix string) (_err error) {
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rd, err := os.Open(infile)
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if err != nil {
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return err
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}
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defer func() {
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err := rd.Close()
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if _err == nil {
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_err = err
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}
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}()
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var out io.Writer
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if outfile == "-" {
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out = c.Stdout
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} else {
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outf, err := os.Create(outfile)
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if err != nil {
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return fmt.Errorf("create: %w", err)
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}
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defer func() {
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err := outf.Close()
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if _err != nil {
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os.Remove(outfile)
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} else {
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_err = err
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}
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}()
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out = outf
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}
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return c.flattener(rd, out, rootfs.WithFilePrefix(filePrefix))
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}
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