86 lines
1.6 KiB
Go
86 lines
1.6 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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"errors"
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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.jakstys.lt/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 <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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undocker %s (%s)
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Built with %s
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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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if len(os.Args) != 3 {
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fmt.Fprintf(os.Stderr, _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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os.Exit(1)
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}
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c := &command{flattener: rootfs.Flatten, Stdout: os.Stdout}
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if err := c.execute(os.Args[1], os.Args[2]); err != nil {
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fmt.Sprintf(os.Stderr, "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) error
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Stdout io.Writer
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}
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func (c *command) execute(infile string, outfile 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 = errors.Join(_err, rd.Close())
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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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if _err != nil {
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_err = errors.Join(_err, os.Remove(outfile))
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} else {
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_err = errors.Join(_err, outf.Close())
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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)
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}
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