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feat: add --no-stdin flag to container attach #4176

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Merged
merged 1 commit into from
May 13, 2025
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feat: add --no-stdin flag to container attach #4176

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14 changes: 13 additions & 1 deletion cmd/nerdctl/container/container_attach.go
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Original file line number Diff line number Diff line change
Expand Up @@ -17,6 +17,8 @@
package container

import (
"io"

"github.com/spf13/cobra"

containerd "github.com/containerd/containerd/v2/client"
Expand Down Expand Up @@ -56,6 +58,7 @@ Caveats:
SilenceErrors: true,
}
cmd.Flags().String("detach-keys", consoleutil.DefaultDetachKeys, "Override the default detach keys")
cmd.Flags().Bool("no-stdin", false, "Do not attach STDIN")
return cmd
}

Expand All @@ -68,9 +71,18 @@ func attachOptions(cmd *cobra.Command) (types.ContainerAttachOptions, error) {
if err != nil {
return types.ContainerAttachOptions{}, err
}
noStdin, err := cmd.Flags().GetBool("no-stdin")
if err != nil {
return types.ContainerAttachOptions{}, err
}

var stdin io.Reader
if !noStdin {
stdin = cmd.InOrStdin()
}
return types.ContainerAttachOptions{
GOptions: globalOptions,
Stdin: cmd.InOrStdin(),
Stdin: stdin,
Stdout: cmd.OutOrStdout(),
Stderr: cmd.ErrOrStderr(),
DetachKeys: detachKeys,
Expand Down
41 changes: 41 additions & 0 deletions cmd/nerdctl/container/container_attach_linux_test.go
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Expand Up @@ -211,3 +211,44 @@ func TestAttachForAutoRemovedContainer(t *testing.T) {

testCase.Run(t)
}

func TestAttachNoStdin(t *testing.T) {
testCase := nerdtest.Setup()

testCase.Cleanup = func(data test.Data, helpers test.Helpers) {
helpers.Anyhow("rm", "-f", data.Identifier())
}

testCase.Setup = func(data test.Data, helpers test.Helpers) {
cmd := helpers.Command("run", "-it", "--detach-keys=ctrl-p,ctrl-q", "--name", data.Identifier(),
testutil.CommonImage, "sleep", "5")
cmd.WithPseudoTTY()
cmd.Feed(bytes.NewReader([]byte{16, 17})) // Ctrl-p, Ctrl-q to detach (https://en.wikipedia.org/wiki/C0_and_C1_control_codes)
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@apostasie apostasie May 9, 2025 •
edited
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@subashkotha let's test my hypothesis that there is a bug in logging.

So, instead of sending cmd.Feed(bytes.NewReader([]byte{16, 17})) after one second, instead do your logs / wait on ready BEFORE sending the escape sequence.

eg:

cmd.Feeder(func()io.Reader{

for {
				out := helpers.Capture("logs", data.Identifier())
				if strings.Contains(out, "ready") {
					break
				}
}

return bytes.NewReader([]byte{16, 17})

}
)

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Pseudo-code ^ just add back the sleep and make this proper - thanks a lot! :-)

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Thanks, let me try this out.

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Checking logs during setup isn't reliable since the container isn't running yet. I’ve updated the test to avoid relying on logs altogether, especially given the known issue: #4233.

Instead, we now attach with --no-stdin, send input like xyz, and simply assert that xyz does not appear in the logs after attach.

cmd.Run(&test.Expected{
ExitCode: 0,
Output: func(stdout string, info string, t *testing.T) {
assert.Assert(t, strings.Contains(helpers.Capture("inspect", "--format", "{{.State.Running}}", data.Identifier()), "true"))
},
})
}

testCase.Command = func(data test.Data, helpers test.Helpers) test.TestableCommand {
cmd := helpers.Command("attach", "--no-stdin", data.Identifier())
cmd.WithPseudoTTY()
cmd.Feed(strings.NewReader("should-not-appear\n"))
cmd.Feed(bytes.NewReader([]byte{16, 17}))
return cmd
}

testCase.Expected = func(data test.Data, helpers test.Helpers) *test.Expected {
return &test.Expected{
ExitCode: 0, // Since it's a normal exit and not detach.
Output: func(stdout string, info string, t *testing.T) {
logs := helpers.Capture("logs", data.Identifier())
assert.Assert(t, !strings.Contains(logs, "should-not-appear"))
},
}
}

testCase.Run(t)
}
3 changes: 2 additions & 1 deletion docs/command-reference.md
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Expand Up @@ -686,8 +686,9 @@ Usage: `nerdctl attach CONTAINER`
Flags:

- :whale: `--detach-keys`: Override the default detach keys
- :whale: `--no-stdin`: Do not attach STDIN

Unimplemented `docker attach` flags: `--no-stdin`, `--sig-proxy`
Unimplemented `docker attach` flags: `--sig-proxy`

### :whale: nerdctl container prune

Expand Down
10 changes: 7 additions & 3 deletions pkg/cmd/container/attach.go
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Expand Up @@ -20,6 +20,7 @@ import (
"context"
"errors"
"fmt"
"io"

"golang.org/x/term"

Expand Down Expand Up @@ -114,9 +115,12 @@ func Attach(ctx context.Context, client *containerd.Client, req string, options
}
io.Cancel()
}
in, err := consoleutil.NewDetachableStdin(con, options.DetachKeys, closer)
if err != nil {
return err
var in io.Reader
if options.Stdin != nil {
in, err = consoleutil.NewDetachableStdin(con, options.DetachKeys, closer)
if err != nil {
return err
}
}
opt = cio.WithStreams(in, con, nil)
} else {
Expand Down
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