{"record":{"id":"c4986f30ebe5f6f2","repo":"cloudflare/cloudflared","slug":"error-copying-stderr-from-s-to-file-s-w","errorCode":null,"errorMessage":"error copying stderr from %s to file %s: %w","messagePattern":"error copying stderr from (.+?) to file (.+?): %w","errorType":"exception","errorClass":null,"httpStatus":null,"severity":"error","filePath":"diagnostic/log_collector_utils.go","lineNumber":50,"sourceCode":"\t\t\t\"error running command '%s': %w\",\n\t\t\tcommand.String(),\n\t\t\terr,\n\t\t)\n\t}\n\n\t_, err = io.Copy(outputHandle, stdoutReader)\n\tif err != nil {\n\t\treturn nil, fmt.Errorf(\n\t\t\t\"error copying stdout from %s to file %s: %w\",\n\t\t\tcommand.String(),\n\t\t\toutputHandle.Name(),\n\t\t\terr,\n\t\t)\n\t}\n\n\t_, err = io.Copy(outputHandle, stderrReader)\n\tif err != nil {\n\t\treturn nil, fmt.Errorf(\n\t\t\t\"error copying stderr from %s to file %s: %w\",\n\t\t\tcommand.String(),\n\t\t\toutputHandle.Name(),\n\t\t\terr,\n\t\t)\n\t}\n\n\tif err := command.Wait(); err != nil {\n\t\treturn nil, fmt.Errorf(\n\t\t\t\"error waiting from command '%s': %w\",\n\t\t\tcommand.String(),\n\t\t\terr,\n\t\t)\n\t}\n\n\treturn NewLogInformation(outputHandle.Name(), true, false), nil\n}\n","sourceCodeStart":32,"sourceCodeEnd":68,"githubUrl":"https://github.com/cloudflare/cloudflared/blob/2253eeeb25a44a713a4b60b8ba1e1b3f377d1a0f/diagnostic/log_collector_utils.go#L32-L68","documentation":"PipeCommandOutputToFile runs a diagnostic command and streams its stderr into a file. This error wraps any failure of io.Copy from the command's stderr pipe to the output file, with the command and target file names for context.","triggerScenarios":"io.Copy(outputHandle, stderrReader) fails mid-stream: disk full while writing the temp log, output file closed/invalid, or read error on the command's stderr pipe (command crashed, pipe broken).","commonSituations":"cloudflared diagnostic log collection on a host with full disk or read-only /tmp; journalctl/other command killed mid-read.","solutions":["Check free disk space in os.TempDir() target filesystem","Re-run the diagnostic collection command","Inspect the wrapped error to see whether the read (command) or write (file) side failed"],"exampleFix":null,"handlingStrategy":"try-catch","validationCode":"if fi, err := os.Stat(tempDir); err != nil || !fi.IsDir() { /* pick writable temp dir */ }","typeGuard":null,"tryCatchPattern":"collector, err := diagnostic.PipeCommandOutputToFile(ctx, fs, cmd, output)\nif err != nil {\n\tvar perr *fs.PathError\n\tif errors.As(err, &perr) { /* disk/permission issue on output file */ }\n\treturn fmt.Errorf(\"log collection failed: %w\", err)\n}","preventionTips":["Monitor free disk space where diagnostics write","Ensure temp dir is writable by the running user","Handle partial log files gracefully on collection failure"],"tags":["io","diagnostics","log-collection"],"backgroundTag":"file-write-failed","analyzedSha":"2253eeeb25a44a713a4b60b8ba1e1b3f377d1a0f","analyzedAt":"2026-09-06T04:14:33.757Z","contentChangedAt":"2026-09-06T04:14:33.757Z","schemaVersion":2},"datasetVersion":"2026-09-14T00:17:10.932Z"}