bazelbuild/bazel · error · IOException

Unfinished quote at

Error message

Unfinished quote %s at %s

What it means

ShellQuotedParamsFilePreProcessor tokenizes a shell-quoted params file character by character, tracking quotes starting at a position (quoteStart). If end-of-input is reached while still inside a quote, it throws IOException 'Unfinished quote' with the quote character and the 1-based position where the quote opened. Parsing aborts before the tokens ever reach option parsing.

Solutions

1. Open the params file at the reported position and add the matching closing quote
2. Prefer --param_file=file_format=multiline (one arg per line, no shell quoting) when values contain quotes or backslashes
3. Validate args files in CI: a quick check that single/double quote counts balance per POSIX rules

Example fix

# before (args.txt)
--per_file_copt="//third_party/.* @-Werror
# after
--per_file_copt="//third_party/.*@-Werror"
# or use multiline format: bazel build --param_file=file_format=multiline @args.txt

# POSIX-ish balance check for single and double quotes per line (outside comments)
while IFS= read -r line; do
  case "$line" in \#*) continue;; esac
  s=$(printf '%s' "$line" | tr -cd "'" | wc -c); d=$(printf '%s' "$line" | tr -cd '"' | wc -c)
  [ $((s % 2)) -eq 0 ] && [ $((d % 2)) -eq 0 ] || { echo "Unbalanced quotes: $line" >&2; exit 2; }
done < args.txt

When it happens

Trigger: A params file (default shell quoting) containing an unmatched single or double quote, e.g. a value like -Xss'-... or "C:\dir without a closing quote; also multi-line strings whose closing quote was lost.

Common situations: Hand-editing args files and dropping a closing quote; Windows paths with embedded quotes; escaping rules differing between the generating shell and Bazel's POSIX tokenizer; trailing quote removed by sed/cleanup scripts.

Related errors

• A params file must be the only argument
• Error reading params file
• Expected value after
• Annotated method name must start with 'get' followed by an…
• Can't set an option to accumulate multiple values and let…

AI-assisted analysis of bazelbuild/bazel@e6e199d060 (2026-08-14). Data as JSON: /api/errors/8bb9c02c2078ce4d. Report an issue: GitHub.

Appendix: source

Thrown at src/main/java/com/google/devtools/common/options/ShellQuotedParamsFilePreProcessor.java:134

            quoted = true;
            quoteStart = position;
          } else if (current == '\r') {
            char next = read();
            if (next == '\n') {
              return arg.toString();
            } else {
              unread(next);
              return arg.toString();
            }
          } else if (Character.isWhitespace(current)) {
            return arg.toString();
          } else {
            arg.append(current);
          }
        }
      }
      if (quoted) {
        throw new IOException(
            String.format(UNFINISHED_QUOTE_MESSAGE_FORMAT, "'", quoteStart));
      }
      return arg.toString();
    }
  }
}

View on GitHub (pinned to e6e199d060)