alibaba/arthas · error · IllegalArgumentException

Argument(s) is/are expected, type 'help tt' to read usage

Error message

Argument(s) is/are expected, type 'help tt' to read usage

What it means

Thrown by checkArguments() in the `tt` command when none of the meaningful options are supplied: no index, not record mode (-t), not delete-all, no watch expression, not list (-l), and no search expression. The command needs at least one action argument to know what to do.

Source

Thrown at core/src/main/java/com/taobao/arthas/core/command/monitor200/TimeTunnelCommand.java:271

        // 检查d/p参数是否有i参数配套
        if ((isDelete || isPlay) && null == index) {
            throw new IllegalArgumentException("Time fragment index is expected, please type -i to specify");
        }

        // 在t参数下class-pattern,method-pattern
        if (isTimeTunnel) {
            if (StringUtils.isEmpty(classPattern)) {
                throw new IllegalArgumentException("Class-pattern is expected, please type the wildcard expression to match");
            }
            if (StringUtils.isEmpty(methodPattern)) {
                throw new IllegalArgumentException("Method-pattern is expected, please type the wildcard expression to match");
            }
        }

        // 一个参数都没有是不行滴
        if (null == index && !isTimeTunnel && !isDeleteAll && StringUtils.isEmpty(watchExpress)
                && !isList && StringUtils.isEmpty(searchExpress)) {
            throw new IllegalArgumentException("Argument(s) is/are expected, type 'help tt' to read usage");
        }
    }

    /*
     * 记录时间片段
     */
    int putTimeTunnel(TimeFragment tt) {
        int indexOfSeq = sequence.getAndIncrement();
        timeFragmentMap.put(indexOfSeq, tt);
        return indexOfSeq;
    }

    @Override
    public void process(final CommandProcess process) {
        // 检查参数
        checkArguments();

        // ctrl-C support

View on GitHub (pinned to 21cf2e9ba5)

Solutions

1. Add at least one action option, e.g. `tt -l` to list, `tt -t ...` to record, or `tt -i <index>` to show a fragment.
2. Run `tt --help` (or `help tt`) to see supported actions.

Example fix

// before
tt
// after
tt -l

if (index == null && !isTimeTunnel && !isDeleteAll
        && StringUtils.isEmpty(watchExpress) && !isList
        && StringUtils.isEmpty(searchExpress)) {
    fail("tt needs at least one action argument");
}

null

null

When it happens

Trigger: Running a bare `tt` with no options at all.

Common situations: Typing `tt` expecting a menu or default action; piping an empty argument set; alias misconfiguration that drops all flags.

Related errors

• Time fragment index is expected, please type -i to specify
• Class-pattern is expected, please type the wildcard expressi
• Method-pattern is expected, please type the wildcard express
• Invalid line number: {}
• Line number must be greater than 0: {}

AI-assisted analysis of alibaba/arthas@21cf2e9ba5 (2026-08-14). Data as JSON: /api/errors/7f480ae52dc85b19. Report an issue: GitHub.