When constructing dynamic shell commands for SSH execution within a Java application, silent failures may occur if numeric arguments are formatted unexpectedly. A specific scenario involves a query command that returns data when executed manually but yields empty results when triggered by the application. Inspection of system logs reveals no exceptions, yet the data retrieval fails consistently.

Debugging the Formatting Logic

Initial analysis of the response parsing logic shows no discrepancies. The focus shifts to the command construction phase. Up on reviewing the logged output of the generated command, a stray comma appears with in the numeric parameter. For instance, an expected value of 5000 apears as 5,000.

The root cause lies in the usage of java.text.MessageFormat. When a numeric type is passed as an argument, MessageFormat applies the default NumberFormat for the current locale. This behavior automatically inserts grouping separators (commas) for values exceeding three digits.

public int fetchRecordId() {
    // Returns 5000
    return 5000;
}

public String buildSshCommand() {
    // Expected: retrieve record 5000
    // Actual: retrieve record 5,000
    String cmd = MessageFormat.format("retrieve record {0}", fetchRecordId());
    return cmd;
}

The inserted comma invalidates the shell command, preventing the remote system from recognizing the argument.

Mitigation Strategies

To prevent implicit grouping separators, the numeric argument can be explicitly converted to a string before formatting.

public String buildSshCommand() {
    // Convert integer to string to bypass number formatting
    String cmd = MessageFormat.format("retrieve record {0}", String.valueOf(fetchRecordId()));
    return cmd;
}

Alternatively, the format pattern itself can be modified to specify a style that disables grouping. Using the # symbol ensures the number is rendered without separators.

public String buildSshCommand() {
    // Define format style to exclude grouping separators
    String cmd = MessageFormat.format("retrieve record {0, number, #}", fetchRecordId());
    return cmd;
}