如何编写C#正则表达式模式以匹配基本的printf格式字符串,如“%5.2f”?

这应该做到:

string input = "Bloke %s drank %5.2f litres of water and ate %d bananas";
string pattern = @"%(\d+(\.\d+)?)?(d|f|s)";

foreach (Match m in Regex.Matches(input, pattern))
{
    Console.WriteLine(m.Value);
}

我没用 [dfs] 在我的模式中,因为我计划将其更新为使用命名组。这是基于 your earlier question 关于找出C样式格式字符串的替换策略。

有个主意:

string input = "Bloke %s drank %5.2f litres of water and ate %d bananas";
string pattern = @"%(?<Number>\d+(\.\d+)?)?(?<Type>d|f|s)";

int count = 0;
string result = Regex.Replace(input, pattern, m =>
{
    var number = m.Groups["Number"].Value;
    var type = m.Groups["Type"].Value;
    // now you can have custom logic to check the type appropriately
    // check the types, format with the count for the current parameter
    return String.Concat("{", count++, "}");
});

C#/.NET 2.0方法:

private int formatCount { get; set; }

void Main()
{
    string input = "Bloke %s drank %5.2f litres of water and ate %d bananas";
    Console.WriteLine(FormatCStyleStrings(input));  
}

private string FormatCStyleStrings(string input)
{
    formatCount = 0; // reset count
    string pattern = @"%(?<Number>\d+(\.\d+)?)?(?<Type>d|f|s)";
    string result = Regex.Replace(input, pattern, FormatReplacement);
    return result;
}

private string FormatReplacement(Match m)
{
    string number = m.Groups["Number"].Value;
    string type = m.Groups["Type"].Value;
    // custom logic here, format as needed
    return String.Concat("{", formatCount++, "}");
}

%(?:\d+)?(?:\.\d+)?[dfs]

是你问题的答案,但我怀疑你可能问错了,因为 printf 承认而不是那样。

下面是一个表达式,它匹配printf/scanf函数格式字符串的所有字段。

(?<!%)(?:%%)*%([\-\+0\ \#])?(\d+|\*)?(\.\*|\.\d+)?([hLIw]|l{1,2}|I32|I64)?([cCdiouxXeEfgGaAnpsSZ])

它基于 Format Fields Specification %[flags][width][.precision][{h|l|ll|L|I|I32|I64|w}]type 匹配组将包含: #1 - flags, #2 - width, #3 - precision, #4 - size prefix, #5 - type.

取自 here .