Regex named group problem C#
I'm trying to write a regex with named captures in C# to parse cron jobs. The problem, however, is that both using single quote and bracket named capture groups the values return blank. For example, with the input
*/15 * * * * * http://www.google.com/
this code:
Regex cronRe = new Regex(@"(?<minutes>[\d\*\-,]+) (?<hours>[\d\*\-,]+) (?<days>[\d\*\-,]+) (?<months>[\d\*\-,]+) (?<dotw>[\开发者_运维百科d\*\-,]+) (?<years>[\d\*\-,]+) (?<command>[\d\*\-,]+)");
//loop through jobs and do them
for (int i = 0; i < lines.Length; i++)
{
Match line = logRe.Match(lines[i]);
bool runJob = true;
for (int j = 0; j < line.Groups.Count; j++)
{
Console.Write(j.ToString() + ": " + line.Groups[j].Value + "\n");
}
Console.Write("named group minutes: " + line.Groups["minutes"].Value);
}
return with this:
0: */15 * * * * * http://www.google.com
1: */15 * 2: * 3: * 4: * 5: * 6: http://www.google.com named group minutes:
any suggestions?
I believe you want something like this (line-wrapped for readability):
^
(?<minutes>[\d*,/-]+)\s
(?<hours>[\d*,/-]+)\s
(?<days>[\d*,/-]+)\s
(?<months>[\d*,/-]+)\s
(?<dotw>[\d*,/-]+)\s
(?<years>[\d*,/-]+)\s
(?<command>.*)
$
Notes:
- The expression must be properly anchored (at least "^").
- The dash has special meaning in character classes (it creates ranges). If you want to match a literal dash, put it at the end of the character class.
- You don't need to escape the star within a character classes.
Apart from that: The expression ([\d*,/-]+)
is fairly unspecific. I'd do it with more input validation:
(\d+(?:-\d+)?(?:,\d+(?:-\d+)?)*(?:,\*)?|\*(?:/\d+)?)
Explanation
(
\d+ // matches numbers ("3")
(?:-\d+)? // with the above: matches ranges ("3-4")
(?: // optional
,\d+ // matches more numbers ("3,6")
(?:-\d+)? // matches more ranges ("3,6-9")
)* // allows repeat ("3,6-9,11")
(?:,\*)? // allows star at the end ("3,6-9,11,*")
| // alternatively...
\*(?:/\d+)? // allows star with optional filter ("*" or "*/15")
)
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