I need some help with regular expression.
I need to search for "Android 2.2.x" where x can be 1-9 in a string so I created this RegEx Androind 2.2.\d{1} This works fine.
Now I want to find Android 2.2 in the in the string
If I search using Regex "Androind 2.2" it matches both "Android 2.2" and "Android 2.2.x" But I want regex to match only "Android 2.2"
Can anyone please help me with this.
Thanks,
Use negative lookahead. "Android 2.2(?!\.\d)" matches "Android 2.2" but not "Android 2.2.1", "Android 2.2.2", "Android 2.2.10", etc. It will also match "Android 2.2." if the next character is not a digit or the end of the string is reached.
See Grouping Constructs for more information.
(?!\.?\d) to prevent that.
"Android 2.2(?!\.\d)" also matches "Android 2.20", so if you need to future-proof yourself for 18 versions from now you might try "Android 2.2(?!\.?\d)" (make the period in the assertion optional).If this string Android 2.2 is followed by end of string, you can include $ after the pattern which matches the end of string.
Otherwise, you can do something like Android 2.2[^0-9.] to make sure that this string is not followed by dot or digits.
One argument against the second case is that you could have a string like "You are using Andoid 2.2." Where the last . is there to just end a sentence... Would you like to match that string as well?
Just to toss out another approach, if you need to provide different behavior for different versions you could do this:
string pattern = @"Android (?<major>\d+)\.(?<minor>\d+)(\.(?<revision>\d+))?";
Match match = Regex.Match(text, pattern);
if (match.Success)
{
int major = int.Parse(match.Groups["major"].Value);
int minor = int.Parse(match.Groups["minor"].Value);
int revision;
if (!int.TryParse(match.Groups["revision"].Value, out revision))
revision = 0;
if (major == 2 && minor == 2)
{
if (revision == 0)
{
// Process version 2.2
}
else
{
// Process version 2.2.x, where x > 0
}
}
}
That will match a major version followed by a minor version optionally followed by a revision, and give you access to each of those three numbers. Note that if no revision is specified it's treated the same as if it were 0 (i.e. "Android 2.2" == "Android 2.2.0").
You can also use the Version class to do some of the work, like this:
string pattern = @"Android (?<version>\d+\.\d+(\.\d+)?)";
Match match = Regex.Match(text, pattern);
if (match.Success)
{
Version version = Version.Parse(match.Groups["version"].Value);
if (version.Major == 2 && version.Minor == 2)
{
if (version.Build < 1)
{
// Process version 2.2
}
else
{
// Process version 2.2.x, where x > 0
}
}
}
There the third number component is called "Build", not "Revision". Note that the Build property returns 0 if the value is 0 and -1 if the value is not specified.
\d{1}if you just need one digit,\dwill do.