RegEx
A RegEx (short for Regular Expression), is a string of text that allows you to match on specific patterns of text. For example, if you were given the text "tag_name": "v1.2.3", a small RegEx could be used to extract the version number in semantic form (‘1.2.3’), [0-9]+. (this would match on all cases of 1 or more of 0-9 in the target string)
With Argus, RegEx can be used in a few places
service.name.regex_content- RegEx used on the content of the page @urlthat needs to match before Argus considers it a valid version.service.name.regex_version- RegEx used on the version found that needs to match before Argus considers it a valid version.service.url_commands[*].regex- RegEx used in aurl_commandto extract the version from the page.service.deployed_version.regex- RegEx to get thedeployed_versionfrom the page @url
| Character | Description | Example | Matches |
|---|---|---|---|
| ^ | Matches beginning of line | ^any | allow,any |
| $ | Matches end of line | y$ | friendly,yay |
| . | Match any character | a.c | abc,a_c |
| | | OR operator | a1 | b1 |
| (…) | Capture anything matched | v(1) | captures 1 |
| […] | Matches anything contained in the brackets | [abc] | a,b,c |
| [^…] | Matches anything not contained in the brackets | [^abc] | d,e,f |
| [a-z] | Matches any character between ‘a’ and ‘z’ (inclusive) | [a-z] | a,r,g |
| [0-9] | Matches any number between ‘0’ and ‘9’ (inclusive) | [0-2] | 0,1,2 |
| {x} | match ‘x’ amount of times | (ab){2} | abab |
| {x,} | match ‘x’ or more amount of times | (ab){2,} | abab, ababab |
| {x,y} | match between ‘x’ and ‘y’ times | (ab){1,2} | ab, abab |
| * | Match 0+ of the item before it | ab*c | ac,abc,abbc |
| + | Match 1+ of the item before it | ab+c | abc,abbc,abbc |
| ? | Match 0/1 of the item before it | ab?c | ac,abc |
| \ | Escape the character after it | 1\.2,dev\* | 1.2, dev* (won’t match 132 or de) |
Sometimes the sites you query will have multiple matches for your regex, e.g.
beta:
version: "2.0.0-dev"
stable:
version: "1.0.5"
If you wanted stable.version, you could use the version: "([^"]+)" RegEx. Though on its own, this would match both the ‘2.0.0-dev’ and the ‘1.0.5’. Argus would take the first match by default. You can get around this by giving your url_commands an index. So using this RegEx, but with an index of ‘1’ would give you the second match (as indexes start from 0).
An alternative would be to make the version number RegEx a bit stricter. Here, we have -dev in the beta release, so if it’s like that on all betas, we could make the RegEx exclude those cases like so, version: "([0-9.]+)". Now the RegEx is only allowing the version to be a sequence of numbers and full stops. This would give us ‘1.0.5’.
Helpful sites
You can test your regex on the sites below and see what it’s matching as well as why