RegEx targeted replace with Named Captures - regex

Question

Given
$line = '{initError-[cf][3]}_Invalid nodes(s): [3]'
I can use
$line -match '^\{(?<type>[a-z]+)(-\[(?<target>(C|F|CF))\])?(\[(?<tab>\d+)\])?\}_(?<string>.*)'
And $matches['tab'] will correctly have a value of 3. However, if I then want to increment that value, without also affecting the [3] in the string section things get more complicated. I can use $tabIndex = $line.indexOf("[$tab]") to get the index of the first occurrence, and I can also use $newLine = ([regex]"\[$tab\]").Replace($line, '[4]', 1) to only replace the first occurrence. But I wonder, is there a way to get at the this more directly? It's not strictly necessary, as I will only ever want to replace things within the initial {}_, which has a very consistent form, so replacing first instance works, just wondering if I am missing out on a more elegant solution, which also might be needed in a different situation.

Answer 1

I would change the regex a bit, because mixing Named captures with Numbered captures is not recommended, so it becomes this:
'^\{(?<type>[a-z]+)(?:-\[(?<target>[CF]{1,2})\])?(?:\[(?<tab>\d+)\])?\}_(?<string>.*)'
You could then use it like below to replace the tab value:
$line = '{initError-[cf][3]}_Invalid nodes(s): [3]'
$newTabValue = 12345
$line -replace '^\{(?<type>[a-z]+)(?:-\[(?<target>[CF]{1,2})\])?(?:\[(?<tab>\d+)\])?\}_(?<string>.*)', "{`${type}-[`${target}][$newTabValue]}_`${string}"
The result of this will be:
{initError-[cf][12345]}_Invalid nodes(s): [3]
Regex details:
^ Assert position at the beginning of the string
\{ Match the character “{” literally
(?<type> Match the regular expression below and capture its match into backreference with name “type”
[a-z] Match a single character in the range between “a” and “z”
+ Between one and unlimited times, as many times as possible, giving back as needed (greedy)
)
(?: Match the regular expression below
- Match the character “-” literally
\[ Match the character “[” literally
(?<target> Match the regular expression below and capture its match into backreference with name “target”
[CF] Match a single character present in the list “CF”
{1,2} Between one and 2 times, as many times as possible, giving back as needed (greedy)
)
\] Match the character “]” literally
)? Between zero and one times, as many times as possible, giving back as needed (greedy)
(?: Match the regular expression below
\[ Match the character “[” literally
(?<tab> Match the regular expression below and capture its match into backreference with name “tab”
\d Match a single digit 0..9
+ Between one and unlimited times, as many times as possible, giving back as needed (greedy)
)
\] Match the character “]” literally
)? Between zero and one times, as many times as possible, giving back as needed (greedy)
\} Match the character “}” literally
_ Match the character “_” literally
(?<string> Match the regular expression below and capture its match into backreference with name “string”
. Match any single character that is not a line break character
* Between zero and unlimited times, as many times as possible, giving back as needed (greedy)
)

Answer 2

An alternative way of increasing the first number in the brackets is using the -Split operator to access the number you want to change:
$line = '{initError-[cf][3]}_Invalid nodes(s): [3]'
$NewLine = $line -split "(\d+)"
$NewLine[1] = [int]$newLine[1] + 1
-join $NewLine
Output:
{initError-[cf][4]}_Invalid nodes(s): [3]