---
name: "function::ngroups"
section: "3stap"
platform: "linux"
package: "systemtap-doc"
version: "5.1-5"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/function::ngroups"
---

# function::ngroups(3stap)

Number of subexpressions in the last match.

## NAME

function::ngroups - Number of subexpressions in the last match.

## SYNOPSIS

```
    ngroups:long()
```

## ARGUMENTS

None

## DESCRIPTION

returns the number of subexpressions from the last successful use of the =~ regex matching operator.

Note that this number includes subexpressions which are present in the regex but did not match any string; for example, given the regex “a\|(b)”, the subexpressions will count the group for (b) regardless of whether it matched a string or not. Throws an error if the last use of =~ was a failed match.

## SEE ALSO0

[*tapset::regex*(3stap)](/tapset::regex/3stap.md)