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  | 
diff --git a/nixfig.go b/nixfig.go
index b91d34929c055cd58708980b26f806baee668465..d89e98b2bd19bb7fc9ac5033d11abe738f6a97e4 100644
--- a/nixfig.go
+++ b/nixfig.go
@@ -7,12 +7,14 @@ 	"errors"
 	"fmt"
 	"os"
 	"os/exec"
+	"strings"
 )
 
 var (
-	// Nix is the command to call for nix
-	Nix            string
+	Nix            string   // Nix is the command to call for nix
+	Fmt            []string // Fmt is the command (and args) to call to format the nix output
 	ErrNixNotFound = errors.New("nix was not found or set. You can set it either with `nixfig.Nix` or the `NIXFIG_NIX` environment variable")
+	ErrFmtNotFound = errors.New("nix formatter was not found or set. You can set it either with `nixfig.Fmt` or the `NIXFIG_FMT` environment variable")
 )
 
 func init() {
@@ -20,6 +22,17 @@ 	nixPath, _ := exec.LookPath("nix")
 	Nix = nixPath
 	if envPath, ok := os.LookupEnv("NIXFIG_NIX"); ok {
 		Nix = envPath
+	}
+
+	for _, formatter := range []string{"alejandra", "nixfmt-rfc-style", "nixfmt"} {
+		fmtPath, _ := exec.LookPath(formatter)
+		if fmtPath != "" {
+			Fmt = []string{fmtPath, "--quiet"}
+			break
+		}
+	}
+	if envPath, ok := os.LookupEnv("NIXFIG_FMT"); ok {
+		Fmt = strings.Split(envPath, " ")
 	}
 }
 
@@ -70,3 +83,29 @@ 	}
 
 	return stdout.Bytes(), nil
 }
+
+// MarshalFormat marshals a struct into a nix expression and formats it with Fmt
+func MarshalFormat(v any) ([]byte, error) {
+	if Fmt == nil {
+		return nil, ErrFmtNotFound
+	}
+
+	data, err := Marshal(v)
+	if err != nil {
+		return nil, err
+	}
+
+	var stdout, stderr bytes.Buffer
+	cmd := exec.Command(Fmt[0], Fmt[1:]...)
+	cmd.Stdin = bytes.NewBuffer(data)
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+	if err := cmd.Run(); err != nil {
+		return nil, fmt.Errorf("could not run %v: %w", Fmt, err)
+	}
+	if stderr.Len() > 0 {
+		return nil, errors.New(stderr.String())
+	}
+
+	return stdout.Bytes(), nil
+}
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