diff --git a/src/ledger/file.go b/src/ledger/file.go
index 57abd1a..5ee9027 100644
--- a/src/ledger/file.go
+++ b/src/ledger/file.go
@@ -3,10 +3,13 @@ package ledger
 import (
 	"bufio"
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"io/fs"
+	"io/ioutil"
 	"os"
+	"path"
 	"path/filepath"
 	"sort"
 	"unicode"
@@ -33,7 +36,27 @@ func (files Files) TempGetLastNLines(n int) ([]string, error) {
 }
 
 func (files Files) TempSetLastNLines(n int, lines []string) error {
-	panic("e")
+	p := files.paths()[0]
+	w, err := ioutil.TempFile(os.TempDir(), path.Base(p))
+	if err != nil {
+		return err
+	}
+	defer w.Close()
+
+	r, err := os.Open(p)
+	if err != nil {
+		return err
+	}
+	defer r.Close()
+
+	if _, err := peekLastNLines(w, r, n); err != nil {
+		return err
+	}
+	for i := range lines {
+		fmt.Fprintln(w, lines[i])
+	}
+
+	return errors.New(w.Name())
 }
 
 func peekLastNLines(w io.Writer, r *bufio.Reader, n int) ([]string, error) {