diff --git a/go/tests/prog/ztail_prog/main.go b/go/tests/prog/ztail_prog/main.go
index 74415fc0..a9866e0b 100644
--- a/go/tests/prog/ztail_prog/main.go
+++ b/go/tests/prog/ztail_prog/main.go
@@ -6,10 +6,20 @@ import (
 	"os"
 )
 
-func check(err error) {
+const (
+	success = iota
+	failure
+)
+
+var status = success
+
+func notNil(err error) bool {
 	if err != nil {
-		panic(err)
+		status = failure
+		fmt.Fprintln(os.Stderr, err)
+		return true
 	}
+	return false
 }
 func main() {
 	var bytes int64
@@ -18,23 +28,30 @@ func main() {
 	filenames := flag.Args()
 	for i, filename := range filenames {
 		file, err := os.Open(filename)
-		check(err)
+		if notNil(err) {
+			continue
+		}
 		defer file.Close()
 		fileInfo, err := file.Stat()
-		check(err)
+		if notNil(err) {
+			continue
+		}
 		offset := fileInfo.Size() - bytes
 		if offset < 0 {
 			offset = 0
 		}
 		b := make([]byte, fileInfo.Size()-offset)
 		_, err = file.ReadAt(b, offset)
-		check(err)
+		if notNil(err) {
+			continue
+		}
 		if len(filenames) > 1 {
+			if i > 0 {
+				fmt.Println()
+			}
 			fmt.Println("==>", filename, "<==")
 		}
 		os.Stdout.Write(b)
-		if i < len(filenames)-1 {
-			fmt.Println()
-		}
 	}
+	os.Exit(status)
 }
diff --git a/subjects/ztail/README.md b/subjects/ztail/README.md
index 78b1630c..b5adef70 100644
--- a/subjects/ztail/README.md
+++ b/subjects/ztail/README.md
@@ -4,8 +4,48 @@
 
 Write a program that behaves like a simplified `tail` command but which takes at least one file as argument.
 
-- The only option to be handled is `-c`. This option will be used in all the tests as the first argument, with positive values.
+The only option to be handled is `-c` and will be used in all the tests as the first argument, with positive values.
 
-- For this program the `os` package can be used.
+For this program the `os` package can be used.
 
-- Handle the errors by returning a non-zero exit status.
+Handle the errors by returning a non-zero exit status but process all the files.
+
+If several files are given, print a new line and the file name between each one of them (see below).
+
+### Usage
+
+If `file1.txt` & `file2.txt` contains :
+
+```
+abcdefghijklmnopqrstuvwxyz
+```
+
+Normal cases :
+
+```
+$ ./ztail -c 4 file1.txt
+xyz
+$ ./ztail -c 4 file1.txt file2.txt
+==> file1.txt <==
+xyz
+
+==> file2.txt <==
+xyz
+$
+```
+
+Error cases :
+
+```
+$ ./ztail -c 4 file1.txt nonexisting1.txt file2.txt nonexisting2.txt
+==> file1.txt <==
+xyz
+open nonexisting1.txt: no such file or directory
+
+==> file2.txt <==
+xyz
+open nonexisting2.txt: no such file or directory
+$ echo $?
+1
+$
+```