tests: head: test 'head -n 0' and 'head -c 0' open files for reading

* tests/head/head-n0.sh: New file.
* tests/local.mk: Add the new test case.

diff --git a/tests/head/head-n0.sh b/tests/head/head-n0.sh
new file mode 100755 (executable)
index 0000000..8da4597
--- /dev/null
+++ b/tests/head/head-n0.sh
@@ -0,0 +1,81 @@
+#!/bin/sh
+# Make sure that 'head -n 0' and 'head -c 0' opens files for reading.
+
+# Copyright (C) 2026 Free Software Foundation, Inc.
+
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+. "${srcdir=.}/tests/init.sh"; path_prepend_ ./src
+print_ver_ head
+getlimits_
+
+mkdir dir || framework_failure_
+echo a > file || framework_failure_
+
+# Test 'head -n 0' with an existing file or directory.
+for args in dir file; do
+  for opt in -n -c; do
+    head $opt 0 $args >out 2>err || fail=1
+    compare /dev/null out || fail=1
+    compare /dev/null err || fail=1
+  done
+done
+
+# Test 'head -n 0' with multiple existing arguments and headers disabled.
+for args in 'dir file' 'file dir'; do
+  for opt in -n -c; do
+    head -q $opt 0 $args >out 2>err || fail=1
+    compare /dev/null out || fail=1
+    compare /dev/null err || fail=1
+  done
+done
+
+# Test 'head -n 0' with multiple existing arguments and headers enabled.
+for args in 'dir file' 'file dir'; do
+  file1=$(echo "$args" | cut -d ' ' -f1)
+  file2=$(echo "$args" | cut -d ' ' -f2)
+  cat <<EOF > exp || framework_failure_
+==> $file1 <==
+
+==> $file2 <==
+EOF
+  for opt in -n -c; do
+    head $opt 0 $args >out 2>err || fail=1
+    compare exp out || fail=1
+    compare /dev/null err || fail=1
+  done
+done
+
+# Test 'head -n 0' with a missing file.
+cat <<EOF >exp || framework_failure_
+head: cannot open 'missing1' for reading: $ENOENT
+EOF
+for opt in -n -c; do
+  returns_ 1 head $opt 0 missing1 >out 2>err || fail=1
+  compare /dev/null out || fail=1
+  compare exp err || fail=1
+done
+
+# Test 'head -n 0' with multiple missing files.
+cat <<EOF >exp || framework_failure_
+head: cannot open 'missing1' for reading: $ENOENT
+head: cannot open 'missing2' for reading: $ENOENT
+EOF
+for opt in -n -c; do
+  returns_ 1 head $opt 0 missing1 missing2 >out 2>err || fail=1
+  compare /dev/null out || fail=1
+  compare exp err || fail=1
+done
+
+Exit $fail

diff --git a/tests/local.mk b/tests/local.mk
index d72361e40c4986a339e8818199924cd6893c38db..727cf8b58b84d1062cb056d186399e53f9ca949d 100644 (file)
--- a/tests/local.mk
+++ b/tests/local.mk
@@ -365,6 +365,7 @@ all_tests =                                 \
   tests/groups/groups-process-all.sh           \
   tests/groups/groups-version.sh               \
   tests/head/head-c.sh                         \
+  tests/head/head-n0.sh                                \
   tests/head/head-pos.sh                       \
   tests/head/head-write-error.sh               \
   tests/misc/kill.sh                           \