find: add -files0-from option

* bootstrap.conf (gnulib_modules): Add argv-iter and same-inode.
* find/defs.h (struct options): Add files0_from and ok_prompt_stdin
members.
* find/ftsfind.c (argv-iter.h, same-inode.h, xalloc.h): Add #include
for gnulib headers.
(process_all_startpoints): Change loop over starting point arguments
to a loop using the argv_iter gnulib module.
* find/parser.c (parse_table): Add option.
(parse_files0_from): Declare and define function.
(insert_exec_ok): Set options flag ok_prompt_stdin to true for
the -ok and -okdir action.
* find/util.c (usage): Add new option.
(set_option_defaults): Initialize new struct members.
* doc/find.texi (node Starting points): Add new section describing
the regular processing of starting points, and that with the new
option.  Also mention in the description of -ok and -okdir that they
conflict with the new option.
* find/find.1: Document the new option here as well.
* tests/find/files0-from.sh: Add test.
* tests/local.mk (all_tests): Reference it.
* NEWS (New features in find): Mention the new option.

1 files changed, 170 insertions, 0 deletions

diff --git a/tests/find/files0-from.sh b/tests/find/files0-from.sh
new file mode 100755
index 00000000..b930a999
--- /dev/null
+++ b/tests/find/files0-from.sh
@@ -0,0 +1,170 @@
+#!/bin/sh
+# Exercise -files0-from option.
+
+# Copyright (C) 2021 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"; fu_path_prepend_
+print_ver_ find
+
+# Option -files0-from requires a file name argument.
+returns_ 1 find -files0-from > out 2> err \
+  && grep 'missing argument.*files0' err \
+  || { grep . out err; fail=1; }
+
+# Option -files0-from must not be combined with passing starting points on
+# the command line.
+returns_ 1 find OFFENDING -files0-from FILE > out 2> err \
+  && grep 'extra operand .*OFFENDING' err \
+  && grep 'file operands cannot be combined with -files0-from' err \
+  || { grep . out err; fail=1; }
+
+# Process "." as default when starting points neither passed via -files0-from
+# nor on the command line.
+printf "%s\n" '.' > exp || framework_failure_
+find -maxdepth 0 > out 2> err || fail=1
+compare exp out || fail=1
+compare /dev/null err || fail=1
+
+# Option -files0-from with argument "-" (=stdin) must not be combined with
+# the -ok action: getting the user confirmation would mess with stdin.
+returns_ 1 find -files0-from - -ok echo '{}' ';' < /dev/null > out 2> err \
+  && grep 'files0.* standard input .*cannot be combined with .*ok' err \
+  || { grep . out err; fail=1; }
+
+# Option -files0-from with argument "-" (=stdin) must not be combined with
+# the -okdir action: getting the user confirmation would mess with stdin.
+returns_ 1 find -files0-from - -okdir echo '{}' ';' < /dev/null > out 2> err \
+  && grep 'files0.* standard input .*cannot be combined with .*ok' err \
+  || { grep . out err; fail=1; }
+
+# File argument of -files0-from option must not refer to the same file as stdin.
+printf '.' > in || framework_failure_
+returns_ 1 find -files0-from in -ok echo '{}' ';' < in > out 2> err \
+    && grep 'files0.* standard input .*same file .*with -ok, -okdir' err \
+  || { grep . out err; fail=1; }
+
+# Likewise via a symlink.
+if ln -s in inlink; then
+  returns_ 1 find -files0-from inlink -ok echo '{}' ';' < in > out 2> err \
+    && grep 'files0.* standard input .*same file .*with -ok, -okdir' err \
+    || { grep . out err; fail=1; }
+  # ... and vice versa.
+  returns_ 1 find -files0-from in -ok echo '{}' ';' < inlink > out 2> err \
+    && grep 'files0.* standard input .*same file .*with -ok, -okdir' err \
+    || { grep . out err; fail=1; }
+fi
+
+# Likewise when the system provides the name '/dev/stdin'.
+if ls /dev/stdin >/dev/null 2>&1; then
+  returns_ 1 find -files0-from /dev/stdin -ok echo '{}' ';' < in > out 2> err \
+    && grep 'files0.* standard input .*same file .*with -ok, -okdir' err \
+    || { grep . out err; fail=1; }
+fi
+
+# Exercise a non-existing file.
+returns_ 1 find -files0-from ENOENT > out 2> err \
+  && grep 'cannot open .ENOENT. for reading: No such' err \
+  || { grep . out err; fail=1; }
+
+# Exercise a file which cannot be opened.
+# The shadow(5) file seems to be a good choice for reasonable coverage.
+f='/etc/shadow'
+if test -e $f && test '!' -r $f; then
+  returns_ 1 find -files0-from $f > out 2> err \
+  && grep 'cannot open .* for reading: Permission denied' err \
+  || { grep . out err; fail=1; }
+fi
+
+# Exercise a directory argument.
+returns_ 1 find -files0-from / > out 2> err \
+  && grep 'read error' err \
+  || { grep . out err; fail=1; }
+
+# Exercise an empty input file.
+returns_ 1 find -files0-from /dev/null > out 2> err || fail=1
+compare /dev/null out || fail=1
+grep 'file with starting points is empty:' err || fail=1
+
+# Likewise via stdin.
+returns_ 1 find -files0-from - < /dev/null > out 2> err || fail=1
+compare /dev/null out || fail=1
+grep 'file with starting points is empty:.*standard input' err || fail=1
+
+# Likewise via a pipe on stdin.
+cat /dev/null | returns_ 1 find -files0-from - > out 2> err || fail=1
+compare /dev/null out || fail=1
+grep 'file with starting points is empty:.*standard input' err || fail=1
+
+# Now a regular case: 2 files: expect the same output.
+touch a b || framework_failure_
+printf '%s\0' a b > in || framework_failure_
+tr '\0' '\n' < in > exp || framework_failure_
+find -files0-from in -print > out 2> err || fail=1
+compare exp out || fail=1
+compare /dev/null err || fail=1
+
+# Demonstrate that -files0-from accepts file names which would otherwise be
+# rejected because they are recognized as test or action.
+touch ./-print ./-mtime ./-size || framework_failure_
+printf '%s\0' _print _mtime _size | tr '_' '-' > in || framework_failure_
+tr '\0' '\n' < in > exp || framework_failure_
+find -files0-from in -printf '%p\n' > out 2> err || fail=1
+compare exp out || fail=1
+compare /dev/null err || fail=1
+
+# Zero-length file name on position 2, once per stdin ...
+printf '%s\n' a b > exp || framework_failure_
+printf '%s\0' a '' b \
+  | tee file \
+  | returns_ 1 find -files0-from - -print > out 2> err || fail=1
+compare exp out || fail=1
+grep '(standard input).:2: invalid zero-length file name' err || fail=1
+# ... and once per file.
+returns_ 1 find -files0-from file -print > out 2> err || fail=1
+compare exp out || fail=1
+grep 'file.:2: invalid zero-length file name' err || fail=1
+
+# Non-existing file name.
+printf '%s\0' a ENOENT b \
+  | returns_ 1 find -files0-from - -print > out 2> err || fail=1
+compare exp out || fail=1
+grep 'ENOENT' err || fail=1
+
+# Demonstrate (the usual!) recursion ...
+mkdir d1 d1/d2 d1/d2/d3 && touch d1/d2/d3/file || framework_failure_
+printf '%s\n' d1 d1/d2 d1/d2/d3 d1/d2/d3/file > exp || framework_failure_
+printf 'd1' \
+  | find -files0-from - > out 2> err || fail=1
+compare exp out || fail=1
+compare /dev/null err || fail=1
+# ... and how to avoid recursion with -maxdepth 0.
+find d1 -print0 \
+  | find -files0-from - -maxdepth 0 > out 2> err || fail=1
+compare exp out || fail=1
+compare /dev/null err || fail=1
+
+# Large input with files.
+# Create file 'exp' with many times its own name as content, NUL-separated;
+# and let find(1) check that it worked (4x in bytes).
+yes exp | head -n 100000 | tr '\n' '\0' > exp \
+  && find exp -size 400000c | grep . || framework_failure_
+# Run the test.
+find -files0-from exp > out 2> err || fail=1
+# ... and verify.
+test $( wc -l < out ) = 100000 || fail=1
+find out -size 400000c | grep . || fail=1
+
+Exit $fail