From df570102af7830457de7e6acaba300c4b3b5b7fc Mon Sep 17 00:00:00 2001
From: Rob Landley <rob@landley.net>
Date: Mon, 28 Apr 2025 17:39:27 -0500
Subject: [PATCH] Implement chmod -cv

---
 tests/chmod.test   | 34 ++++++++++++++++++++--------------
 toys/posix/chmod.c | 45 +++++++++++++++++++++++++++++++++++----------
 2 files changed, 55 insertions(+), 24 deletions(-)

diff --git a/tests/chmod.test b/tests/chmod.test
index 8c4f5e63..31233ab9 100755
--- a/tests/chmod.test
+++ b/tests/chmod.test
@@ -29,27 +29,27 @@ for U in $(seq 0 7); do for G in 0 3 6; do for O in 0 7; do for T in dir file; d
   rm -rf $T
   if [ "$T" == file ]; then
     touch file
-    C=-
+    D=-
   else
     mkdir dir
-    C=d
+    D=d
   fi
-  testing "$U$G$O $T" "chmod $U$G$O $T && ls -ld $T | cut -d' ' -f 1" \
-    "${C}$(num2perm $U$G$O)\n" "" ""
+  testcmd "$U$G$O $T" "$U$G$O $T && ls -ld $T | cut -d' ' -f 1" \
+    "${D}$(num2perm $U$G$O)\n" "" ""
 done; done; done; done
-unset U G O T C
+unset U G O T D
 
 rm -rf dir file && mkdir dir && touch file 640
-testing "750 dir 640 file" "chmod 750 dir 640 file &&
+testcmd "750 dir 640 file" "750 dir 640 file &&
   ls -ld 640 dir file | cut -d' ' -f 1 | cut -d. -f 1" \
   "-rwxr-x---\ndrwxr-x---\n-rwxr-x---\n" "" ""
 
 chtest()
 {
-  chmod -fR 700 dir file 2>/dev/null
+  chmod -fR 700 dir file
   rm -rf dir file && mkdir dir && touch file
-  testing "$1 dir file" \
-    "chmod $1 dir file && ls -ld dir file | cut -d' ' -f 1 | cut -d. -f 1" \
+  testcmd "$1 dir file" \
+    "$1 dir file && ls -ld dir file | cut -d' ' -f 1 | cut -d. -f 1" \
     "$2" "" ""
 }
 
@@ -103,9 +103,7 @@ chtest -x "drw-r--r--\n-rw-r--r--\n"
 chtest a-w,a+x "dr-xr-xr-x\n-r-xr-xr-x\n"
 
 # macOS doesn't allow +s in /tmp
-touch s-supported
-chmod +s s-supported 2>/dev/null || SKIP=99
-rm s-supported
+[ "$(uname)" == Darwin ] && SKIP=99
 chtest g+s "drwxr-sr-x\n-rw-r-Sr--\n"
 chtest u+s "drwsr-xr-x\n-rwSr--r--\n"
 chtest +s "drwsr-sr-x\n-rwSr-Sr--\n"
@@ -125,9 +123,17 @@ testing "+X" \
 mkdir foo
 ln -s bar foo/baz
 # If you explicitly ask us, we'll try (and fail) to chmod a symlink.
-testing "-R symlink arg" 'chmod -R 750 foo/baz 2>/dev/null; echo $?' "1\n" "" ""
+testcmd "-R symlink arg" '-R 750 foo/baz 2>/dev/null; echo $?' "1\n" "" ""
 # If you only imply that you might want us to do that, we'll skip it.
-testing "-R symlink recurse" 'chmod -R 750 foo; echo $?' "0\n" "" ""
+testcmd "-R symlink recurse" '-R 750 foo; echo $?' "0\n" "" ""
+touch one
+testcmd '-c' '-c u+x one && chmod -c u+x one && chmod -c u+x one' \
+  "mode of 'one' changed from 0644 (rw-r--r--) to 0744 (rwxr--r--)\n" "" ""
+rm one; touch one
+testcmd '-v' '-v u+x one && chmod -v u+x one && chmod -v u+x one' \
+  "mode of 'one' changed from 0644 (rw-r--r--) to 0744 (rwxr--r--)
+mode of 'one' retained as 0744 (rwxr--r--)
+mode of 'one' retained as 0744 (rwxr--r--)\n" "" ""
 
 # Removing test files for cleanup purpose
 rm -rf dir file
diff --git a/toys/posix/chmod.c b/toys/posix/chmod.c
index ef74c4fa..dc9630e3 100644
--- a/toys/posix/chmod.c
+++ b/toys/posix/chmod.c
@@ -3,8 +3,10 @@
  * Copyright 2012 Rob Landley <rob@landley.net>
  *
  * See http://opengroup.org/onlinepubs/9699919799/utilities/chmod.html
+ *
+ * Deviations from posix: -cfv
 
-USE_CHMOD(NEWTOY(chmod, "<2?vfR[-vf]", TOYFLAG_BIN))
+USE_CHMOD(NEWTOY(chmod, "<2?cvfR[-cvf]", TOYFLAG_BIN))
 
 config CHMOD
   bool "chmod"
@@ -12,9 +14,16 @@ config CHMOD
   help
     usage: chmod [-R] MODE FILE...
 
-    Change mode of listed file[s] (recursively with -R).
+    Change permission mode of listed file[s] to be readable, writeable, and/or
+    executable to the current user, the file's group, or other (everyone else).
+    You can also set/clear the suid, guid, and sticky bits.
+
+    -c	Print changes
+    -f	Don't print errors
+    -R	Recursive
+    -v	Verbose
 
-    MODE can be (comma-separated) stanzas: [ugoa][+-=][rwxstXugo]
+    MODE can be octal or (comma-separated) stanzas of [ugoa][+-=][rwxstXugo]
 
     Stanzas are applied in order: For each category (u = user,
     g = group, o = other, a = all three, if none specified default is a),
@@ -25,7 +34,7 @@ config CHMOD
     X = x for directories or if any category already has x set.
 
     Or MODE can be an octal value up to 7777	ug uuugggooo	top +
-    bit 1 = o+x, bit 1<<8 = u+w, 1<<11 = g+1	sstrwxrwxrwx	bottom
+    bit 1 = o+x, bit 1<<8 = u+r, 1<<10 = g+s	sstrwxrwxrwx	bottom
 
     Examples:
     chmod u+w file - allow owner of "file" to write to it.
@@ -41,7 +50,8 @@ GLOBALS(
 
 static int do_chmod(struct dirtree *try)
 {
-  mode_t mode;
+  mode_t mode, old;
+  char *s, *ss;
 
   if (!dirtree_notdotdot(try)) return 0;
 
@@ -51,11 +61,18 @@ static int do_chmod(struct dirtree *try)
     // but that's what you asked for in that case.
   } else {
     mode = string_to_mode(TT.mode, try->st.st_mode) & ~S_IFMT;
-    if (FLAG(v)) {
-      char *s = dirtree_path(try, 0);
-
-      printf("chmod '%s' to %s\n", s, TT.mode);
-      free(s);
+    if (FLAG(v)||FLAG(c)) {
+      mode_to_string(old = try->st.st_mode&07777, ss = toybuf+64);
+      *toybuf = 0;
+      if (old!=mode)
+        sprintf(toybuf, "changed from %04o (%s) to", old, ss+(*ss=='-'));
+      else if (FLAG(v)) strcpy(toybuf, "retained as");
+      if (*toybuf) {
+        s = dirtree_path(try, 0);
+        mode_to_string(mode, ss);
+        printf("mode of '%s' %s %04o (%s)\n", s, toybuf, mode, ss+(*ss=='-'));
+        free(s);
+      }
     }
     wfchmodat(dirtree_parentfd(try), try->name, mode);
   }
@@ -68,5 +85,13 @@ void chmod_main(void)
   TT.mode = *toys.optargs;
   char **file;
 
+  // -f means discard stderr, so replace it with the read end of a pipe
+  if (FLAG(f)) {
+    int pp[2];
+
+    pipe(pp);
+    dup2(*pp, 2);
+  }
+
   for (file = toys.optargs+1; *file; file++) dirtree_read(*file, do_chmod);
 }
-- 
2.39.5