find: Allow '/' to be used with -perm for GNU compatibility

In 2005, Gnu find deprecated '+' as the leading character for the -perm
argument, instead preferring '/' with the same meaning. Implement that
behavior here, and document it in the man page.

Reviewed by: imp, emaste
Pull Request: https://github.com/freebsd/freebsd-src/pull/1060

usr.bin/find/find.1

@@ -28,7 +28,7 @@
 .\" OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 .\" SUCH DAMAGE.
 .\"
-.Dd December 22, 2023
+.Dd January 15, 2024
 .Dt FIND 1
 .Os
 .Sh NAME
@@ -757,7 +757,7 @@ Slashes
 .Pq Dq Li /
 are treated as normal characters and do not have to be
 matched explicitly.
-.It Ic -perm Oo Cm - Ns | Ns Cm + Oc Ns Ar mode
+.It Ic -perm Oo Cm - Ns | Ns Cm + Ns | Ns Cm / Oc Ns Ar mode
 The
 .Ar mode
 may be either symbolic (see
@@ -786,11 +786,14 @@ are set in the file's mode bits.
 If the
 .Ar mode
 is preceded by a plus
-.Pq Dq Li + ,
+.Pq Dq Li +
 this primary evaluates to true
 if any of the bits in the
 .Ar mode
 are set in the file's mode bits.
+A slash
+.Pq Dq Li /
+is also accepted with the same meaning as plus for compatibility with GNU find.
 Otherwise, this primary evaluates to true if
 the bits in the
 .Ar mode
@@ -1116,6 +1119,16 @@ option was inspired by the equivalent
 and
 .Xr sed 1
 options.
+.Pp
+The
+.Ic -perm
+primary accepts a leading slash
+.Pq Dq Li /
+as an alias for a leading plus
+.Pq Dq Li +
+for its argument as an extension of
+.St -p1003.1-2001
+to be compatible with GNU find.
 .Sh HISTORY
 A simple
 .Nm

usr.bin/find/function.c

@@ -1338,7 +1338,7 @@ c_perm(OPTION *option, char ***argvp)
 	if (*perm == '-') {
 		new->flags |= F_ATLEAST;
 		++perm;
-	} else if (*perm == '+') {
+	} else if (*perm == '+' || *perm == '/') {
 		new->flags |= F_ANY;
 		++perm;
 	}