Try to be clearer about which are the input and output files in

export mode.

doc/visudo.cat

@@ -4,7 +4,7 @@ NNAAMMEE
      vviissuuddoo - edit the sudoers file
 
 SSYYNNOOPPSSIISS
-     vviissuuddoo [--cchhqqssVV] [--ff _s_u_d_o_e_r_s] [--xx _f_i_l_e]
+     vviissuuddoo [--cchhqqssVV] [--ff _s_u_d_o_e_r_s] [--xx _o_u_t_p_u_t___f_i_l_e]
 
 DDEESSCCRRIIPPTTIIOONN
      vviissuuddoo edits the _s_u_d_o_e_r_s file in a safe fashion, analogous to vipw(1m).
@@ -72,14 +72,16 @@ DDEESSCCRRIIPPTTIIOONN
      --VV, ----vveerrssiioonn
                  Print the vviissuuddoo and _s_u_d_o_e_r_s grammar versions and exit.
 
-     --xx _f_i_l_e, ----eexxppoorrtt=_f_i_l_e
+     --xx _o_u_t_p_u_t___f_i_l_e, ----eexxppoorrtt=_o_u_t_p_u_t___f_i_l_e
-                 Export _s_u_d_o_e_r_s in JSON format and write it to _f_i_l_e.  If _f_i_l_e
+                 Export a _s_u_d_o_e_r_s in JSON format and write it to _o_u_t_p_u_t___f_i_l_e.
-                 is `-', the exported _s_u_d_o_e_r_s policy will be written to the
+                 If _o_u_t_p_u_t___f_i_l_e is `-', the exported _s_u_d_o_e_r_s policy will be
-                 standard output.  The exported format is intended to be
+                 written to the standard output.  By default, _/_e_t_c_/_s_u_d_o_e_r_s
-                 easier for third-party applications to parse than the
+                 (and any files it includes) will be exported.  The --ff option
-                 traditional _s_u_d_o_e_r_s format.  The various values have explicit
+                 can be used to specify a different _s_u_d_o_e_r_s file to export.
-                 types which removes much of the ambiguity of the _s_u_d_o_e_r_s
+                 The exported format is intended to be easier for third-party
-                 format.
+                 applications to parse than the traditional _s_u_d_o_e_r_s format.
+                 The various values have explicit types which removes much of
+                 the ambiguity of the _s_u_d_o_e_r_s format.
 
 EENNVVIIRROONNMMEENNTT
      The following environment variables may be consulted depending on the
@@ -123,6 +125,10 @@ DDIIAAGGNNOOSSTTIICCSS
            only a warning by default as ssuuddoo will ignore cycles when parsing
            the _s_u_d_o_e_r_s file.
 
+     visudo: /etc/sudoers: input and output files must be different
+           The --xx flag was used and the specified _o_u_t_p_u_t___f_i_l_e has the same
+           path name as the _s_u_d_o_e_r_s file to export.
+
 SSEEEE AALLSSOO
      vi(1), sudoers(4), sudo(1m), vipw(1m)
 
@@ -156,4 +162,4 @@ DDIISSCCLLAAIIMMEERR
      file distributed with ssuuddoo or http://www.sudo.ws/sudo/license.html for
      complete details.
 
-Sudo 1.8.10                    February 15, 2014                   Sudo 1.8.10
+Sudo 1.8.10                      May 13, 2014                      Sudo 1.8.10

doc/visudo.man.in

@@ -21,7 +21,7 @@
 .\" Agency (DARPA) and Air Force Research Laboratory, Air Force
 .\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
 .\"
-.TH "VISUDO" "@mansectsu@" "February 15, 2014" "Sudo @PACKAGE_VERSION@" "System Manager's Manual"
+.TH "VISUDO" "@mansectsu@" "May 13, 2014" "Sudo @PACKAGE_VERSION@" "System Manager's Manual"
 .nh
 .if n .ad l
 .SH "NAME"
@@ -32,7 +32,7 @@
 \fBvisudo\fR
 [\fB\-chqsV\fR]
 [\fB\-f\fR\ \fIsudoers\fR]
-[\fB\-x\fR\ \fIfile\fR]
+[\fB\-x\fR\ \fIoutput_file\fR]
 .SH "DESCRIPTION"
 \fBvisudo\fR
 edits the
@@ -205,18 +205,26 @@ and
 \fIsudoers\fR
 grammar versions and exit.
 .TP 12n
-\fB\-x\fR \fIfile\fR, \fB\--export\fR=\fIfile\fR
+\fB\-x\fR \fIoutput_file\fR, \fB\--export\fR=\fIoutput_file\fR
-Export
+Export a
 \fIsudoers\fR
 in JSON format and write it to
-\fIfile\fR.
+\fIoutput_file\fR.
 If
-\fIfile\fR
+\fIoutput_file\fR
 is
 \(oq-\(cq,
 the exported
 \fIsudoers\fR
 policy will be written to the standard output.
+By default,
+\fI@sysconfdir@/sudoers\fR
+(and any files it includes) will be exported.
+The
+\fB\-f\fR
+option can be used to specify a different
+\fIsudoers\fR
+file to export.
 The exported format is intended to be easier for third-party
 applications to parse than the traditional
 \fIsudoers\fR
@@ -298,6 +306,15 @@ will ignore cycles when parsing
 the
 \fIsudoers\fR
 file.
+.TP 6n
+\fRvisudo: @sysconfdir@/sudoers: input and output files must be different\fR
+The
+\fB\-x\fR
+flag was used and the specified
+\fIoutput_file\fR
+has the same path name as the
+\fIsudoers\fR
+file to export.
 .SH "SEE ALSO"
 vi(1),
 sudoers(@mansectform@),

doc/visudo.mdoc.in

@@ -19,7 +19,7 @@
 .\" Agency (DARPA) and Air Force Research Laboratory, Air Force
 .\" Materiel Command, USAF, under agreement number F39502-99-1-0512.
 .\"
-.Dd February 15, 2014
+.Dd May 13, 2014
 .Dt VISUDO @mansectsu@
 .Os Sudo @PACKAGE_VERSION@
 .Sh NAME
@@ -29,7 +29,7 @@
 .Nm visudo
 .Op Fl chqsV
 .Op Fl f Ar sudoers
-.Op Fl x Ar file
+.Op Fl x Ar output_file
 .Sh DESCRIPTION
 .Nm visudo
 edits the
@@ -196,18 +196,26 @@ Print the
 and
 .Em sudoers
 grammar versions and exit.
-.It Fl x Ar file , Fl -export Ns = Ns Ar file
+.It Fl x Ar output_file , Fl -export Ns = Ns Ar output_file
-Export
+Export a
 .Em sudoers
 in JSON format and write it to
-.Ar file .
+.Ar output_file .
 If
-.Ar file
+.Ar output_file
 is
 .Ql - ,
 the exported
 .Em sudoers
 policy will be written to the standard output.
+By default,
+.Pa @sysconfdir@/sudoers
+(and any files it includes) will be exported.
+The
+.Fl f
+option can be used to specify a different
+.Em sudoers
+file to export.
 The exported format is intended to be easier for third-party
 applications to parse than the traditional
 .Em sudoers
@@ -286,6 +294,14 @@ will ignore cycles when parsing
 the
 .Em sudoers
 file.
+.It Li visudo: @sysconfdir@/sudoers: input and output files must be different
+The
+.Fl x
+flag was used and the specified
+.Ar output_file
+has the same path name as the
+.Em sudoers
+file to export.
 .El
 .Sh SEE ALSO
 .Xr vi 1 ,

plugins/sudoers/visudo.c

@@ -1318,7 +1318,7 @@ static void
 usage(int fatal)
 {
     (void) fprintf(fatal ? stderr : stdout,
-	"usage: %s [-chqsV] [-f sudoers] [-x file]\n", getprogname());
+	"usage: %s [-chqsV] [-f sudoers] [-x output_file]\n", getprogname());
     if (fatal)
 	exit(1);
 }
@@ -1329,12 +1329,12 @@ help(void)
     (void) printf(_("%s - safely edit the sudoers file\n\n"), getprogname());
     usage(0);
     (void) puts(_("\nOptions:\n"
-	"  -c, --check       check-only mode\n"
+	"  -c, --check              check-only mode\n"
-	"  -f, --file=file   specify sudoers file location\n"
+	"  -f, --file=sudoers       specify sudoers file location\n"
-	"  -h, --help        display help message and exit\n"
+	"  -h, --help               display help message and exit\n"
-	"  -q, --quiet       less verbose (quiet) syntax error messages\n"
+	"  -q, --quiet              less verbose (quiet) syntax error messages\n"
-	"  -s, --strict      strict syntax checking\n"
+	"  -s, --strict             strict syntax checking\n"
-	"  -V, --version     display version information and exit\n"
+	"  -V, --version            display version information and exit\n"
-	"  -x, --export=file export sudoers in JSON format"));
+	"  -x, --export=output_file write sudoers in JSON format to output_file"));
     exit(0);
 }