printenv: exit status is 2 on failure

This provides a reliable and portable way to
test whether an environment variable is defined.

(Of course, if you are using glibc you may get
false positives if you include a = in the query.)

Signed-off-by: Mattias Andrée <maandree@kth.se>

printenv.1

@@ -1,4 +1,4 @@
-.Dd 2015-10-08
+.Dd 2016-03-30
 .Dt PRINTENV 1
 .Os sbase
 .Sh NAME
@@ -16,5 +16,14 @@ is given. Otherwise,
 prints only the value of each
 .Ar var
 one per line in the order specified.
+.SH EXIT STATUS
+.Bl -tag -width Ds
+.It 0
+Successful completion.
+.It 1
+One or more queried variables were not found.
+.It > 1
+An error occurred.
+.El
 .Sh SEE ALSO
 .Xr env 1

printenv.c

@@ -26,5 +26,5 @@ main(int argc, char *argv[])
 		}
 	}
 
-	return fshut(stdout, "<stdout>") || ret;
+	return fshut(stdout, "<stdout>") ? 2 : ret;
 }