Use warn() instead of perror().

usr.bin/checknr/checknr.c

@@ -53,6 +53,7 @@ __FBSDID("$FreeBSD$");
  * later but for now think of these restrictions as contributions to
  * structured typesetting.
  */
+#include <err.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -257,7 +258,7 @@ main(int argc, char **argv)
 			cfilename = argv[i];
 			f = fopen(cfilename, "r");
 			if (f == NULL)
-				perror(cfilename);
+				warn("%s", cfilename);
 			else {
 				process(f);
 				fclose(f);

usr.bin/fmt/fmt.c

@@ -362,7 +362,7 @@ main(int argc, char *argv[]) {
 static void
 process_named_file(const char *name) {
   FILE *f=fopen(name, "r");
-  if (!f) { perror(name); ++n_errors; }
+  if (!f) { warn("%s", name); ++n_errors; }
   else {
     process_stream(f, name);
     fclose(f);
@@ -459,7 +459,7 @@ process_stream(FILE *stream, const char *name) {
     ++para_line_number;
   }
   new_paragraph(output_in_paragraph ? last_indent : first_indent, 0);
-  if (ferror(stream)) { perror(name); ++n_errors; }
+  if (ferror(stream)) { warn("%s", name); ++n_errors; }
 }
 
 /* How long is the indent on this line?
@@ -586,7 +586,7 @@ center_stream(FILE *stream, const char *name) {
     fwrite(line, 1, length, stdout);
     putchar('\n');
   }
-  if (ferror(stream)) { perror(name); ++n_errors; }
+  if (ferror(stream)) { warn("%s", name); ++n_errors; }
 }
 
 /* Get a single line from a stream. Expand tabs, strip control