diff --git a/c/cli/mlrcli.c b/c/cli/mlrcli.c
index 4f556b31e..2997da4fd 100644
--- a/c/cli/mlrcli.c
+++ b/c/cli/mlrcli.c
@@ -243,7 +243,8 @@ cli_opts_t* parse_command_line(int argc, char** argv) {
 		}
 
 		// It's up to the parse func to print its usage on CLI-parse failure.
-		mapper_t* pmapper = pmapper_setup->pparse_func(&argi, argc, argv);
+		mapper_t* pmapper = pmapper_setup->pparse_func(&argi, argc, argv,
+			&popts->reader_opts, &popts->writer_opts);
 		if (pmapper == NULL) {
 			exit(1);
 		}
diff --git a/c/cli/mlrcli.h b/c/cli/mlrcli.h
index ba12d3e2c..a21c8023f 100644
--- a/c/cli/mlrcli.h
+++ b/c/cli/mlrcli.h
@@ -11,7 +11,6 @@
 #include "containers/lhmsi.h"
 #include "containers/lhmss.h"
 #include "input/lrec_reader.h"
-#include "mapping/mapper.h"
 #include "output/lrec_writer.h"
 
 // ----------------------------------------------------------------
diff --git a/c/mapping/mapper.h b/c/mapping/mapper.h
index 622637a83..3f41af740 100644
--- a/c/mapping/mapper.h
+++ b/c/mapping/mapper.h
@@ -3,6 +3,7 @@
 
 #include <stdio.h>
 #include "lib/context.h"
+#include "cli/mlrcli.h"
 #include "containers/lrec.h"
 #include "containers/sllv.h"
 
@@ -28,7 +29,8 @@ typedef struct _mapper_t {
 // Control plane:
 
 typedef void mapper_usage_func_t(FILE* o, char* argv0, char* verb);
-typedef      mapper_t* mapper_parse_cli_func_t(int* pargi, int argc, char** argv);
+typedef      mapper_t* mapper_parse_cli_func_t(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* pmain_reader_opts, cli_writer_opts_t* pmain_writer_opts);
 
 typedef struct _mapper_setup_t {
 	char*                    verb;
diff --git a/c/mapping/mapper_bar.c b/c/mapping/mapper_bar.c
index af7af238f..19cb80fe2 100644
--- a/c/mapping/mapper_bar.c
+++ b/c/mapping/mapper_bar.c
@@ -20,7 +20,8 @@ typedef struct _mapper_bar_state_t {
 } mapper_bar_state_t;
 
 static void      mapper_bar_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_bar_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_bar_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_bar_alloc(ap_state_t* pargp, string_array_t* pfield_names,
 	char fill_char, char oob_char, char blank_char, double lo, double hi,
 	int width, int do_auto);
@@ -62,7 +63,9 @@ static void mapper_bar_usage(FILE* o, char* argv0, char* verb) {
 }
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_bar_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_bar_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	string_array_t*  pfield_names = NULL;
 	char*  fill_string  = NULL;
 	char*  oob_string   = NULL;
diff --git a/c/mapping/mapper_bootstrap.c b/c/mapping/mapper_bootstrap.c
index 4582b7857..fe7b81cdf 100644
--- a/c/mapping/mapper_bootstrap.c
+++ b/c/mapping/mapper_bootstrap.c
@@ -13,7 +13,8 @@ typedef struct _mapper_bootstrap_state_t {
 } mapper_bootstrap_state_t;
 
 static void      mapper_bootstrap_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_bootstrap_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_bootstrap_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_bootstrap_alloc(int nout, ap_state_t* pargp);
 static void      mapper_bootstrap_free(mapper_t* pmapper);
 static sllv_t*   mapper_bootstrap_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -35,7 +36,9 @@ static void mapper_bootstrap_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "See also %s sample and %s shuffle.\n", argv0, argv0);
 }
 
-static mapper_t* mapper_bootstrap_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_bootstrap_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	int nout = NOUT_EQUALS_NIN;
 	if ((argc - *pargi) < 1) {
 		mapper_bootstrap_usage(stderr, argv[0], argv[*pargi]);
diff --git a/c/mapping/mapper_cat.c b/c/mapping/mapper_cat.c
index 99fe54443..82ac8b93c 100644
--- a/c/mapping/mapper_cat.c
+++ b/c/mapping/mapper_cat.c
@@ -12,7 +12,8 @@ typedef struct _mapper_cat_state_t {
 #define DEFAULT_COUNTER_FIELD_NAME "n"
 
 static void      mapper_cat_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_cat_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_cat_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_cat_alloc(ap_state_t* pargp, int do_counters, char* counter_field_name);
 static void      mapper_cat_free(mapper_t* pmapper);
 static sllv_t*   mapper_cat_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -26,7 +27,9 @@ mapper_setup_t mapper_cat_setup = {
 };
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_cat_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_cat_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	char* default_counter_field_name = DEFAULT_COUNTER_FIELD_NAME;
 	char* counter_field_name = NULL;
 	int   do_counters = FALSE;
diff --git a/c/mapping/mapper_check.c b/c/mapping/mapper_check.c
index 3e4443958..7405eff73 100644
--- a/c/mapping/mapper_check.c
+++ b/c/mapping/mapper_check.c
@@ -3,7 +3,8 @@
 #include "containers/sllv.h"
 
 static void      mapper_check_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_check_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_check_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_check_alloc();
 static void      mapper_check_free(mapper_t* pmapper);
 static sllv_t*   mapper_check_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -22,7 +23,9 @@ static void mapper_check_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "Useful for doing a well-formatted check on input data.\n");
 }
 
-static mapper_t* mapper_check_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_check_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	if ((argc - *pargi) < 1) {
 		mapper_check_usage(stderr, argv[0], argv[*pargi]);
 		return NULL;
diff --git a/c/mapping/mapper_cut.c b/c/mapping/mapper_cut.c
index e687ac2e3..d58ea9441 100644
--- a/c/mapping/mapper_cut.c
+++ b/c/mapping/mapper_cut.c
@@ -18,7 +18,8 @@ typedef struct _mapper_cut_state_t {
 } mapper_cut_state_t;
 
 static void      mapper_cut_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_cut_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_cut_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_cut_alloc(ap_state_t* pargp, slls_t* pfield_name_list,
 	int do_arg_order, int do_complement, int do_regexes);
 static void      mapper_cut_free(mapper_t* pmapper);
@@ -53,7 +54,9 @@ static void mapper_cut_usage(FILE* o, char* argv0, char* verb) {
 }
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_cut_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_cut_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	slls_t* pfield_name_list  = NULL;
 	int     do_arg_order  = FALSE;
 	int     do_complement = FALSE;
diff --git a/c/mapping/mapper_decimate.c b/c/mapping/mapper_decimate.c
index 2f4276819..d2691c8fb 100644
--- a/c/mapping/mapper_decimate.c
+++ b/c/mapping/mapper_decimate.c
@@ -19,7 +19,8 @@ typedef struct _mapper_decimate_state_t {
 } mapper_decimate_state_t;
 
 static void      mapper_decimate_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_decimate_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_decimate_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_decimate_alloc(ap_state_t* pargp, slls_t* pgroup_by_field_names,
 	unsigned long long decimate_count, int keep_last);
 static void      mapper_decimate_free(mapper_t* pmapper);
@@ -42,7 +43,9 @@ static void mapper_decimate_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "Passes through one of every n records, optionally by category.\n");
 }
 
-static mapper_t* mapper_decimate_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_decimate_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	int     decimate_count = 10;
 	int     keep_last      = TRUE;
 	slls_t* pgroup_by_field_names = slls_alloc();
diff --git a/c/mapping/mapper_filter.c b/c/mapping/mapper_filter.c
index 669f1a020..ae0d0d2dc 100644
--- a/c/mapping/mapper_filter.c
+++ b/c/mapping/mapper_filter.c
@@ -20,7 +20,8 @@ typedef struct _mapper_filter_state_t {
 } mapper_filter_state_t;
 
 static void      mapper_filter_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_filter_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_filter_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_filter_alloc(ap_state_t* pargp, char* mlr_dsl_expression, char* comment_stripped_mlr_dsl_expression,
 	mlr_dsl_ast_node_t* past, int type_inferencing, int do_exclude);
 static void      mapper_filter_free(mapper_t* pmapper);
@@ -79,7 +80,9 @@ static void mapper_filter_usage(FILE* o, char* argv0, char* verb) {
 }
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_filter_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_filter_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	char* verb                                = argv[(*pargi)++];
 	char* mlr_dsl_expression                  = NULL;
 	char* comment_stripped_mlr_dsl_expression = NULL;
diff --git a/c/mapping/mapper_grep.c b/c/mapping/mapper_grep.c
index 0c929d109..ff68051f4 100644
--- a/c/mapping/mapper_grep.c
+++ b/c/mapping/mapper_grep.c
@@ -13,7 +13,8 @@ typedef struct _mapper_grep_state_t {
 } mapper_grep_state_t;
 
 static void      mapper_grep_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_grep_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_grep_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_grep_alloc(ap_state_t* pargp, char* regex_string, int exclude, int ignore_case);
 static void      mapper_grep_free(mapper_t* pmapper);
 static sllv_t*   mapper_grep_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -26,7 +27,9 @@ mapper_setup_t mapper_grep_setup = {
 };
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_grep_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_grep_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	char* regex_string = NULL;
 	int   exclude = FALSE;
 	int   ignore_case = FALSE;
diff --git a/c/mapping/mapper_group_like.c b/c/mapping/mapper_group_like.c
index 170f4f4d9..0b12d6ab5 100644
--- a/c/mapping/mapper_group_like.c
+++ b/c/mapping/mapper_group_like.c
@@ -14,7 +14,8 @@ typedef struct _mapper_group_like_state_t {
 } mapper_group_like_state_t;
 
 static void      mapper_group_like_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_group_like_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_group_like_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_group_like_alloc();
 static void      mapper_group_like_free(mapper_t* pmapper);
 static sllv_t*   mapper_group_like_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -32,7 +33,9 @@ static void mapper_group_like_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "Outputs records in batches having identical field names.\n");
 }
 
-static mapper_t* mapper_group_like_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_group_like_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	if ((argc - *pargi) < 1) {
 		mapper_group_like_usage(stderr, argv[0], argv[*pargi]);
 		return NULL;
diff --git a/c/mapping/mapper_having_fields.c b/c/mapping/mapper_having_fields.c
index 1115ba474..b97b148d8 100644
--- a/c/mapping/mapper_having_fields.c
+++ b/c/mapping/mapper_having_fields.c
@@ -25,7 +25,8 @@ typedef struct _mapper_having_fields_state_t {
 } mapper_having_fields_state_t;
 
 static void      mapper_having_fields_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_having_fields_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_having_fields_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 
 static mapper_t* mapper_having_fields_alloc(slls_t* pfield_names, char* regex_string, criterion_t criterion);
 static void      mapper_having_fields_free(mapper_t* pmapper);
@@ -64,7 +65,9 @@ static void mapper_having_fields_usage(FILE* o, char* argv0, char* verb) {
 }
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_having_fields_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_having_fields_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	slls_t*     pfield_names = NULL;
 	char*       regex_string = NULL;
 	criterion_t criterion    = HAVING_FIELDS_UNSPECIFIED;
diff --git a/c/mapping/mapper_head.c b/c/mapping/mapper_head.c
index 8242a6983..7694e7c3f 100644
--- a/c/mapping/mapper_head.c
+++ b/c/mapping/mapper_head.c
@@ -19,7 +19,8 @@ typedef struct _mapper_head_state_t {
 } mapper_head_state_t;
 
 static void      mapper_head_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_head_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_head_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_head_alloc(ap_state_t* pargp, slls_t* pgroup_by_field_names, unsigned long long head_count);
 static void      mapper_head_free(mapper_t* pmapper);
 static sllv_t*   mapper_head_process_unkeyed(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -42,7 +43,9 @@ static void mapper_head_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "records have been read.\n");
 }
 
-static mapper_t* mapper_head_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_head_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	int     head_count            = 10;
 	slls_t* pgroup_by_field_names = slls_alloc();
 
diff --git a/c/mapping/mapper_histogram.c b/c/mapping/mapper_histogram.c
index ffea00724..724494688 100644
--- a/c/mapping/mapper_histogram.c
+++ b/c/mapping/mapper_histogram.c
@@ -26,7 +26,8 @@ typedef struct _mapper_histogram_state_t {
 } mapper_histogram_state_t;
 
 static void      mapper_histogram_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_histogram_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_histogram_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_histogram_alloc(ap_state_t* pargp, slls_t* value_field_names, double lo, int nbins, double hi,
 	int do_auto);
 static void      mapper_histogram_free(mapper_t* pmapper);
@@ -58,7 +59,9 @@ static void mapper_histogram_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "Just a histogram. Input values < lo or > hi are not counted.\n");
 }
 
-static mapper_t* mapper_histogram_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_histogram_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	slls_t* value_field_names = NULL;
 	double lo = 0.0;
 	double hi = 0.0;
diff --git a/c/mapping/mapper_join.c b/c/mapping/mapper_join.c
index 40727a277..d49078a14 100644
--- a/c/mapping/mapper_join.c
+++ b/c/mapping/mapper_join.c
@@ -49,7 +49,8 @@ typedef struct _mapper_join_state_t {
 
 // ----------------------------------------------------------------
 static void mapper_join_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_join_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_join_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_join_alloc(mapper_join_opts_t* popts);
 static void mapper_join_free(mapper_t* pmapper);
 static void ingest_left_file(mapper_join_state_t* pstate);
@@ -111,7 +112,9 @@ static void mapper_join_usage(FILE* o, char* argv0, char* verb) {
 }
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_join_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_join_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	mapper_join_opts_t* popts = mlr_malloc_or_die(sizeof(mapper_join_opts_t));
 
 	cli_reader_opts_init(&popts->reader_opts);
diff --git a/c/mapping/mapper_label.c b/c/mapping/mapper_label.c
index f99ec2afb..43a96fa64 100644
--- a/c/mapping/mapper_label.c
+++ b/c/mapping/mapper_label.c
@@ -8,7 +8,8 @@ typedef struct _mapper_label_state_t {
 } mapper_label_state_t;
 
 static void      mapper_label_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_label_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_label_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_label_alloc(slls_t* pnames);
 static void      mapper_label_free(mapper_t* pmapper);
 static sllv_t*   mapper_label_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -33,7 +34,9 @@ static void mapper_label_usage(FILE* o, char* argv0, char* verb) {
 
 }
 
-static mapper_t* mapper_label_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_label_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	if ((argc - *pargi) < 2) {
 		mapper_label_usage(stderr, argv[0], argv[*pargi]);
 		return NULL;
diff --git a/c/mapping/mapper_merge_fields.c b/c/mapping/mapper_merge_fields.c
index ca0550982..c185100aa 100644
--- a/c/mapping/mapper_merge_fields.c
+++ b/c/mapping/mapper_merge_fields.c
@@ -56,7 +56,8 @@ typedef struct _mapper_merge_fields_state_t {
 
 // ----------------------------------------------------------------
 static void      mapper_merge_fields_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_merge_fields_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_merge_fields_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_merge_fields_alloc(slls_t* paccumulator_names, merge_by_t do_which,
 	slls_t* pvalue_field_names, char* output_field_basename, int allow_int_float, int do_interpolated_percentiles,
 	int keep_input_fields);
@@ -105,7 +106,9 @@ static void mapper_merge_fields_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "  \"b_y\", and \"b_out_x\" collapses to \"b_x\".\n");
 }
 
-static mapper_t* mapper_merge_fields_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_merge_fields_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	slls_t*    paccumulator_names          = NULL;
 	slls_t*    pvalue_field_names          = NULL;
 	char*      output_field_basename       = NULL;
diff --git a/c/mapping/mapper_nest.c b/c/mapping/mapper_nest.c
index a55f0c0e6..03c8cd2a8 100644
--- a/c/mapping/mapper_nest.c
+++ b/c/mapping/mapper_nest.c
@@ -31,7 +31,8 @@ typedef struct _nest_bucket_t {
 } nest_bucket_t;
 
 static void      mapper_nest_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_nest_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_nest_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_nest_alloc(ap_state_t* pargp, char* argv0,
 	char* field_name, char* nested_fs, char* nested_ps,
 	int do_explode, int do_pairs, int do_across_fields);
@@ -110,7 +111,9 @@ static void mapper_nest_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "See also %s reshape.\n", argv0);
 }
 
-static mapper_t* mapper_nest_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_nest_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	char* field_name = NULL;
 	char* nested_fs = ";";
 	char* nested_ps = ":";
diff --git a/c/mapping/mapper_nothing.c b/c/mapping/mapper_nothing.c
index 5f85c6c95..44ffe35cb 100644
--- a/c/mapping/mapper_nothing.c
+++ b/c/mapping/mapper_nothing.c
@@ -4,7 +4,8 @@
 #include "containers/sllv.h"
 
 static void      mapper_nothing_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_nothing_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_nothing_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_nothing_alloc();
 static void      mapper_nothing_free(mapper_t* pmapper);
 static sllv_t*   mapper_nothing_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -17,7 +18,9 @@ mapper_setup_t mapper_nothing_setup = {
 };
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_nothing_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_nothing_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	if ((argc - *pargi) < 1) {
 		mapper_nothing_usage(stderr, argv[0], argv[*pargi]);
 		return NULL;
diff --git a/c/mapping/mapper_put.c b/c/mapping/mapper_put.c
index d4a45e853..ce210adec 100644
--- a/c/mapping/mapper_put.c
+++ b/c/mapping/mapper_put.c
@@ -33,7 +33,8 @@ typedef struct _mapper_put_state_t {
 } mapper_put_state_t;
 
 static void      mapper_put_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_put_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_put_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_put_alloc(char* mlr_dsl_expression, char* comment_stripped_mlr_dsl_expression,
 	mlr_dsl_ast_t* past, int outer_filter, int type_inferencing, char* oosvar_flatten_separator,
 	int flush_every_record, cli_writer_opts_t* pwriter_opts);
@@ -113,7 +114,9 @@ static void mapper_put_usage(FILE* o, char* argv0, char* verb) {
 }
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_put_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_put_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	char* mlr_dsl_expression                  = NULL;
 	char* comment_stripped_mlr_dsl_expression = NULL;
 	char* expression_filename                 = NULL;
diff --git a/c/mapping/mapper_regularize.c b/c/mapping/mapper_regularize.c
index d7203ba84..676ddbbb3 100644
--- a/c/mapping/mapper_regularize.c
+++ b/c/mapping/mapper_regularize.c
@@ -9,7 +9,8 @@ typedef struct _mapper_regularize_state_t {
 } mapper_regularize_state_t;
 
 static void      mapper_regularize_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_regularize_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_regularize_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_regularize_alloc();
 static void      mapper_regularize_free(mapper_t* pmapper);
 static sllv_t*   mapper_regularize_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -31,7 +32,9 @@ static void mapper_regularize_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "output as              a=1,c=2,b=3, then e=4,d=5, then a=6,c=7,b=8\n");
 }
 
-static mapper_t* mapper_regularize_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_regularize_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	*pargi += 1;
 	return mapper_regularize_alloc();
 }
diff --git a/c/mapping/mapper_rename.c b/c/mapping/mapper_rename.c
index 0f6c9bdae..aa5244ab2 100644
--- a/c/mapping/mapper_rename.c
+++ b/c/mapping/mapper_rename.c
@@ -22,7 +22,8 @@ typedef struct _mapper_rename_state_t {
 } mapper_rename_state_t;
 
 static void      mapper_rename_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_rename_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_rename_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_rename_alloc(ap_state_t* pargp, lhmss_t* pold_to_new, int do_regexes, int do_gsub);
 static void      mapper_rename_free(mapper_t* pmapper);
 static sllv_t*   mapper_rename_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -59,7 +60,9 @@ static void mapper_rename_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "%s %s -r '\"name\"i,Name'       Rename \"name\", \"Name\", \"NAME\", etc. to \"Name\"\n", argv0, verb);
 }
 
-static mapper_t* mapper_rename_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_rename_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	int do_regexes = FALSE;
 	int do_gsub = FALSE;
 
diff --git a/c/mapping/mapper_reorder.c b/c/mapping/mapper_reorder.c
index 46a187f5c..f85710e55 100644
--- a/c/mapping/mapper_reorder.c
+++ b/c/mapping/mapper_reorder.c
@@ -12,7 +12,8 @@ typedef struct _mapper_reorder_state_t {
 } mapper_reorder_state_t;
 
 static void      mapper_reorder_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_reorder_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_reorder_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_reorder_alloc(ap_state_t* pargp, slls_t* pfield_name_list, int put_at_end);
 static void      mapper_reorder_free(mapper_t* pmapper);
 static sllv_t*   mapper_reorder_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -38,7 +39,9 @@ static void mapper_reorder_usage(FILE* o, char* argv0, char* verb) {
 }
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_reorder_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_reorder_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	slls_t* pfield_name_list = NULL;
 	int     put_at_end       = FALSE;
 
diff --git a/c/mapping/mapper_repeat.c b/c/mapping/mapper_repeat.c
index d70b0ba28..c9ed5f1d8 100644
--- a/c/mapping/mapper_repeat.c
+++ b/c/mapping/mapper_repeat.c
@@ -22,7 +22,8 @@ typedef struct _mapper_repeat_state_t {
 } mapper_repeat_state_t;
 
 static void      mapper_repeat_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_repeat_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_repeat_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_repeat_alloc(ap_state_t* pargp, long long repeat_count, char* repeat_count_field_name);
 static void      mapper_repeat_free(mapper_t* pmapper);
 static sllv_t*   mapper_repeat_process_nop(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -65,7 +66,9 @@ static void mapper_repeat_usage(FILE* o, char* argv0, char* verb) {
 }
 
 static const long long UNINIT_REPEAT_COUNT = -123457689LL;
-static mapper_t* mapper_repeat_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_repeat_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	long long repeat_count = UNINIT_REPEAT_COUNT;
 	char* repeat_count_field_name = NULL;
 
diff --git a/c/mapping/mapper_reshape.c b/c/mapping/mapper_reshape.c
index 7098b6e16..e1f661b0e 100644
--- a/c/mapping/mapper_reshape.c
+++ b/c/mapping/mapper_reshape.c
@@ -57,7 +57,8 @@ typedef struct _reshape_bucket_t {
 } reshape_bucket_t;
 
 static void      mapper_reshape_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_reshape_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_reshape_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_reshape_alloc(
 	ap_state_t* pargp,
 	slls_t* input_field_names,
@@ -140,7 +141,9 @@ static void mapper_reshape_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "See also %s nest.\n", argv0);
 }
 
-static mapper_t* mapper_reshape_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_reshape_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	slls_t* input_field_names         = NULL;
 	slls_t* input_field_regex_strings = NULL;
 	slls_t* output_field_names        = NULL;
diff --git a/c/mapping/mapper_sample.c b/c/mapping/mapper_sample.c
index dd9d8a19a..e56694916 100644
--- a/c/mapping/mapper_sample.c
+++ b/c/mapping/mapper_sample.c
@@ -32,7 +32,8 @@ typedef struct _mapper_sample_state_t {
 } mapper_sample_state_t;
 
 static void      mapper_sample_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_sample_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_sample_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_sample_alloc(ap_state_t* pargp, slls_t* pgroup_by_field_names,
 	unsigned long long sample_count);
 static void      mapper_sample_free(mapper_t* pmapper);
@@ -54,7 +55,9 @@ static void mapper_sample_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "See also %s bootstrap and %s shuffle.\n", argv0, argv0);
 }
 
-static mapper_t* mapper_sample_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_sample_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	int     sample_count          = -1;
 	slls_t* pgroup_by_field_names = slls_alloc();
 
diff --git a/c/mapping/mapper_sec2gmt.c b/c/mapping/mapper_sec2gmt.c
index 1b344a6d2..62093db4f 100644
--- a/c/mapping/mapper_sec2gmt.c
+++ b/c/mapping/mapper_sec2gmt.c
@@ -10,7 +10,8 @@ typedef struct _mapper_sec2gmt_state_t {
 } mapper_sec2gmt_state_t;
 
 static void      mapper_sec2gmt_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_sec2gmt_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_sec2gmt_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_sec2gmt_alloc(slls_t* pfield_names);
 static void      mapper_sec2gmt_free(mapper_t* pmapper);
 static sllv_t*   mapper_sec2gmt_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -34,7 +35,9 @@ static void mapper_sec2gmt_usage(FILE* o, char* argv0, char* verb) {
 }
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_sec2gmt_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_sec2gmt_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	if ((argc - *pargi) < 2) {
 		mapper_sec2gmt_usage(stderr, argv[0], argv[*pargi]);
 		return NULL;
diff --git a/c/mapping/mapper_sec2gmtdate.c b/c/mapping/mapper_sec2gmtdate.c
index 4e2cbee93..4e9d5c246 100644
--- a/c/mapping/mapper_sec2gmtdate.c
+++ b/c/mapping/mapper_sec2gmtdate.c
@@ -10,7 +10,8 @@ typedef struct _mapper_sec2gmtdate_state_t {
 } mapper_sec2gmtdate_state_t;
 
 static void      mapper_sec2gmtdate_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_sec2gmtdate_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_sec2gmtdate_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_sec2gmtdate_alloc(slls_t* pfield_names);
 static void      mapper_sec2gmtdate_free(mapper_t* pmapper);
 static sllv_t*   mapper_sec2gmtdate_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -34,7 +35,9 @@ static void mapper_sec2gmtdate_usage(FILE* o, char* argv0, char* verb) {
 }
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_sec2gmtdate_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_sec2gmtdate_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	if ((argc - *pargi) < 2) {
 		mapper_sec2gmtdate_usage(stderr, argv[0], argv[*pargi]);
 		return NULL;
diff --git a/c/mapping/mapper_shuffle.c b/c/mapping/mapper_shuffle.c
index 59c45b3c4..79fa53f79 100644
--- a/c/mapping/mapper_shuffle.c
+++ b/c/mapping/mapper_shuffle.c
@@ -19,7 +19,8 @@ typedef struct _mapper_shuffle_state_t {
 } mapper_shuffle_state_t;
 
 static void      mapper_shuffle_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_shuffle_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_shuffle_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_shuffle_alloc(ap_state_t* pargp);
 static void      mapper_shuffle_free(mapper_t* pmapper);
 static sllv_t*   mapper_shuffle_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -39,7 +40,9 @@ static void mapper_shuffle_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "See also %s bootstrap and %s sample.\n", argv0, argv0);
 }
 
-static mapper_t* mapper_shuffle_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_shuffle_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	char* verb = argv[(*pargi)++];
 
 	ap_state_t* pstate = ap_alloc();
diff --git a/c/mapping/mapper_sort.c b/c/mapping/mapper_sort.c
index 5eec005f3..1f40a9b71 100644
--- a/c/mapping/mapper_sort.c
+++ b/c/mapping/mapper_sort.c
@@ -79,9 +79,11 @@ typedef struct _sort_bucket_t {
 
 // ----------------------------------------------------------------
 static void      mapper_sort_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_sort_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_sort_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static void      mapper_group_by_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_group_by_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_group_by_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_sort_alloc(slls_t* pkey_field_names, int* sort_params, int do_sort);
 static void      mapper_sort_free(mapper_t* pmapper);
 static sllv_t*   mapper_sort_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -129,7 +131,9 @@ static void mapper_sort_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "  %s %s -f a -f b -nr x -nr y -nr z\n", argv0, verb);
 }
 
-static mapper_t* mapper_sort_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_sort_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	if ((argc - *pargi) < 3) {
 		mapper_sort_usage(stderr, argv[0], argv[*pargi]);
 		return NULL;
@@ -192,7 +196,9 @@ static void mapper_group_by_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "Outputs records in batches having identical values at specified field names.\n");
 }
 
-static mapper_t* mapper_group_by_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_group_by_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	if ((argc - *pargi) < 2) {
 		mapper_group_by_usage(stderr, argv[0], argv[*pargi]);
 		return NULL;
diff --git a/c/mapping/mapper_stats1.c b/c/mapping/mapper_stats1.c
index 56e47976e..e8e72c8bb 100644
--- a/c/mapping/mapper_stats1.c
+++ b/c/mapping/mapper_stats1.c
@@ -30,7 +30,8 @@ typedef struct _mapper_stats1_state_t {
 } mapper_stats1_state_t;
 
 static void      mapper_stats1_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_stats1_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_stats1_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_stats1_alloc(ap_state_t* pargp, slls_t* paccumulator_names, string_array_t* pvalue_field_names,
 	slls_t* pgroup_by_field_names, int do_iterative_stats, int allow_int_float, int do_interpolated_percentiles);
 static void      mapper_stats1_free(mapper_t* pmapper);
@@ -82,7 +83,9 @@ static void mapper_stats1_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "* When there are mode ties, the first-encountered datum wins.\n");
 }
 
-static mapper_t* mapper_stats1_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_stats1_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	slls_t*         paccumulator_names          = NULL;
 	string_array_t* pvalue_field_names          = NULL;
 	slls_t*         pgroup_by_field_names       = slls_alloc();
diff --git a/c/mapping/mapper_stats2.c b/c/mapping/mapper_stats2.c
index 050f6ac98..9a43dd42a 100644
--- a/c/mapping/mapper_stats2.c
+++ b/c/mapping/mapper_stats2.c
@@ -55,7 +55,8 @@ typedef stats2_acc_t* stats2_alloc_func_t(char* value_field_name_1, char* value_
 
 // ----------------------------------------------------------------
 static void      mapper_stats2_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_stats2_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_stats2_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_stats2_alloc(ap_state_t* pargp, slls_t* paccumulator_names,
 	string_array_t* pvalue_field_name_pairs, slls_t* pgroup_by_field_names,
 	int do_verbose, int do_iterative_stats, int do_hold_and_fit);
@@ -127,7 +128,9 @@ static void mapper_stats2_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "Example: %s %s -a corr -f x,y\n", argv0, verb);
 }
 
-static mapper_t* mapper_stats2_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_stats2_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	slls_t*         paccumulator_names    = NULL;
 	string_array_t* pvalue_field_names    = NULL;
 	slls_t*         pgroup_by_field_names = slls_alloc();
diff --git a/c/mapping/mapper_step.c b/c/mapping/mapper_step.c
index fc720f78b..2efee95db 100644
--- a/c/mapping/mapper_step.c
+++ b/c/mapping/mapper_step.c
@@ -73,7 +73,8 @@ typedef struct _mapper_step_state_t {
 
 // ----------------------------------------------------------------
 static void      mapper_step_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_step_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_step_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_step_alloc(ap_state_t* pargp, slls_t* pstepper_names, string_array_t* pvalue_field_names,
 	slls_t* pgroup_by_field_names, int allow_int_float, slls_t* pstring_alphas, slls_t* pewma_suffixes);
 static void      mapper_step_free(mapper_t* pmapper);
@@ -149,7 +150,9 @@ static void mapper_step_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "for more information on EWMA.\n");
 }
 
-static mapper_t* mapper_step_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_step_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	slls_t*         pstepper_names        = NULL;
 	string_array_t* pvalue_field_names    = NULL;
 	slls_t*         pgroup_by_field_names = slls_alloc();
diff --git a/c/mapping/mapper_tac.c b/c/mapping/mapper_tac.c
index e89dc9824..dfd589668 100644
--- a/c/mapping/mapper_tac.c
+++ b/c/mapping/mapper_tac.c
@@ -8,7 +8,8 @@ typedef struct _mapper_tac_state_t {
 } mapper_tac_state_t;
 
 static void      mapper_tac_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_tac_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_tac_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_tac_alloc();
 static void      mapper_tac_free(mapper_t* pmapper);
 static sllv_t*   mapper_tac_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -26,7 +27,9 @@ static void mapper_tac_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "Prints records in reverse order from the order in which they were encountered.\n");
 }
 
-static mapper_t* mapper_tac_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_tac_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	if ((argc - *pargi) < 1) {
 		mapper_tac_usage(stderr, argv[0], argv[*pargi]);
 		return NULL;
diff --git a/c/mapping/mapper_tail.c b/c/mapping/mapper_tail.c
index 98d620135..e005b2ae3 100644
--- a/c/mapping/mapper_tail.c
+++ b/c/mapping/mapper_tail.c
@@ -19,7 +19,8 @@ typedef struct _mapper_tail_state_t {
 } mapper_tail_state_t;
 
 static void      mapper_tail_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_tail_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_tail_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_tail_alloc(ap_state_t* pargp, slls_t* pgroup_by_field_names, unsigned long long tail_count);
 static void      mapper_tail_free(mapper_t* pmapper);
 static sllv_t*   mapper_tail_process(lrec_t* pinrec, context_t* pctx, void* pvstate);
@@ -39,7 +40,9 @@ static void mapper_tail_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "Passes through the last n records, optionally by category.\n");
 }
 
-static mapper_t* mapper_tail_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_tail_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	int     tail_count            = 10;
 	slls_t* pgroup_by_field_names = slls_alloc();
 
diff --git a/c/mapping/mapper_tee.c b/c/mapping/mapper_tee.c
index 65ad43714..5f21c7f52 100644
--- a/c/mapping/mapper_tee.c
+++ b/c/mapping/mapper_tee.c
@@ -16,7 +16,8 @@ typedef struct _mapper_tee_state_t {
 #define DEFAULT_COUNTER_FIELD_NAME "n"
 
 static void      mapper_tee_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_tee_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_tee_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_tee_alloc(int do_append, int flush_every_record,
 	char* output_file_name, cli_writer_opts_t* pwriter_opts);
 static void      mapper_tee_free(mapper_t* pmapper);
@@ -30,7 +31,9 @@ mapper_setup_t mapper_tee_setup = {
 };
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_tee_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_tee_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	int   do_append = FALSE;
 	int   flush_every_record = TRUE;
 	cli_writer_opts_t* pwriter_opts = mlr_malloc_or_die(sizeof(cli_writer_opts_t));
diff --git a/c/mapping/mapper_top.c b/c/mapping/mapper_top.c
index b689d90a4..db838ea61 100644
--- a/c/mapping/mapper_top.c
+++ b/c/mapping/mapper_top.c
@@ -28,7 +28,8 @@ typedef struct _mapper_top_state_t {
 } mapper_top_state_t;
 
 static void      mapper_top_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_top_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_top_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_top_alloc(ap_state_t* pargp, slls_t* pvalue_field_names, slls_t* pgroup_by_field_names,
 	int top_count, int do_max, int show_full_records, int allow_int_float);
 static void      mapper_top_free(mapper_t* pmapper);
@@ -59,7 +60,9 @@ static void mapper_top_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "optionally by category.\n");
 }
 
-static mapper_t* mapper_top_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_top_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	int     top_count             = 1;
 	slls_t* pvalue_field_names    = NULL;
 	slls_t* pgroup_by_field_names = slls_alloc();
diff --git a/c/mapping/mapper_uniq.c b/c/mapping/mapper_uniq.c
index b77d3e39f..857d31da1 100644
--- a/c/mapping/mapper_uniq.c
+++ b/c/mapping/mapper_uniq.c
@@ -19,9 +19,11 @@ typedef struct _mapper_uniq_state_t {
 } mapper_uniq_state_t;
 
 static void      mapper_uniq_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_uniq_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_uniq_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static void      mapper_count_distinct_usage(FILE* o, char* argv0, char* verb);
-static mapper_t* mapper_count_distinct_parse_cli(int* pargi, int argc, char** argv);
+static mapper_t* mapper_count_distinct_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __);
 static mapper_t* mapper_uniq_alloc(ap_state_t* pargp, slls_t* pgroup_by_field_names,
 	int show_counts, int show_num_distinct_only);
 static void      mapper_uniq_free(mapper_t* pmapper);
@@ -53,7 +55,9 @@ static void mapper_count_distinct_usage(FILE* o, char* argv0, char* verb) {
 }
 
 // ----------------------------------------------------------------
-static mapper_t* mapper_count_distinct_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_count_distinct_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	slls_t* pfield_names = NULL;
 	int     show_num_distinct_only = FALSE;
 
@@ -86,7 +90,9 @@ static void mapper_uniq_usage(FILE* o, char* argv0, char* verb) {
 	fprintf(o, "count-distinct. For uniq, -f is a synonym for -g.\n");
 }
 
-static mapper_t* mapper_uniq_parse_cli(int* pargi, int argc, char** argv) {
+static mapper_t* mapper_uniq_parse_cli(int* pargi, int argc, char** argv,
+	cli_reader_opts_t* _, cli_writer_opts_t* __)
+{
 	slls_t* pgroup_by_field_names = NULL;
 	int     show_counts = FALSE;
 	int     show_num_distinct_only = FALSE;
diff --git a/c/mlrmain.c b/c/mlrmain.c
index ec37b86af..3d91c8147 100644
--- a/c/mlrmain.c
+++ b/c/mlrmain.c
@@ -2,9 +2,9 @@
 #include <stdlib.h>
 #include <string.h>
 
-#include "cli/mlrcli.h"
 #include "lib/mlrutil.h"
 #include "lib/mlr_globals.h"
+#include "cli/mlrcli.h"
 #include "containers/lrec.h"
 #include "containers/sllv.h"
 #include "input/lrec_readers.h"
diff --git a/c/todo.txt b/c/todo.txt
index 9a21f2187..39f05d8f8 100644
--- a/c/todo.txt
+++ b/c/todo.txt
@@ -17,11 +17,13 @@ TOP OF LIST:
 ----------------------------------------------------------------
 4.5.0 for sure:
 
-* put/tee --oxxx flags overlays
+! rid entirely of MLR_GLOBALS.popts; all on the stack w/ population-order caveat.
+* mlh/mld for put/tee --oxxx flags overlays
 
 * xxxes
 * valgrinds
 
+k put/tee --oxxx flags overlays
 k mlrcli functionize
 k simplify mapper_join
 k -i, -o, --io