From: WanBingjiang <wanbingjiang@webray.com.cn>
Date: Thu, 5 Feb 2026 09:02:39 +0000 (+0800)
Subject: libsmartcols: support JSON Lines format output
X-Git-Tag: v2.43-devel~50^2~6
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=08f4133918df90caa4ee4ebd118a8696a7849833;p=thirdparty%2Futil-linux.git

libsmartcols: support JSON Lines format output
---

diff --git a/include/jsonwrt.h b/include/jsonwrt.h
index 31e180abe..74b43e213 100644
--- a/include/jsonwrt.h
+++ b/include/jsonwrt.h
@@ -11,14 +11,21 @@ enum {
 	UL_JSON_VALUE
 };
 
+typedef enum {
+	UL_JSON_PRETTY,
+	UL_JSON_COMPACT,
+	UL_JSON_LINE,
+} ul_json_format_t;
+
 struct ul_jsonwrt {
 	FILE *out;
 	int indent;
 
 	unsigned int after_close :1;
+	ul_json_format_t json_format;
 };
 
-void ul_jsonwrt_init(struct ul_jsonwrt *fmt, FILE *out, int indent);
+void ul_jsonwrt_init(struct ul_jsonwrt *fmt, FILE *out, int indent, ul_json_format_t json_format);
 int ul_jsonwrt_is_ready(struct ul_jsonwrt *fmt);
 void ul_jsonwrt_indent(struct ul_jsonwrt *fmt);
 void ul_jsonwrt_open(struct ul_jsonwrt *fmt, const char *name, int type);
diff --git a/lib/jsonwrt.c b/lib/jsonwrt.c
index 365d845ce..692592975 100644
--- a/lib/jsonwrt.c
+++ b/lib/jsonwrt.c
@@ -102,10 +102,11 @@ static void fputs_quoted_case_json(const char *data, FILE *out, int dir, size_t
 #define fputs_quoted_json_upper(_d, _o) fputs_quoted_case_json(_d, _o, 1, 0)
 #define fputs_quoted_json_lower(_d, _o) fputs_quoted_case_json(_d, _o, -1, 0)
 
-void ul_jsonwrt_init(struct ul_jsonwrt *fmt, FILE *out, int indent)
+void ul_jsonwrt_init(struct ul_jsonwrt *fmt, FILE *out, int indent, ul_json_format_t json_format)
 {
 	fmt->out = out;
 	fmt->indent = indent;
+	fmt->json_format = json_format;
 	fmt->after_close = 0;
 }
 
@@ -124,81 +125,92 @@ void ul_jsonwrt_indent(struct ul_jsonwrt *fmt)
 
 static void print_name(struct ul_jsonwrt *fmt, const char *name)
 {
-	if (name) {
-		if (fmt->after_close)
-			fputs(",\n", fmt->out);
-		ul_jsonwrt_indent(fmt);
-		fputs_quoted_json_lower(name, fmt->out);
-	} else {
-		if (fmt->after_close)
-			fputs(",", fmt->out);
+	if (fmt->after_close) {
+		if (fmt->json_format == UL_JSON_LINE)
+			fputs(fmt->indent == 0 ? "\n" : ",", fmt->out);
 		else
-			ul_jsonwrt_indent(fmt);
+			fputs(name ? ",\n" : ",", fmt->out);
 	}
+	if (fmt->json_format != UL_JSON_LINE && (name || !fmt->after_close))
+		ul_jsonwrt_indent(fmt);
+	if (name)
+		fputs_quoted_json_lower(name, fmt->out);
 }
 
 void ul_jsonwrt_open(struct ul_jsonwrt *fmt, const char *name, int type)
 {
+	const char *s = "";
+
 	print_name(fmt, name);
 
 	switch (type) {
 	case UL_JSON_OBJECT:
-		fputs(name ? ": {\n" : "{\n", fmt->out);
+		s = fmt->json_format == UL_JSON_LINE ? (name ? ":{" : "{") : (name ? ": {\n" : "{\n");
 		fmt->indent++;
 		break;
 	case UL_JSON_ARRAY:
-		fputs(name ? ": [\n" : "[\n", fmt->out);
+		s = fmt->json_format == UL_JSON_LINE ? (name ? ":[" : "[") : (name ? ": [\n" : "[\n");
 		fmt->indent++;
 		break;
 	case UL_JSON_VALUE:
-		fputs(name ? ": " : " ", fmt->out);
+		s = fmt->json_format == UL_JSON_LINE ? (name ? ":" : "") : (name ? ": " : " ");
 		break;
 	}
+	fputs(s, fmt->out);
 	fmt->after_close = 0;
 }
 
 void ul_jsonwrt_empty(struct ul_jsonwrt *fmt, const char *name, int type)
 {
+	const char *s = "";
+
 	print_name(fmt, name);
 
 	switch (type) {
 	case UL_JSON_OBJECT:
-		fputs(name ? ": {}" : "{}", fmt->out);
+		s = fmt->json_format == UL_JSON_LINE ? (name ? ":{}" : "{}") : (name ? ": {}" : "{}");
 		break;
 	case UL_JSON_ARRAY:
-		fputs(name ? ": []" : "[]", fmt->out);
+		s = fmt->json_format == UL_JSON_LINE ? (name ? ":[]" : "[]") : (name ? ": []" : "[]");
 		break;
 	case UL_JSON_VALUE:
-		fputs(name ? ": null" : "null", fmt->out);
+		s = fmt->json_format == UL_JSON_LINE ? (name ? ":null" : "null") : (name ? ": null" : "null");
 		break;
 	}
-
+	fputs(s, fmt->out);
 	fmt->after_close = 1;
 }
 
 void ul_jsonwrt_close(struct ul_jsonwrt *fmt, int type)
 {
+	char endchr;
+
 	assert(fmt->indent > 0);
 
 	switch (type) {
 	case UL_JSON_OBJECT:
 		fmt->indent--;
-		fputc('\n', fmt->out);
-		ul_jsonwrt_indent(fmt);
-		fputs("}", fmt->out);
-		if (fmt->indent == 0)
-			fputs("\n", fmt->out);
+		endchr = '}';
 		break;
 	case UL_JSON_ARRAY:
 		fmt->indent--;
-		fputc('\n', fmt->out);
-		ul_jsonwrt_indent(fmt);
-		fputs("]", fmt->out);
+		endchr = ']';
 		break;
 	case UL_JSON_VALUE:
-		break;
+		fmt->after_close = 1;
+		return;
+	default:
+		fmt->after_close = 1;
+		return;
 	}
 
+	if (fmt->json_format != UL_JSON_LINE) {
+		fputc('\n', fmt->out);
+		ul_jsonwrt_indent(fmt);
+	}
+	fputc(endchr, fmt->out);
+	if (fmt->json_format != UL_JSON_LINE && type == UL_JSON_OBJECT && fmt->indent == 0)
+		fputc('\n', fmt->out);
 	fmt->after_close = 1;
 }
 
diff --git a/libfdisk/src/script.c b/libfdisk/src/script.c
index 62ca5eeb2..c7164fe0d 100644
--- a/libfdisk/src/script.c
+++ b/libfdisk/src/script.c
@@ -562,7 +562,7 @@ static int write_file_json(struct fdisk_script *dp, FILE *f)
 
 	DBG(SCRIPT, ul_debugobj(dp, "writing json dump to file"));
 
-	ul_jsonwrt_init(&json, f, 0);
+	ul_jsonwrt_init(&json, f, 0, UL_JSON_PRETTY);
 	ul_jsonwrt_root_open(&json);
 
 	ul_jsonwrt_object_open(&json, "partitiontable");
diff --git a/libsmartcols/src/filter.c b/libsmartcols/src/filter.c
index 4923cd802..70bc57cdc 100644
--- a/libsmartcols/src/filter.c
+++ b/libsmartcols/src/filter.c
@@ -229,7 +229,7 @@ int scols_dump_filter(struct libscols_filter *fltr, FILE *out)
 	if (!fltr || !out)
 		return -EINVAL;
 
-	ul_jsonwrt_init(&json, out, 0);
+	ul_jsonwrt_init(&json, out, 0, UL_JSON_PRETTY);
 	ul_jsonwrt_root_open(&json);
 
 	filter_dump_node(&json, fltr->root);
diff --git a/libsmartcols/src/print-api.c b/libsmartcols/src/print-api.c
index 52b266435..15841b2bc 100644
--- a/libsmartcols/src/print-api.c
+++ b/libsmartcols/src/print-api.c
@@ -117,11 +117,13 @@ static int do_print_table(struct libscols_table *tb, int *is_empty)
 	if (list_empty(&tb->tb_lines)) {
 		DBG(TAB, ul_debugobj(tb, "ignore -- no lines"));
 		if (scols_table_is_json(tb)) {
-			ul_jsonwrt_init(&tb->json, tb->out, 0);
-			ul_jsonwrt_root_open(&tb->json);
-			ul_jsonwrt_array_open(&tb->json, tb->name ? tb->name : "");
-			ul_jsonwrt_array_close(&tb->json);
-			ul_jsonwrt_root_close(&tb->json);
+			ul_jsonwrt_init(&tb->json, tb->out, 0, tb->json_format);
+			if (tb->json_format != UL_JSON_LINE) {
+				ul_jsonwrt_root_open(&tb->json);
+				ul_jsonwrt_array_open(&tb->json, tb->name ? tb->name : "");
+				ul_jsonwrt_array_close(&tb->json);
+				ul_jsonwrt_root_close(&tb->json);
+			}
 		} else if (is_empty)
 			*is_empty = 1;
 		return 0;
@@ -132,7 +134,7 @@ static int do_print_table(struct libscols_table *tb, int *is_empty)
 	if (rc)
 		return rc;
 
-	if (scols_table_is_json(tb)) {
+	if (scols_table_is_json(tb) && tb->json_format != UL_JSON_LINE) {
 		ul_jsonwrt_root_open(&tb->json);
 		ul_jsonwrt_array_open(&tb->json, tb->name ? tb->name : "");
 	}
@@ -150,8 +152,12 @@ static int do_print_table(struct libscols_table *tb, int *is_empty)
 		rc = __scols_print_table(tb, &buf);
 
 	if (scols_table_is_json(tb)) {
-		ul_jsonwrt_array_close(&tb->json);
-		ul_jsonwrt_root_close(&tb->json);
+		if (tb->json_format != UL_JSON_LINE) {
+			ul_jsonwrt_array_close(&tb->json);
+			ul_jsonwrt_root_close(&tb->json);
+		} else {
+			fputc('\n', tb->out);	/* trailing newline after last object */
+		}
 	}
 done:
 	__scols_cleanup_printing(tb, &buf);
diff --git a/libsmartcols/src/print.c b/libsmartcols/src/print.c
index c1b81c50f..488bb86d6 100644
--- a/libsmartcols/src/print.c
+++ b/libsmartcols/src/print.c
@@ -1287,7 +1287,7 @@ int __scols_initialize_printing(struct libscols_table *tb, struct ul_buffer *buf
 		extra_bufsz += tb->ncols;			/* separator between columns */
 		break;
 	case SCOLS_FMT_JSON:
-		ul_jsonwrt_init(&tb->json, tb->out, 0);
+		ul_jsonwrt_init(&tb->json, tb->out, 0, tb->json_format);
 		extra_bufsz += tb->nlines * 3;		/* indentation */
 		FALLTHROUGH;
 	case SCOLS_FMT_EXPORT:
diff --git a/libsmartcols/src/smartcolsP.h b/libsmartcols/src/smartcolsP.h
index 1e9dcec01..07df40d8a 100644
--- a/libsmartcols/src/smartcolsP.h
+++ b/libsmartcols/src/smartcolsP.h
@@ -270,6 +270,8 @@ struct libscols_table {
 	struct libscols_line *cur_line;		/* currently used line */
 	struct libscols_column *cur_column;	/* currently used column */
 
+	ul_json_format_t json_format;	/* JSON output format */
+
 	/* flags */
 	bool		ascii	      ,	/* don't use unicode */
 			colors_wanted ,	/* enable colors */
diff --git a/libsmartcols/src/table.c b/libsmartcols/src/table.c
index aa7cdf3c6..13360ce93 100644
--- a/libsmartcols/src/table.c
+++ b/libsmartcols/src/table.c
@@ -60,6 +60,22 @@ static void check_padding_debug(struct libscols_table *tb)
 	tb->padding_debug = 1;
 }
 
+static ul_json_format_t get_json_format(void)
+{
+	const char *str;
+
+	str = getenv("LIBSMARTCOLS_JSON");
+	if (!str)
+		return UL_JSON_PRETTY;
+	else if (strcmp(str, "compact") == 0)
+		return UL_JSON_COMPACT;
+	else if (strcmp(str, "lines") == 0)
+		return UL_JSON_LINE;
+
+	/* default to pretty */
+	return UL_JSON_PRETTY;
+}
+
 /**
  * scols_new_table:
  *
@@ -87,6 +103,7 @@ struct libscols_table *scols_new_table(void)
 
 	DBG(TAB, ul_debugobj(tb, "alloc"));
 	ON_DBG(INIT, check_padding_debug(tb));
+	tb->json_format = get_json_format();
 
 	return tb;
 }
diff --git a/sys-utils/dmesg.c b/sys-utils/dmesg.c
index 854786554..fd1dd0cfb 100644
--- a/sys-utils/dmesg.c
+++ b/sys-utils/dmesg.c
@@ -1145,7 +1145,7 @@ static void print_record(struct dmesg_control *ctl,
 
 	if (ctl->json) {
 		if (!ul_jsonwrt_is_ready(&ctl->jfmt)) {
-			ul_jsonwrt_init(&ctl->jfmt, stdout, 0);
+			ul_jsonwrt_init(&ctl->jfmt, stdout, 0, UL_JSON_PRETTY);
 			ul_jsonwrt_root_open(&ctl->jfmt);
 			ul_jsonwrt_array_open(&ctl->jfmt, "dmesg");
 		}