Add JQ_COLORS env var for color config (fix #1252)

src/jq.h

@@ -66,4 +66,6 @@ jv jq_util_input_get_position(jq_state*);
 jv jq_util_input_get_current_filename(jq_state*);
 jv jq_util_input_get_current_line(jq_state*);
 
+int jq_set_colors(const char *);
+
 #endif /* !JQ_H */

src/jv_print.c

@@ -27,11 +27,46 @@
 static const jv_kind color_kinds[] =
   {JV_KIND_NULL,   JV_KIND_FALSE, JV_KIND_TRUE, JV_KIND_NUMBER,
    JV_KIND_STRING, JV_KIND_ARRAY, JV_KIND_OBJECT};
-static const char* const colors[] =
+static char color_bufs[sizeof(color_kinds)/sizeof(color_kinds[0])][16];
+static const char *color_bufps[8];
+static const char* def_colors[] =
   {COL("1;30"),    COL("0;39"),      COL("0;39"),     COL("0;39"),
    COL("0;32"),      COL("1;39"),     COL("1;39")};
 #define FIELD_COLOR COL("34;1")
 
+static const char **colors = def_colors;
+
+int
+jq_set_colors(const char *c)
+{
+  const char *e;
+  size_t i;
+
+  if (c == NULL)
+    return 1;
+  colors = def_colors;
+  memset(color_bufs, 0, sizeof(color_bufs));
+  for (i = 0; i < sizeof(def_colors) / sizeof(def_colors[0]); i++)
+    color_bufps[i] = def_colors[i];
+  for (i = 0; i < sizeof(def_colors) / sizeof(def_colors[0]) && *c != '\0'; i++, c = e) {
+    if ((e = strchr(c, ':')) == NULL)
+      e = c + strlen(c);
+    if ((size_t)(e - c) > sizeof(color_bufs[i]) - 4 /* ESC [ m NUL */)
+      return 0;
+    color_bufs[i][0] = ESC[0];
+    color_bufs[i][1] = '[';
+    (void) strncpy(&color_bufs[i][2], c, e - c);
+    if (strspn(&color_bufs[i][2], "0123456789;") < strlen(&color_bufs[i][2]))
+      return 0;
+    color_bufs[i][2 + (e - c)] = 'm';
+    color_bufps[i] = color_bufs[i];
+    if (e[0] == ':')
+      e++;
+  }
+  colors = color_bufps;
+  return 1;
+}
+
 static void put_buf(const char *s, int len, FILE *fout, jv *strout, int is_tty) {
   if (strout) {
     *strout = jv_string_append_buf(*strout, s, len);

src/main.c

@@ -525,6 +525,9 @@ int main(int argc, char* argv[]) {
   if (options & COLOR_OUTPUT) dumpopts |= JV_PRINT_COLOR;
   if (options & NO_COLOR_OUTPUT) dumpopts &= ~JV_PRINT_COLOR;
 
+  if (getenv("JQ_COLORS") != NULL && !jq_set_colors(getenv("JQ_COLORS")))
+      fprintf(stderr, "Failed to set $JQ_COLORS\n");
+
   if (jv_get_kind(lib_search_paths) == JV_KIND_NULL) {
     // Default search path list
     lib_search_paths = JV_ARRAY(jv_string("~/.jq"),