Make editor usable as a filter: echo foo | vis - | cat

The terminal output is by default redirected to stderr,
making stdout available for communications purposes.

If a file is "opened" from stdin (i.e. vis is given '-' as
argument) and a subsequent write without a filename is performed
as in ":wq" the output is written to stdout.

4 files changed, 53 insertions, 13 deletions

diff --git a/config.def.h b/config.def.h
index 9ecb018..9cd686a 100644
--- a/config.def.h
+++ b/config.def.h
@@ -1,5 +1,5 @@
 /** start by reading from the top of vis.c up until config.h is included */
-
+#define DEFAULT_TERM "xterm" /* default term to use if $TERM isn't set */
 /* macros used to specify keys for key bindings */
 #define ESC        0x1B
 #define NONE(k)    { .str = { k }, .code = 0 }
diff --git a/text.c b/text.c
index 7757e70..235c98c 100644
--- a/text.c
+++ b/text.c
@@ -645,12 +645,36 @@ err:
 	return -1;
 }
 
+ssize_t text_write(Text *txt, int fd) {
+	ssize_t len = 0;
+	text_iterate(txt, it, 0) {
+		size_t plen = it.end - it.start, poff = 0;
+		while (plen > 0) {
+			ssize_t res = write(fd, it.start + poff, plen);
+			if (res < 0) {
+				if (errno == EAGAIN || errno == EINTR)
+					continue;
+				return -1;
+			}
+			if (res == 0)
+				break;
+			poff += res;
+			plen -= res;
+		}
+		len += plen;
+	}
+	txt->saved_action = txt->undo;
+	text_snapshot(txt);
+	return len;
+}
+
 /* load the given file as starting point for further editing operations.
  * to start with an empty document, pass NULL as filename. */
 Text *text_load(const char *filename) {
 	Text *txt = calloc(1, sizeof(Text));
 	if (!txt)
 		return NULL;
+	txt->fd = -1;
 	txt->begin.index = 1;
 	txt->end.index = 2;
 	txt->piece_count = 2;
@@ -686,8 +710,10 @@ Text *text_load(const char *filename) {
 	}
 	return txt;
 out:
-	if (txt->fd > 2)
+	if (txt->fd > 2) {
 		close(txt->fd);
+		txt->fd = -1;
+	}
 	text_free(txt);
 	return NULL;
 }
@@ -1124,6 +1150,10 @@ void text_mark_clear_all(Text *txt) {
 		text_mark_clear(txt, mark);
 }
 
+int text_fd_get(Text *txt) {
+	return txt->fd;
+}
+
 const char *text_filename_get(Text *txt) {
 	return txt->filename;
 }
diff --git a/text.h b/text.h
index 34e350d..44c9f69 100644
--- a/text.h
+++ b/text.h
@@ -2,7 +2,7 @@
 #define TEXT_H
 
 #include <stdbool.h>
-#include <stddef.h>
+#include <sys/types.h>
 
 #define EPOS ((size_t)-1)         /* invalid position */
 
@@ -34,6 +34,9 @@ typedef struct {
 
 Text *text_load(const char *file);
 Text *text_load_fd(int fd);
+/* return the fd from which this text was loaded or -1 if it was
+ * loaded from a filename */
+int text_fd_get(Text*);
 /* the filename from which this text was loaded or first saved to */
 const char *text_filename_get(Text*);
 /* associate a filename with the yet unnamed buffer */
@@ -82,6 +85,7 @@ bool text_modified(Text*);
 /* test whether the underlying file uses UNIX style \n or Windows style \r\n newlines */
 bool text_newlines_crnl(Text*);
 int text_save(Text*, const char *file);
+ssize_t text_write(Text*, int fd);
 void text_free(Text*);
 
 typedef struct Regex Regex;
diff --git a/vis.c b/vis.c
index 9054ccc..554b4f7 100644
--- a/vis.c
+++ b/vis.c
@@ -1416,6 +1416,8 @@ static bool cmd_write(const char *argv[]) {
 	if (!argv[1])
 		argv[1] = text_filename_get(text);
 	if (!argv[1]) {
+		if (text_fd_get(text) == STDIN_FILENO)
+			return text_write(text, STDOUT_FILENO) >= 0;
 		editor_info_show(vis, "Filename expected");
 		return false;
 	}
@@ -1490,6 +1492,15 @@ static struct Screen {
 	bool need_resize;
 } screen = { .need_resize = true };
 
+static void die(const char *errstr, ...) {
+	va_list ap;
+	endwin();
+	va_start(ap, errstr);
+	vfprintf(stderr, errstr, ap);
+	va_end(ap);
+	exit(EXIT_FAILURE);
+}
+
 static void sigwinch_handler(int sig) {
 	screen.need_resize = true;
 }
@@ -1513,7 +1524,11 @@ static void setup() {
 	setlocale(LC_CTYPE, "");
 	if (!getenv("ESCDELAY"))
 		set_escdelay(50);
-	initscr();
+	char *term = getenv("TERM");
+	if (!term)
+		term = DEFAULT_TERM;
+	if (!newterm(term, stderr, stdin) == ERR)
+		die("Can not initialize terminal\n");
 	start_color();
 	raw();
 	noecho();
@@ -1574,15 +1589,6 @@ static Key getkey(void) {
 	return key;
 }
 
-static void die(const char *errstr, ...) {
-	va_list ap;
-	endwin();
-	va_start(ap, errstr);
-	vfprintf(stderr, errstr, ap);
-	va_end(ap);
-	exit(EXIT_FAILURE);
-}
-
 static void mainloop() {
 	struct timeval idle = { .tv_usec = 0 }, *timeout = NULL;
 	Key key, key_prev, *key_mod = NULL;