[st][PATCH] externalpipe and externalpipein

This patch must be applied on the externalpipe patch. It adds the
function externalpipein to redirect the standard output of the external
command to the slave size of the pty, that is, as if the external
program had been manually executed on the terminal. It can be used to
send desired escape sequences to the terminal with a shortcut.

I created the patch to make use of the dynamic-colors program
(https://github.com/sos4nt/dynamic-colors) that uses the OSC escape
sequences to change the colors of the terminal. The program keeps the
last colorscheme selected in a file, so you can use it to select the
colorscheme for all newly opened terminals from that moment on. If you
want to change the color of the background and foreground independently
from the palette, you have to merge in the patch for the OSC escape
sequences 10, 11, and 12.

This patch includes the changes of the externalpipe sigaction patch to
prevent reseting the signal handler for SIGCHLD when the proces of the
external command exits.

README.md

@@ -15,7 +15,7 @@ Refer to [https://st.suckless.org/](https://st.suckless.org/) for details on the
 
 ### Changelog:
 
-2020-04-20 - Added the force redraw on pselect after key is pressed patch and the externalpipe sigaction patch
+2020-04-20 - Upgrade to c279f5, 2020-04-19, and added the force redraw on pselect after key is pressed patch and the externalpipein patch
 
 2020-03-29 - Added invert and workingdir patches
 
@@ -60,8 +60,10 @@ Refer to [https://st.suckless.org/](https://st.suckless.org/) for details on the
    - [externalpipe](https://st.suckless.org/patches/externalpipe/)
       - this patch allows for eading and writing st's screen through a pipe, e.g. to pass info to dmenu
 
-   - [externalpipe-sigaction](https://lists.suckless.org/hackers/2004/17216.html)
+   - [externalpipein](https://lists.suckless.org/hackers/2004/17218.html)
       - this patch prevents the reset of the signal handler set on SIGCHILD, when the forked process that executes the external process exits
+      - it adds the externalpipein function to redirect the standard output of the external command to the slave size of the pty, that is, as if the external program had been manually executed on the terminal
+      - this can be used to send desired escape sequences to the terminal with a shortcut (e.g. to change colors)
 
    - [~fixime~](https://st.suckless.org/patches/fix_ime/)
       - adds better Input Method Editor (IME) support

patch/externalpipe.c

@@ -1,5 +1,9 @@
 void
+#if EXTERNALPIPEIN_PATCH
+extpipe(const Arg *arg, int in)
+#else
 externalpipe(const Arg *arg)
+#endif // EXTERNALPIPEIN_PATCH
 {
 	int to[2];
 	char buf[UTF_SIZ];
@@ -19,6 +23,11 @@ externalpipe(const Arg *arg)
 		dup2(to[0], STDIN_FILENO);
 		close(to[0]);
 		close(to[1]);
+		#if EXTERNALPIPEIN_PATCH
+		if (in)
+			dup2(csdfd, STDOUT_FILENO);
+		close(csdfd);
+		#endif // EXTERNALPIPEIN_PATCH
 		execvp(((char **)arg->v)[0], (char **)arg->v);
 		fprintf(stderr, "st: execvp %s\n", ((char **)arg->v)[0]);
 		perror("failed");
@@ -50,3 +59,15 @@ externalpipe(const Arg *arg)
 	/* restore */
 	signal(SIGPIPE, oldsigpipe);
 }
+
+#if EXTERNALPIPEIN_PATCH
+void
+externalpipe(const Arg *arg) {
+	extpipe(arg, 0);
+}
+
+void
+externalpipein(const Arg *arg) {
+	extpipe(arg, 1);
+}
+#endif // EXTERNALPIPEIN_PATCH

patch/externalpipe.h

@@ -1 +1,4 @@
 void externalpipe(const Arg *);
+#if EXTERNALPIPEIN_PATCH
+void externalpipein(const Arg *);
+#endif // EXTERNALPIPEIN_PATCH

patches.def.h

@@ -68,12 +68,23 @@
  */
 #define EXTERNALPIPE_PATCH 0
 
-/* This patch prevents the reset of the signal handler set on SIGCHILD, when
+/* This patch improves and extends the externalpipe patch in two ways:
- * the forked process that executes the external process exits.
+ *    - it prevents the reset of the signal handler set on SIGCHILD, when
+ *      the forked process that executes the external process exits and
+ *    - it adds the externalpipein function to redirect the standard output
+ *      of the external command to the slave size of the pty, that is, as if
+ *      the external program had been manually executed on the terminal
+ *
+ * It can be used to send desired escape sequences to the terminal with a
+ * keyboard shortcut. The patch was created to make use of the dynamic-colors
+ * tool that uses the OSC escape sequences to change the colors of the terminal.
+ *
  * This patch depends on EXTERNALPIPE_PATCH being enabled.
- * https://lists.suckless.org/hackers/2004/17216.html
+ *
+ * https://github.com/sos4nt/dynamic-colors
+ * https://lists.suckless.org/hackers/2004/17218.html
  */
-#define EXTERNALPIPE_SIGACTION_PATCH 0
+#define EXTERNALPIPEIN_PATCH 0
 
 /* This patch allows command line applications to use all the fancy key combinations
  * that are available to GUI applications.

st.c

@@ -245,6 +245,9 @@ static CSIEscape csiescseq;
 static STREscape strescseq;
 static int iofd = 1;
 static int cmdfd;
+#if EXTERNALPIPEIN_PATCH && EXTERNALPIPE_PATCH
+static int csdfd;
+#endif // EXTERNALPIPEIN_PATCH
 static pid_t pid;
 
 static uchar utfbyte[UTF_SIZ + 1] = {0x80,    0, 0xC0, 0xE0, 0xF0};
@@ -782,16 +785,20 @@ sigchld(int a)
 	int stat;
 	pid_t p;
 
-	#if EXTERNALPIPE_SIGACTION_PATCH && EXTERNALPIPE_PATCH
+	#if EXTERNALPIPEIN_PATCH && EXTERNALPIPE_PATCH
 	if ((p = waitpid(-1, &stat, WNOHANG)) < 0)
 	#else
 	if ((p = waitpid(pid, &stat, WNOHANG)) < 0)
-	#endif // EXTERNALPIPE_SIGACTION_PATCH
+	#endif // EXTERNALPIPEIN_PATCH
 		die("waiting for pid %hd failed: %s\n", pid, strerror(errno));
 
 	if (pid != p)
 		return;
 
+	#if EXTERNALPIPEIN_PATCH && EXTERNALPIPE_PATCH
+	close(csdfd);
+	#endif // EXTERNALPIPEIN_PATCH
+
 	if (WIFEXITED(stat) && WEXITSTATUS(stat))
 		die("child exited with status %d\n", WEXITSTATUS(stat));
 	else if (WIFSIGNALED(stat))
@@ -827,9 +834,9 @@ int
 ttynew(char *line, char *cmd, char *out, char **args)
 {
 	int m, s;
-	#if EXTERNALPIPE_SIGACTION_PATCH && EXTERNALPIPE_PATCH
+	#if EXTERNALPIPEIN_PATCH && EXTERNALPIPE_PATCH
 	struct sigaction sa;
-	#endif // EXTERNALPIPE_SIGACTION_PATCH
+	#endif // EXTERNALPIPEIN_PATCH
 
 	if (out) {
 		term.mode |= MODE_PRINT;
@@ -885,14 +892,15 @@ ttynew(char *line, char *cmd, char *out, char **args)
 #endif
 		close(s);
 		cmdfd = m;
-		#if EXTERNALPIPE_SIGACTION_PATCH && EXTERNALPIPE_PATCH
+		#if EXTERNALPIPEIN_PATCH && EXTERNALPIPE_PATCH
+		csdfd = s;
 		memset(&sa, 0, sizeof(sa));
 		sigemptyset(&sa.sa_mask);
 		sa.sa_handler = sigchld;
 		sigaction(SIGCHLD, &sa, NULL);
 		#else
 		signal(SIGCHLD, sigchld);
-		#endif // EXTERNALPIPE_SIGACTION_PATCH
+		#endif // EXTERNALPIPEIN_PATCH
 		break;
 	}
 	return cmdfd;