From 2d6e7b611e8d77e4db5b8fa7b619a2574537a30a Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20Ankarstr=C3=B6m?= <john@ankarstrom.se>
Date: Mon, 7 Jun 2021 23:53:25 +0200
Subject: Add explanatory comments

---
 tterm.c | 91 +++++++++++++++++++++++++++++++++++++----------------------------
 1 file changed, 52 insertions(+), 39 deletions(-)

diff --git a/tterm.c b/tterm.c
index 648fa5c..3a71821 100644
--- a/tterm.c
+++ b/tterm.c
@@ -20,13 +20,13 @@ Display *display;
 
 #define die(...) do{fprintf(stderr,__VA_ARGS__);exit(1);}while(0)
 
-unsigned char *pidprop = 0;
-
+/* find window associated with pid */
 Window
 findwindow(unsigned int pid, Window w)
 {
 	Atom type;
 	int format;
+	unsigned char *pidprop;
 	unsigned int i, nchildren;
 	unsigned long nitems, bytes_after;
 	Window *children, _root, parent;
@@ -45,18 +45,21 @@ findwindow(unsigned int pid, Window w)
 	return 0;
 }
 
+/* copy cwd and rewrite /home/ */
 char *
-wd(char *path)
+cwdcpy(char *path)
 {
-	char *username, *r;
+	char *user, *r;
+	int len;
 
-	username = getenv("USER");
 	r = strdup(path);
 
-        if (strncmp(r, "/home/", 6) == 0) {
-                r += 5;
-                if (strncmp(r + 1, username, strlen(username)) == 0)
-                        r += strlen(username);
+        if (strncmp(path, "/home/", sizeof("/home")-1) == 0) {
+		user = getenv("USER");
+		len = strlen(user);
+                r += sizeof("/home")-1;
+                if (strncmp(r + 1, user, len) == 0)
+                        r += len;
                 r[0] = '~';
         }
 
@@ -72,19 +75,28 @@ main(int argc, char *argv[])
 	pid_t child;
 	size_t size;
 	ssize_t len;
-	Window root, w;
-
-	/* create fifo */
+	Window w;
 
-	writefile = malloc(40*sizeof(char));
-	if (writefile == NULL) err(1, "malloc");
+	if ((display = XOpenDisplay(0)) == NULL)
+		die("could not open display\n");
 
-	sprintf(writefile, "/var/tmp/tterm/%d.w", getpid());
+	/* create fifo directory */
 	if (mkdir("/var/tmp/tterm", 0700) == -1 && errno != EEXIST)
 		err(1, "mkdir");
 
+	/* build fifo path */
+	if ((writefile = malloc(40*sizeof(char))) == NULL)
+		err(1, "malloc");
+	sprintf(writefile, "/var/tmp/tterm/%d.w", getpid());
+
+	/* create fifo */
 	unlink(writefile);
-	if (mkfifo(writefile, 0600) == -1) err(1, "mkfifo");
+	if (mkfifo(writefile, 0600) == -1)
+		err(1, "mkfifo");
+
+	/* retrieve atom for _NET_WM_PID */
+	pidatom = XInternAtom(display, "_NET_WM_PID", 1);
+	if (pidatom == None) die("no _NET_WM_PID atom found\n");
 
 	/* start terminal */
 	if ((child = fork()) == 0) {
@@ -92,35 +104,37 @@ main(int argc, char *argv[])
 		err(1, "execvp");
 	}
 
-	/* find new window */
+	/* find window belonging to child */
+	for (i = 0; !w && i < MAX_LOOK; i++)
+		w = findwindow(child, XDefaultRootWindow(display));
+	if (!w)
+		die("could not find window\n");
 
-	display = XOpenDisplay(0);
-	if (display == NULL) die("could not open display\n");
-
-	root = XDefaultRootWindow(display);
-	pidatom = XInternAtom(display, "_NET_WM_PID", 1);
-	if (pidatom == None) die("no _NET_WM_PID atom found\n");
-
-	for (i = 0; !w && i++ < MAX_LOOK; w = findwindow(child, root)) ;
-	if (!w) die("could not find window\n");
-
-	/* watch fifo and update title */
-	writefp = fopen(writefile, "r");
-	if (writefp == NULL) err(1, "fopen");
-
-	cmd = malloc(MAX_CMD*sizeof(char));
-	if (cmd == NULL) err(1, "malloc");
+	/* read from fifo */
+	if ((writefp = fopen(writefile, "r")) == NULL)
+		err(1, "fopen");
+	if ((cmd = malloc(MAX_CMD*sizeof(char))) == NULL)
+		err(1, "malloc");
 
 	line = NULL;
 	size = 0;
+
+	/* get first line and unlink fifo */
+	if ((len = getline(&line, &size, writefp)) == -1) goto end;
+	unlink(writefile);
+	goto loop;
+
+	/* process line and update title */
 	while ((len = getline(&line, &size, writefp)) != -1) {
-		if (strncmp(line, "cwd", 3) == 0) {
-			line += 3; line[len-4] = 0; /* chomp */
-			cwd = wd(line);
+loop:		if (strncmp(line, "cwd", 3) == 0) {
+			line[len-1] = 0;
+			line += 3;
+			cwd = cwdcpy(line);
 			XStoreName(display, w, cwd);
 			XFlush(display);
 		} else if (strncmp(line, "cmd", 3) == 0) {
-			line += 3; line[len-4] = 0; /* chomp */
+			line[len-1] = 0;
+			line += 3;
 			if (strncmp(line, "fg", 2) != 0)
 				snprintf(cmd, MAX_CMD, "%s (%s)", line, cwd);
 			XStoreName(display, w, cmd);
@@ -131,6 +145,5 @@ main(int argc, char *argv[])
 		}
 	}
 
-	unlink(writefile);
-	XCloseDisplay(display);
+end:	XCloseDisplay(display);
 }
-- 
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