Merge pull request beejjorgensen#2 from Azhrei/master

Updates to bring the Guide into the 21st century

bin/bg2fo

@@ -1,4 +1,4 @@
-#!/usr/bin/python2
+#!/usr/bin/env python2.7
 #
 # bg2fo -- convert bg to Formatting Object XML
 #

bin/bg2html

@@ -1,4 +1,4 @@
-#!/usr/bin/python2
+#!/usr/bin/env python2.7
 #
 # bg2conv -- a semi-hardcoded parser for Beej's Guide XML files
 #

examples/echoc.c

@@ -15,8 +15,11 @@
 
 int main(void)
 {
-    int s, t, len;
-    struct sockaddr_un remote;
+    int s, len;
+    struct sockaddr_un remote = {
+        .sun_family = AF_UNIX,
+        // .sun_path = SOCK_PATH,   // Can't do assignment to an array
+    };
     char str[100];
 
     if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
@@ -26,7 +29,6 @@ int main(void)
 
     printf("Trying to connect...\n");
 
-    remote.sun_family = AF_UNIX;
     strcpy(remote.sun_path, SOCK_PATH);
     len = strlen(remote.sun_path) + sizeof(remote.sun_family);
     if (connect(s, (struct sockaddr *)&remote, len) == -1) {
@@ -36,17 +38,18 @@ int main(void)
 
     printf("Connected.\n");
 
-    while(printf("> "), fgets(str, 100, stdin), !feof(stdin)) {
-        if (send(s, str, strlen(str), 0) == -1) {
+    /* size in fgets() includes the null byte */
+    while(printf("> "), fgets(str, sizeof(str), stdin), !feof(stdin)) {
+        if (send(s, str, strlen(str)+1, 0) == -1) {
             perror("send");
             exit(1);
         }
 
-        if ((t=recv(s, str, 100, 0)) > 0) {
-            str[t] = '\0';
+        if ((len=recv(s, str, sizeof(str)-1, 0)) > 0) {
+            str[len] = '\0';
             printf("echo> %s", str);
         } else {
-            if (t < 0) perror("recv");
+            if (len < 0) perror("recv");
             else printf("Server closed connection\n");
             exit(1);
         }
@@ -56,6 +59,3 @@ int main(void)
 
     return 0;
 }
-
-
-

examples/echos.c

@@ -16,16 +16,17 @@
 int main(void)
 {
 	int s, s2, len;
-	unsigned t;
-	struct sockaddr_un local, remote;
+	struct sockaddr_un remote, local = {
+            .sun_family = AF_UNIX,
+            // .sun_path = SOCK_PATH,   // Can't do assignment to an array
+        };
 	char str[100];
 
 	if ((s = socket(AF_UNIX, SOCK_STREAM, 0)) == -1) {
 		perror("socket");
 		exit(1);
 	}
 
-	local.sun_family = AF_UNIX;
 	strcpy(local.sun_path, SOCK_PATH);
 	unlink(local.sun_path);
 	len = strlen(local.sun_path) + sizeof(local.sun_family);
@@ -42,8 +43,8 @@ int main(void)
 	for(;;) {
 		int done, n;
 		printf("Waiting for a connection...\n");
-		t = sizeof(remote);
-		if ((s2 = accept(s, (struct sockaddr *)&remote, &t)) == -1) {
+		socklen_t slen = sizeof(remote);
+		if ((s2 = accept(s, (struct sockaddr *)&remote, &slen)) == -1) {
 			perror("accept");
 			exit(1);
 		}
@@ -52,7 +53,7 @@ int main(void)
 
 		done = 0;
 		do {
-			n = recv(s2, str, 100, 0);
+			n = recv(s2, str, sizeof(str), 0);
 			if (n <= 0) {
 				if (n < 0) perror("recv");
 				done = 1;
@@ -70,6 +71,3 @@ int main(void)
 
 	return 0;
 }
-
-
-

examples/fork1.c

@@ -14,6 +14,8 @@ int main(void)
 	pid_t pid;
 	int rv;
 
+        // Be sure to flush all stdio buffers, or the output will be
+        // duplicated when both parent and child flush them later!
 	switch(pid = fork()) {
 	case -1:
 		perror("fork");  /* something went wrong */
@@ -40,4 +42,3 @@ int main(void)
 
 	return 0;
 }
-

examples/kirk.c

@@ -41,7 +41,7 @@ int main(void)
 		/* ditch newline at end, if it exists */
 		if (buf.mtext[len-1] == '\n') buf.mtext[len-1] = '\0';
 
-		if (msgsnd(msqid, &buf, len+1, 0) == -1) /* +1 for '\0' */
+		if (msgsnd(msqid, &buf, len, 0) == -1)
 			perror("msgsnd");
 	}
 
@@ -52,4 +52,3 @@ int main(void)
 
 	return 0;
 }
-

examples/lockdemo.c

@@ -10,14 +10,16 @@
 
 int main(int argc, char *argv[])
 {
-	                /* l_type   l_whence  l_start  l_len  l_pid   */
-	struct flock fl = {F_WRLCK, SEEK_SET,   0,      0,     0 };
+	struct flock fl = {
+            .l_type = F_WRLCK,
+            .l_whence = SEEK_SET,
+            .l_start = 0,
+            .l_len = 0,
+        };
 	int fd;
 
 	(void)argv; // silence unused warning
 
-	fl.l_pid = getpid();
-
 	if (argc > 1) 
 		fl.l_type = F_RDLCK;
 
@@ -52,4 +54,3 @@ int main(int argc, char *argv[])
 
 	return 0;
 }
-

examples/mmapdemo.c

@@ -14,7 +14,7 @@
 int main(int argc, char *argv[])
 {
 	int fd, offset;
-	char *data;
+	void *data;
 	struct stat sbuf;
 
 	if (argc != 2) {
@@ -34,17 +34,17 @@ int main(int argc, char *argv[])
 
 	offset = atoi(argv[1]);
 	if (offset < 0 || offset > sbuf.st_size-1) {
-		fprintf(stderr, "mmapdemo: offset must be in the range 0-%ld\n", sbuf.st_size-1);
+		fprintf(stderr, "mmapdemo: offset must be in the range 0-%lld\n", sbuf.st_size-1);
 		exit(1);
 	}
 
-	if ((data = mmap((caddr_t)0, sbuf.st_size, PROT_READ, MAP_SHARED, fd, 0)) == (caddr_t)(-1)) {
+	// Note that MAP_FAILED is (void*)(-1), but more readable
+	if ((data = mmap((void*)0, sbuf.st_size, PROT_READ, MAP_SHARED, fd, 0)) == MAP_FAILED) {
 		perror("mmap");
 		exit(1);
 	}
 
-	printf("byte at offset %d is '%c'\n", offset, data[offset]);
+	printf("byte at offset %d is '%c'\n", offset, ((char*)data)[offset]);
 
 	return 0;
 }
-

examples/pipe1.c

@@ -25,4 +25,3 @@ int main(void)
 
 	return 0;
 }
-

examples/pipe2.c

@@ -23,11 +23,13 @@ int main(void)
 		exit(0);
 	} else {
 		printf("PARENT: reading from pipe\n");
+		// This read blocks.  Fortunately, the child
+		// writes to it in non-blocking mode and then closes it,
+		// causing the OS trigger this process to wake up.
 		read(pfds[0], buf, 5);
 		printf("PARENT: read \"%s\"\n", buf);
 		wait(NULL);
 	}
 
 	return 0;
 }
-

examples/pipe3.c

@@ -13,17 +13,16 @@ int main(void)
 	pipe(pfds);
 
 	if (!fork()) {
-		close(1);       /* close normal stdout */
-		dup(pfds[1]);   /* make stdout same as pfds[1] */
+		dup2(pfds[1], 1); /* combines close() and dup(), atomically */
 		close(pfds[0]); /* we don't need this */
+		close(pfds[1]); /* we don't need this */
 		execlp("ls", "ls", NULL);
 	} else {
-		close(0);       /* close normal stdin */
-		dup(pfds[0]);   /* make stdin same as pfds[0] */
+		dup2(pfds[0], 0); /* combines close() and dup(), atomically */
+		close(pfds[0]); /* we don't need this */
 		close(pfds[1]); /* we don't need this */
 		execlp("wc", "wc", "-l", NULL);
 	}
 
 	return 0;
 }
-

examples/semdemo.c

@@ -12,11 +12,14 @@
 
 #define MAX_RETRIES 10
 
+#ifdef NEED_SEMUN
+/* Defined in sys/sem.h as required by POSIX now */
 union semun {
 	int val;
 	struct semid_ds *buf;
 	ushort *array;
 };
+#endif
 
 /*
 ** initsem() -- more-than-inspired by W. Richard Stevens' UNIX Network
@@ -27,7 +30,7 @@ int initsem(key_t key, int nsems)  /* key from ftok() */
 	int i;
 	union semun arg;
 	struct semid_ds buf;
-	struct sembuf sb;
+	struct sembuf sb = { 0 };  /* best to always init structs */
 	int semid;
 
 	semid = semget(key, nsems, IPC_CREAT | IPC_EXCL | 0666);
@@ -48,7 +51,6 @@ int initsem(key_t key, int nsems)  /* key from ftok() */
 				return -1; /* error, check errno */
 			}
 		}
-
 	} else if (errno == EEXIST) { /* someone else got it first */
 		int ready = 0;
 

examples/shmdemo.c

@@ -35,8 +35,12 @@ int main(int argc, char *argv[])
 	}
 
 	/* attach to the segment to get a pointer to it: */
+        /* note that 'void*' will be implicitly converted to 'char*' */
 	data = shmat(shmid, (void *)0, 0);
-	if (data == (char *)(-1)) {
+
+	/* we _could_ use MAP_FAILED, but technically that's not */
+	/* the defined return value.  System V failed on this one! */
+	if (data == (void *)(-1)) {
 		perror("shmat");
 		exit(1);
 	}
@@ -45,6 +49,7 @@ int main(int argc, char *argv[])
 	if (argc == 2) {
 		printf("writing to segment: \"%s\"\n", argv[1]);
 		strncpy(data, argv[1], SHM_SIZE);
+                data[SHM_SIZE-1] = '\0';
 	} else
 		printf("segment contains: \"%s\"\n", data);
 

examples/sigint.c

@@ -17,13 +17,11 @@ void sigint_handler(int sig)
 
 int main(void)
 {
-	void sigint_handler(int sig); /* prototype */
 	char s[200];
-	struct sigaction sa;
-
-	sa.sa_handler = sigint_handler;
-	sa.sa_flags = 0; // or SA_RESTART
-	sigemptyset(&sa.sa_mask);
+	struct sigaction sa = {
+	    .sa_handler = sigint_handler,
+	    .sa_flags = 0, // or SA_RESTART
+	};
 
 	if (sigaction(SIGINT, &sa, NULL) == -1) {
 		perror("sigaction");
@@ -39,4 +37,3 @@ int main(void)
 
 	return 0;
 }
-

examples/sigusr.c

@@ -19,14 +19,13 @@ void sigusr1_handler(int sig)
 
 int main(void)
 {
-	struct sigaction sa;
+	struct sigaction sa = {
+	    .sa_handler = sigusr1_handler,
+	    .sa_flags = 0, // or SA_RESTART
+	};
 
 	got_usr1 = 0;
 
-	sa.sa_handler = sigusr1_handler;
-	sa.sa_flags = 0;
-	sigemptyset(&sa.sa_mask);
-
 	if (sigaction(SIGUSR1, &sa, NULL) == -1) {
 		perror("sigaction");
 		exit(1);
@@ -41,4 +40,3 @@ int main(void)
 
 	return 0;
 }
-

examples/spock.c

@@ -42,4 +42,3 @@ int main(void)
 
 	return 0;
 }
-

examples/tick.c

@@ -25,7 +25,7 @@ int main(void)
 	printf("got a writer\n");
 
 	do {
-		if ((num = read(fd, s, 300)) == -1)
+		if ((num = read(fd, s, sizeof(s))) == -1)
 			perror("read");
 		else {
 			s[num] = '\0';