Added SMSD non-interactive command line client for Shack-Hartmann control system

pipe_and_buffering_read.c

@@ -0,0 +1,82 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <err.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <string.h>
+
+#define BUFSZ 1024
+
+static void getpath(const char *modname, char *buf, size_t bufsize){
+	int filedes[2];
+	char cmd[256];
+	ssize_t count;
+	snprintf(cmd, 255, "modinfo -F filename %s", modname);
+	if(pipe(filedes) == -1)
+		err(3, "pipe");
+	pid_t pid = fork();
+	if(pid == -1)
+		err(4, "fork");
+	else if (pid == 0){
+		while ((dup2(filedes[1], STDOUT_FILENO) == -1) && (errno == EINTR)) {}
+		close(filedes[1]);
+		close(filedes[0]);
+		system(cmd);
+		exit(0);
+	}
+	while(1){
+		count = read(filedes[0], buf, bufsize);
+		if(count == -1){
+			if(errno == EINTR)
+				continue;
+			else
+				err(7, "read");
+		}else
+			break;
+	}
+	if(count > 1) buf[count-1] = 0;
+	close(filedes[0]);
+	wait(0);
+}
+
+int main(){
+	int fd = open("/proc/modules", O_RDONLY);
+	if(fd < 0) err(1, "open");
+	char buf[BUFSZ+1], *end = buf;
+	size_t readed, toread = BUFSZ;
+	buf[BUFSZ] = 0;
+	while(1){
+		readed = read(fd, end, toread);
+		if(readed < 1 && end == buf) break;
+		end += readed;
+		*end = 0;
+		char *E;
+#define getspace(X)  {E = strchr(X, ' '); if(!E) break; *E = 0; E++;}
+		getspace(buf);
+		char *name = buf, *start = E;
+		if(start >= end) break;
+		getspace(start);
+#undef getspace
+		size_t size = atoll(start);
+		char path[1024];
+		getpath(name, path, sizeof(path));
+		printf("%s: %zd\n", path, size);
+		if(E < end){
+			if((start = strchr(E, '\n'))) start++;
+			else start = end;
+		}else start = E;
+		if(start < end){
+			readed = end - start;
+			memmove(buf, start, readed);
+			end = buf + readed;
+			toread = BUFSZ - readed;
+		}else{
+			toread = BUFSZ;
+			end = buf;
+		}
+	}
+	close(fd);
+	return 0;
+}