add directory study

study/linux-travel/MINIX-1.5/1.5/Source/commands/lpr.c

@@ -0,0 +1,110 @@
+/* lpr - line printer front end		Author: Andy Tanenbaum */
+
+#include <errno.h>
+#include <sys/types.h>
+#include <fcntl.h>
+
+#define BLOCK 1024
+
+char in_buf[BLOCK], out_buf[BLOCK];
+int cur_in, in_count, out_count, column;
+
+main(argc, argv)
+int argc;
+char *argv[];
+{
+/* This program copies files to the line printer.  It expands tabs and converts
+ * line feeds to carriage returns + line feeds.
+ */
+
+  int i, fd;
+
+  close(1);
+  if (open("/dev/lp", O_WRONLY) < 0) {
+	std_err("lpr: can't open /dev/lp\n");
+	exit(1);
+  }
+  if (argc == 1) {
+	copy(0);		/* standard input only */
+  } else {
+	for (i = 1; i < argc; i++) {
+		if ((fd = open(argv[i], O_RDONLY)) < 0) {
+			std_err("lpr: can't open ");
+			std_err(argv[1]);
+			std_err("\n");
+			exit(1);
+		} else {
+			copy(fd);
+			close(fd);
+			cur_in = 0;
+			in_count = 0;
+		}
+	}
+  }
+  exit(0);
+}
+
+
+copy(fd)
+int fd;
+{
+/* Print a file, adding carriage returns and expanding tabs. */
+
+  char c;
+
+  while (1) {
+	if (cur_in == in_count) {
+		in_count = read(fd, in_buf, BLOCK);
+		if (in_count == 0) {
+			flush();
+			return;
+		}
+		cur_in = 0;
+	}
+	c = in_buf[cur_in++];
+	if (c == '\n') {
+		putc('\r');
+		putc('\n');
+	} else if (c == '\t') {
+		do {
+			putc(' ');
+		} while (column & 07);
+	} else
+		putc(c);
+  }
+}
+
+putc(c)
+char c;
+{
+  out_buf[out_count++] = c;
+  if (c == '\n')
+	column = 0;
+  else
+	column++;
+  if (out_count == BLOCK) {
+	flush();
+  }
+}
+
+flush()
+{
+  int n, count = 0;
+
+  if (out_count == 0) return;
+  while (1) {
+	n = write(1, out_buf, out_count);
+	if (n == out_count) break;
+	if (n != EAGAIN) {
+		std_err("Printer error\n");
+		exit(1);
+	}
+	if (count > 5) {
+		std_err("Printer keeps returning busy status\n");
+		exit(1);
+	}
+	count++;
+	sleep(1);
+  }
+  out_count = 0;
+}