chapter 8 sample code to 8.5

Author: Heatwave

chapter-8-the-unix-system-interface/cp.c

@@ -0,0 +1,41 @@
+#include <stdio.h>
+#include <fcntl.h>
+#include <unistd.h> 
+#include <stdarg.h>
+#include <stdlib.h>
+
+#define PERMS 0666
+
+void error(char *fmt, ...);
+
+main(int argc, char *argv[])
+{
+	int f1, f2, n;
+	char buf[BUFSIZ];
+
+	if (argc != 3)
+		error("usage: cp from to");
+	if ((f1 = open(argv[1], O_RDONLY, 0)) == -1)
+		error("cp: can't open %s", argv[1]);
+	if ((f2 = open(argv[2], PERMS, 0)) == -1)
+		error("cp: can't create %s, mode %03o", argv[2], PERMS);
+
+	while ((n = read(f1, buf, BUFSIZ)) > 0)
+		if (write(f2, buf, n) != n)
+			error("cp: write error on file %s", argv[2]);
+	
+	return 0;
+}
+
+void error(char *fmt, ...)
+{
+	va_list args;
+
+	va_start(args, fmt);
+	fprintf(stderr, "error: ");
+	vfprintf(stderr, fmt, args);
+	fprintf(stderr, "\n");
+	va_end(args);
+	exit(1);
+}
+

chapter-8-the-unix-system-interface/fopen.c

@@ -0,0 +1,99 @@
+#include <fcntl.h>
+#include <unistd.h> 
+#include <stdlib.h> 
+#include <assert.h> 
+
+//#define NULL		0
+#define EOF			(-1)
+#define BUFSIZ		1024
+#define OPEN_MAX	20
+
+#define PERMS 0666
+
+typedef struct _iobuf {
+	int cnt;
+	char *ptr;
+	char *base;
+	int flag;
+	int fd;
+} FILE;
+
+FILE _iob[OPEN_MAX];
+
+enum _flags {
+	_READ	= 01,
+	_WRITE	= 02,
+	_UNBUF	= 04,
+	_EOF	= 010,
+	_ERR	= 020
+};
+
+FILE *fopen(char *name, char *mode);
+int _fillbuf(FILE *fp);
+
+int main()
+{
+	FILE *fp = fopen("fopen.c", "rw");
+	assert(fp != NULL);
+	return 0;
+}
+
+FILE *fopen(char *name, char *mode)
+{
+	int fd;
+	FILE *fp;
+
+	if (*mode != 'r' && *mode != 'w' && *mode != 'a')
+		return NULL;
+	for (fp = _iob; fp < _iob + OPEN_MAX; fp++)
+		if ((fp->flag & (_READ | _WRITE)) == 0)
+			break;
+	if (fp >= _iob + OPEN_MAX)
+		return NULL;
+	
+	if (*mode == 'w')
+		fd = creat(name, PERMS);
+	else if (*mode == 'a') {
+		if ((fd = open(name, O_WRONLY, 0)) == -1)
+			fd = creat(name, PERMS);
+		lseek(fd, 0L, 2);
+	} else
+		fd = open(name, O_RDONLY, 0);
+	if (fd == -1)
+		return NULL;
+	fp->fd = fd;
+	fp->cnt = 0;
+	fp->base = NULL;
+	fp->flag = (*mode == 'r') ? _READ : _WRITE;
+	return fp;
+}
+
+int _fillbuf(FILE *fp)
+{
+	int bufsize;
+
+	if ((fp->flag & (_READ | EOF | _ERR)) != _READ)
+		return EOF;
+	bufsize = (fp->flag & _UNBUF) ? 1 : BUFSIZ;
+	if (fp->base == NULL)
+		if ((fp->base = (char *) malloc(bufsize)) == NULL)
+			return EOF;
+	fp->ptr = fp->base;
+	fp->cnt = read(fp->fd, fp->ptr, bufsize);
+	if (--fp->cnt < 0) {
+		if (fp->cnt == -1)
+			fp->flag |= _EOF;
+		else
+			fp->flag |= _ERR;
+		fp->cnt = 0;
+		return EOF;
+	}
+	return (unsigned char) *fp->ptr++;
+}
+
+FILE _iob[OPEN_MAX] = {
+	{ 0, (char *) 0, (char *) 0, _READ, 0 },
+	{ 0, (char *) 0, (char *) 0, _WRITE, 1 },
+	{ 0, (char *) 0, (char *) 0, _WRITE | _UNBUF, 2 },
+};
+

chapter-8-the-unix-system-interface/sys-copy.c

@@ -0,0 +1,13 @@
+#include <unistd.h> 
+#include <stdio.h> 
+
+main()
+{
+	char buf[BUFSIZ];
+	int n;
+
+	while ((n = read(0, buf, BUFSIZ)) > 0)
+		write(1, buf, n);
+	return 0;
+}
+