优化了命名

C13-Linux系统编程/io/sys/mycpy.c

@@ -0,0 +1,71 @@
+#include <fcntl.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+
+#define BUFSIZE 1024
+/**
+ * 可以用 time 命令找到 BUFSIZE 最佳值
+ *
+ * time ./mycpy /etc/services /tmp/out
+ */
+
+int main(int argc, char **argv)
+{
+    int  sfd, dfd;
+    char buf[BUFSIZE];
+    int  len, ret, pos;
+
+    if (argc < 3)
+    {
+        fprintf(stderr, "Usage: %s <src> <dst>\n", argv[0]);
+        exit(1);
+    }
+
+    sfd = open(argv[1], O_RDONLY);
+    if (sfd < 0)
+    {
+        perror("open");
+        exit(1);
+    }
+
+    dfd = open(argv[2], O_WRONLY | O_CREAT | O_TRUNC, 0600);
+    if (dfd < 0)
+    {
+        // !!!
+        close(sfd);
+        perror("open");
+        exit(1);
+    }
+
+    while (1)
+    {
+        len = read(sfd, buf, BUFSIZE);
+        if (len < 0)
+        {
+            perror("read");
+            break;
+        }
+        if (len == 0)
+            break;
+
+        pos = 0;
+        while (len > 0)
+        {
+            /* 可能没写完被别的中断打断 */
+            ret = write(dfd, buf + pos, len);
+            if (ret < 0)
+            {
+                perror("write");
+                exit(1);
+            }
+            pos += ret;
+            len -= ret;
+        }
+    }
+
+    close(dfd);
+    close(sfd);
+
+    exit(0);
+}