finish sh.c and update README.md

README.md

@@ -1,6 +1,6 @@
 # myxv6
 
-看代码并加上中文注释
+看代码并加上中文注释，还有就是做lab
 
 ## 环境
 
@@ -21,12 +21,17 @@
 
 所以不知道后面更新的qemu是否还能启动，
 
-所以记下现在运行的qemu版本：
+所以记下现在运行的版本：
 
-    $ brew info qemu
-    qemu: stable 6.0.0 (bottled), HEAD
-    Emulator for x86 and PowerPC
-    ...
+    $ riscv64-unknown-elf-gcc --version
+    riscv64-unknown-elf-gcc (GCC) 10.2.0
+    Copyright (C) 2020 Free Software Foundation, Inc.
+    This is free software; see the source for copying conditions.  There is NO
+    warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+
+    $ qemu-system-riscv64 --version
+    QEMU emulator version 6.0.0
+    Copyright (c) 2003-2021 Fabrice Bellard and the QEMU Project developers
 
 退出qemu:
 

user/sh.c

@@ -4,7 +4,7 @@
 #include "user/user.h"
 #include "kernel/fcntl.h"
 
-// Parsed command representation
+// 解析的命令表示
 #define EXEC  1
 #define REDIR 2
 #define PIPE  3
@@ -49,11 +49,11 @@ struct backcmd {
   struct cmd *cmd;
 };
 
-int fork1(void);  // Fork but panics on failure.
+int fork1(void);  // Fork 但如果错误则，恐慌(panic)
 void panic(char*);
 struct cmd *parsecmd(char*);
 
-// Execute cmd.  Never returns.
+// 执行命令，不会返回
 void
 runcmd(struct cmd *cmd)
 {
@@ -147,19 +147,19 @@ main(void)
   static char buf[100];
   int fd;
 
-  // Ensure that three file descriptors are open.
+  // 保证这三个文件描述符是打开的
   while((fd = open("console", O_RDWR)) >= 0){
     if(fd >= 3){
       close(fd);
       break;
     }
   }
 
-  // Read and run input commands.
+  // 读取和运行输入命令
   while(getcmd(buf, sizeof(buf)) >= 0){
     if(buf[0] == 'c' && buf[1] == 'd' && buf[2] == ' '){
-      // Chdir must be called by the parent, not the child.
-      buf[strlen(buf)-1] = 0;  // chop \n
+      // Chdir 必须被父调用，不能被子调用
+      buf[strlen(buf)-1] = 0;  // 去掉 \n
       if(chdir(buf+3) < 0)
         fprintf(2, "cannot cd %s\n", buf+3);
       continue;
@@ -190,7 +190,7 @@ fork1(void)
 }
 
 //PAGEBREAK!
-// Constructors
+// 构造cmd
 
 struct cmd*
 execcmd(void)
@@ -257,7 +257,7 @@ backcmd(struct cmd *subcmd)
   return (struct cmd*)cmd;
 }
 //PAGEBREAK!
-// Parsing
+// 解析
 
 char whitespace[] = " \t\r\n\v";
 char symbols[] = "<|>&;()";
@@ -445,7 +445,7 @@ parseexec(char **ps, char *es)
   return ret;
 }
 
-// NUL-terminate all the counted strings.
+// NUL终结所有字符串
 struct cmd*
 nulterminate(struct cmd *cmd)
 {