#include?
#include?
#include?
#include?
#include?
#include?
#include?
#include?

//?Simplifed?xv6?shell.

#define?MAXARGS?10

//?All?commands?have?at?least?a?type.?Have?looked?at?the?type?the?code
//?typically?casts?the?*cmd?to?some?specific?cmd?type.
struct?cmd?{
??int?type;??????????//??‘?‘?（exec）?|?（pipe）?‘<‘?or?‘>‘?for?redirection
};

struct?execcmd?{
??int?type;??????????????//?‘?‘
??char?*argv[MAXARGS];???//?arguments?to?the?command?to?be?exec-ed
};

struct?redircmd?{
??int?type;??????????//?
??struct?cmd?*cmd;???//?the?command?to?be?run?（e.g.?an?execcmd）
??char?*file;????????//?the?input/output?file
??int?mode;??????????//?the?mode?to?open?the?file?with
??int?fd;????????????//?the?file?descriptor?number?to?use?for?the?file
};

struct?pipecmd?{
??int?type;??????????//?|
??struct?cmd?*left;??//?left?side?of?pipe
??struct?cmd?*right;?//?right?side?of?pipe
};

int?fork1（void）;??//?Fork?but?exits?on?failure.
struct?cmd?*parsecmd（char*）;

//運行cmd，Never?returns.
void?runcmd（struct?cmd?*cmd）
{
??int?p[2]?r;
??struct?execcmd?*ecmd;
??struct?pipecmd?*pcmd;
??struct?redircmd?*rcmd;

??if（cmd?==?0）
??{
??????exit（0）;
??}

??switch（cmd->type）
??{
??default:
????fprintf（stderr?“unknown?runcmd\n“）;
????exit（-1）;

??case?‘?‘:
????ecmd?=?（struct?execcmd*）cmd;
????if（ecmd->argv[0]?==?0）
????{
????????exit（0）;
????}

????//fprintf（stderr?“exec?not?implemented\n“）;
????//?Your?code?here?...

????//在當前目錄下搜索執行文件失敗
????if（execv（ecmd->argv[0]?ecmd->argv）?==?-1）
????{
????????//更換為/bin/目錄
????????char?cmdPath[30]?=?“/bin/“;

????????//連接字符串/bin/與之前的目錄
????????strcat（cmdPath?ecmd?->?argv[0]）;

????????//在/bin/目錄下搜索執行文件失敗
????????if（execv（cmdPath?ecmd->argv）?==?-1）
????????{
????????????//更換為/usr/bin/目錄
????????????char?cmdPath2[30]?=?“/usr/bin/“;

????????????//連接字符串/usr/bin/與最初的目錄
????????????strcat（cmdPath2?ecmd?->?argv[0]）;

????????????//更換為/usr/bin/目錄搜索執行文件失敗
????????????if（execv（cmdPath2?ecmd->argv）?==?-1）
????????????{
????????????????//執行文件不存在，結束當前進程
????????????????fprintf（stderr?“Can‘t?found?file:?%s%d\n“?ecmd?->?argv[0]?__LINE__）;
????????????????exit（0）;
????????????}
????????}
????}
????break;
????
????/*
????//如果有權限訪問文件且文件存在
????if（access（ecmd->argv[0]F_OK）?==?0）
????{
????????//找到可執行文件
????????execv（ecmd->argv[0]?ecmd->argv）;
????}

????else
????{
????????//有權限訪問文件，將當前的工作目錄改變成/bin/目錄搜索失敗
????????if（chdir（“/bin/“）?????????{
????????????//文件不存在，結束當前進程
????????????printf（“Can‘t?change?directory?%d\n“?__LINE__）;
????????????exit（0）;
????????}

????????//有權限訪問文件，在/bin/搜索可執行文件成功
????????execv（ecmd->argv[0]?ecmd->argv）;
????}

????//既無權限，執行文件又不存在，結束當前進程
????fprintf（stderr?“Can‘t?find?file:?%s?%d\n“?ecmd->argv[0]?__LINE__）;
????
????break;
????*/

??case?‘>‘:
??case?‘<‘:
????rcmd?=?（struct?redircmd*）cmd;
????//fprintf（stderr?“redir?not?implemented\n“）;
????//?Your?code?here?...

????//‘<‘為0，‘>’為1
????close（rcmd->fd）;

?????//open（）函數，對產生的新文件賦

?屬性????????????大小?????日期????時間???名稱
-----------?---------??----------?-----??----
?????目錄???????????0??2018-09-17?20:06??lab1\
?????文件???????10827??2017-10-19?22:15??lab1\lab1.c
?????目錄???????????0??2018-09-17?20:06??lab2\
?????文件????????1569??2017-10-31?21:46??lab2\lab2.c
?????文件?????1652440??2018-09-17?20:11??主存管理實驗報告.doc
?????文件?????2084546??2018-09-17?20:11??文件管理實驗報告.doc