我在另一个 shell 中运行这个基本的 shell 程序。我无法弄清楚为什么我的 shell 在“ls”执行后没有继续运行。我没有出口，但它会回到原来的外壳。如果想使用它，我每次都必须运行我的 shell 程序。我认为这就是 fork() 应该做的。我只希望我的 shell 使用我用 if else 语句编写的 exit 命令退出。任何建议将不胜感激。哦，忽略 gettoks() 解析器函数，我不知道如何将它用于输入，所以我为字符串输入 cmSTR 编写了 if else 语句，而不是使用 gettoks() 解析器。主要是因为我不知道如何将输入传递给它
#include <iostream>
#include <unistd.h>
#include <sys/types.h>
#include <errno.h>
#include <signal.h>
#include <cstdlib>
#include <sys/wait.h>
using namespace std;
// Initializing counters for trapping
static int cc_counter = 0;
static int cz_counter = 0;
static int cq_counter = 0;
//Functions for trap signal handler
void cc_handler( int signo )
{
++cc_counter;
}
void cz_handler( int signo )
{
++cz_counter;
}
void cq_handler( int signo )
{
++cq_counter;
}
//*********************************************************
//
// Extern Declarations
//
//*********************************************************
using namespace std;
extern "C"
{
extern char **gettoks();
}
//*********************************************************
//
// Main Function
//
//*********************************************************
int main( int argc, char *argv[] )
{
// local variables
int ii;
char **toks;
int retval;
// initialize local variables
ii = 0;
toks = NULL;
retval = 0;
char buf[1000];//Initialize of size for current working directory
string cmSTR;//String to hold input
int status;//Initialization of status for fork()
pid_t pid;//Declaration of pid
// main (infinite) loop
while( true )
{
signal( SIGINT, cc_handler );// Traps Ctrl+C
signal( SIGTSTP, cz_handler);// Traps Ctrl+Z
signal( SIGQUIT, cq_handler);// Traps Ctrl+\
//prompt and show current working directory
cout <<("RS_SHELL:") << getcwd(buf,1000) << "\t";
getline(cin ,cmSTR);//read input from keyboard
// if else loop to switch based on command input
if(cmSTR == "ls")// if ls, then execute arguement
{
execl( "/bin/ls", "ls", NULL );//System call to execute ls
}
else if(cmSTR == "exit")//if exit, then execute block of code
{
cout << "Ctrl C entered: " << ++cc_counter << "times"<< endl;
cout << "Ctrl Z entered: " << ++cz_counter << "times"<< endl;
cout << "Ctrl Back Slash entered: " << ++cq_counter << "times"<< endl;
exit(1);
}
else if(cmSTR == "guish")// if guish, execute guish shell
{
execvp("guish", NULL);
}
//if input is not any of previous commands then fork()
else if(cmSTR != "ls" && cmSTR != "exit" && cmSTR != "guish" && cmSTR != "\n")
{
pid = fork();
if (pid < 0)//Loop to fork parent and child process
{
fprintf(stderr, "Fork Failed");
exit(-1);
}
else if (pid == 0)//Child process
{
execvp("guish", NULL);//system call to execute guish shell
}
else //Parent process
{
waitpid( -1, &status,0);
exit(0);
}
}
// get arguments
toks = gettoks();
if( toks[0] != NULL )
{
// simple loop to echo all arguments
for( ii=0; toks[ii] != NULL; ii++ )
{
cout << "Argument " << ii << ": " << toks[ii] << endl;
}
if( !strcmp( toks[0], "exit" ))
break;
}
}
// return to calling environment
return( retval );
}