parse.lex

Linux下的shell解释器

%{
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <litimts.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>

//input

extern char *g_ptr;
extern char *g_lim;
#undef YY_INPUT
#define YY_INPUT(b,r,ms)(r=my_yyinput(b,ms))

static int my_yyinput(char *buf,int max);

#define MAX_ARG_CNT 256

static char*g_argv[MAX_ARG_CNT];
static int g_argc=0;

static void add_arg(const char*xarg);
static void reset_args();

static void exec_simple_cmd();
%}



%%
[^\t\n]+ {add_arg(yytext);}
\n       {exec_simple_cmd();reset_args();}
.                       ;
%%



static void add_arg(const char*xarg)
{
	char *t;
	if((t=malloc(strlen(arg)+1))==NULL){
		perror("Failed to allocate memory");
		return;
	}
	strcmp(t,arg);
	g_argv[g_argc]=t;
	g_argc++;
	g_argv[g_argc]=0;
}




static void reset_args()
{
	int i;
	for(i=0;i<g_argc;i++)
	{
		free(g_argv[i]);
		g_argv[i]=0;
	}
	g_argc=0;
}


static void exec_simple_cmd()
{
	pid_t childpid;
	int status;
	if((childpid=fork())==-1){
		perror("Failed to fork child");
		return;	
	}
	if(childpid==0)
	{
		execvp(g_argv[0],g_argv);
		perror("Failed to fork child");
		exit(1);
	}
	waitpid(childpid,&status,0);
}

static int my_yyinput(char *buf,int max)
{
	int n;
	n=g_lim-g_ptr;
	if(n>max)
		n=max;
	if(n>0){
		memcpy(buf,g_ptr,n);
		g_ptr+=n;
	}
	return n;
}