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我必須製作簡單的shell來讀取命令並按順序執行它們。條件不改變主函數的形式,並且執行函數應該是遞歸的。 主要問題是,它似乎waitpid不起作用。但我知道,我的代碼中存在很多問題。請讓我知道我應該從哪裏開始..簡單的shell在c:waitpid系統調用不起作用
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/wait.h>
#define MAX 10
char cmmd[MAX][256];
int sp;
char *argv[10];
int size;
void ClearLineFromReadBuffer(void){
while(getchar() != '\n');
}
void printCommands(){
size = sp+1;
//print by moving stack pointer
while(1){
if (sp==-1) break;
printf("Command line : %s\n", cmmd[sp]);
sp--;
}
printf("print end\n");
}
void readCommandLines(){
int a = 0; //return of scanf
while (1){ //write commends to cmmd untill get ctrl+d
printf(">");
a = (scanf("%[^\n]s", cmmd[sp])); //take input to str untill get enter(scanf returns -1)
if (a==-1) {sp--; break;}
if (a==1) ClearLineFromReadBuffer();
if (a==0) {printf("error"); break;}
sp++;
}
printf("\n");
}
void readACommand(char *line){ //line takes string's name.
int i=0;
argv[i]=strtok(line," "); //i==0
while(strtok(line," ")!=NULL){
i++;
argv[i]=strtok(NULL," ");
}
printf("%s",argv[0]);
printf("%s",argv[1]);
}
void executeCommands(){ //Recursive function
int n = sp;
n++;
printf("%d",n);
printf("%s",cmmd[n]);
char *cmd_line = cmmd[n]; //command line which child process will execute
unsigned int child_pid; //fork() returns process id of child in parents process
int status; //status takes return of child's exit()
child_pid=fork();
if (child_pid != 0){ // Parents process
printf("parents access");
waitpid(child_pid,&status,0);
printf("***Process %d Child process %d DONE with status %x\n\n",getpid(),child_pid,status);
sp++;
if(sp<size)
executeCommands();
}
else if (child_pid == 0){ //fork() returns 0 in child process
printf("***Process %d Executing Command %s",getpid(),cmd_line);
readACommand(cmmd[n]);
execve(argv[0],argv,NULL);
printf("ERROR - not executing command \"%s\"\n",argv[0]); //can be printed because exec() failed
}
}
int main(){
readCommandLines();
printCommands();
executeCommands();
return(0);
}
這是結果。 enter image description here
可能相關:你必須'NULL'終止你的參數列表。 –
您的令牌循環非常可疑。如果超過2個參數,我認爲它可能是無限的。它不會以NULL結尾。 –
Thanl你。我修好了,併成功分開它,但循環永遠不會結束。你能告訴我什麼是重要的嗎?當我嘗試打印每個argv時,它可以打印到最後一個參數,但仍然保留在while循環中。 –