叉后失去控制() [英] Losing control after fork()
问题描述
我在写一个简单的程序,以更好地了解叉(),等待()和execvp()。我的问题是我运行程序后,控制不会回传给壳,我不知道为什么。我要的是能够输入另一个命令到外壳中的code完成后。我看了看<一个href=\"http://stackoverflow.com/questions/14793636/child-processes-wont-die-in-c-program?rq=1\">this,但我不认为这是适用于我的情况。我基本上只是复制的code从我的这里。
输入/输出(#是我打字行的前面,虽然不是输入的一部分):
壳GT; #GCC test.c以-o测试
外壳&GT; #./test
输入程序(LS)
#LS
输入ARG(。)
#。
测试test.c的extra.txt
#一个; dlghasdf
# 回去
#:(
我的code:
INT主要(无效){
//只是走和清洁输入
的printf(输入程序(LS)\\ n);
炭inputprogram [5] = {0,0,0,0,0};
与fgets(inputprogram,5,标准输入); //读取用户命令
INT I;
对于(I = 0; I&小于5;我++){
如果(inputprogram [I] =='\\ n'){
inputprogram [I] = 0;
}
} 的printf(输入ARG()\\ n);
炭inputarg [5] = {0,0,0,0,0};
与fgets(inputarg,5,标准输入); //读取用户命令
对于(I = 0; I&小于5;我++){
如果(inputarg [I] =='\\ n'){
inputarg [I] = 0;
}
} 每[] =炭{inputarg [0],0};
字符* ARG [] = {inputprogram,每次,NULL}; INT状态= 0;
将为pid_t的孩子; //叉(),execvp(),等待()
//////////////////////////////////
如果((子=叉())小于0){
/ * fork一个子进程* /
的printf(*** ERROR:分叉子进程失败\\ n);
出口(1);
}否则如果(孩子== 0){
execvp(inputprogram,ARG);
出口(1);
}其他{
而(等待(安培;状态=小孩)!);
} 返回EXIT_SUCCESS;
}
这行
而(等待(安培;!=状态子));
是不正确
您需要
等待(安培;状态);
或者使用 waitpid函数
- 请参阅这里
I'm writing a simple program to better understand fork(), wait(), and execvp(). My problem is that after I run the program, control is not passed back to the shell and I have no clue why. What I want is to be able to input another command into the shell after the code is finished. I took a look at this, but I don't think it's applicable in my case. I've basically just the copied code I found from here.
input/output (# is in front of lines I typed, though is not part of the input):
shell> # gcc test.c -o test
shell> # ./test
input program (ls)
# ls
input arg (.)
# .
test test.c extra.txt
# a;dlghasdf
# go back
# :(
my code:
int main(void) {
//just taking and cleaning input
printf("input program (ls)\n");
char inputprogram [5] = {0,0,0,0,0};
fgets(inputprogram,5,stdin); //read in user command
int i;
for(i = 0; i < 5; i++) {
if(inputprogram [i] == '\n' ){
inputprogram[i] = 0;
}
}
printf("input arg (.)\n");
char inputarg [5] = {0,0,0,0,0};
fgets(inputarg,5,stdin); //read in user command
for(i = 0; i < 5; i++) {
if(inputarg [i] == '\n' ){
inputarg[i] = 0;
}
}
char per []= {inputarg[0], 0};
char *arg [] = {inputprogram, per , NULL};
int status = 0;
pid_t child;
//the fork(), execvp(), wait()
//////////////////////////////////
if ((child = fork()) < 0) {
/* fork a child process */
printf("*** ERROR: forking child process failed\n");
exit(1);
} else if(child == 0){
execvp(inputprogram, arg);
exit(1);
} else {
while(wait(&status != child));
}
return EXIT_SUCCESS;
}
This line
while(wait(&status != child));
is incorrect
You need
wait(&status);
Or use waitpid
- See here
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