在Kill中實現EINVAL，EPERM，ESRCH（）

Question

我想在我的程序中實現EINVAL，EPERM，ESRCH。

ERRORS
EINVAL An invalid signal was specified.
EPERM The process does not have permission to send the signal to any of the target processes. ESRCH The pid or process group does not exist.

這裏是我的源代碼：

#include <stdio.h> 
#include <sys/types.h> 
#include <signal.h> 
#include <unistd.h> 

int main(void) 
{ 

int errno, pid; 

puts("Enter a process id : "); 
scanf("%d", &pid); 

    errno = kill(pid, 1); 

if(errno == -1) 
{ 
    printf("Cannot find or kill the specified process\n"); 

} 


switch(errno) 
{ 
    case EINVAL: 
    printf("An invalid signal was specified.\n"); 
    break; 

    case EPERM: 
    printf("The process does not have permission to send the signal to any of the target processes.\n"); 
    break; 

    case ESRCH: 
    printf("The pid or process group does not exist."); 
    break; 
} 

} 

當我編譯程序，我得到以下錯誤。

unipro@ubuguest:/SoftDev/ADSD/Module 1/Unit 1/Pratice/C/C_adv/unix$ cc killApp.c -o killApp
killApp.c: In function ‘main’:
killApp.c:29: error: ‘EINVAL’ undeclared (first use in this function)
killApp.c:29: error: (Each undeclared identifier is reported only once
killApp.c:29: error: for each function it appears in.)
killApp.c:33: error: ‘EPERM’ undeclared (first use in this function)
killApp.c:37: error: ‘ESRCH’ undeclared (first use in this function)
unipro@ubuguest:/SoftDev/ADSD/Module 1/Unit 1/Pratice/C/C_adv/unix$

那麼EINVAL，EPERM，ESRCH定義在哪裏？我是否需要定義任何額外的頭文件？或者我正在以一種錯誤的方式實施它？

更新的代碼[工作代碼]：

#include <stdio.h> 
#include <sys/types.h> 
#include <signal.h> 
#include <unistd.h> 
#include <errno.h> 

int main(void) 
{ 

    int status, pid; 

    puts("Enter a process id : "); 
    scanf("%d", &pid); 

    status = kill(pid, 1); 



    switch(errno) 
    { 
     case EINVAL: 
      printf("An invalid signal was specified.\n"); 
      break; 

     case EPERM: 
      printf("The process does not have permission to send the signal to any of the target processes.\n"); 
      break; 

     case ESRCH: 
      printf("The pid or process group does not exist."); 
      break; 
    } 

} 

感謝。

Answer 1

你正在試圖做的都不行什麼，首先你應該#include <errno.h>（因爲這就是errno定義，爲是錯誤代碼）。 其次，不要調用你的本地返回值變量errno（因爲它存在並且是錯誤代碼的位置）。

例如。

#include <errno.h> 
/* ... */ 

int rc; 
/* ... */ 

rc = kill(pid, SIGHUP); 
if (rc != 0) 
{ 
    switch (errno) {...} 
}