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c - 如何从 PROC 获取有关子进程的信息

问题描述

我正在尝试编写一个将几个进程作为参数的程序。然后父进程执行每个子进程并打印出一些关于它们的统计信息。

示例：/generate ls -l //将导致程序打印出一些关于 ls -l 的统计信息（特别是它的系统时间、用户时间和上下文切换次数）。

我不想使用 getrusage() 函数，而是想从 Proc 文件系统中获取必要的信息。现在我的理解是，如果我要使用 wait() 函数，它最终会从我的 proc 文件系统中删除信息。我在下面包含了我的代码

#include <time.h>
#include <stdbool.h>
#include <assert.h>
#include <errno.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <sys/resource.h>



void inputted_command(int a, char **b){
 for(int i=1;i<a;i++)
     printf("%s ",b[i]);


}

int main(int argc, char **argv){
    int status; 
  pid_t childpid;
  pid_t get_information;
if (argc < 2)
    {

        return 1;
    }

    bool handle_signals = (signal(SIGINT, SIG_IGN) != SIG_IGN); 
    clock_t t; 
    t= clock(); 
    pid_t pid = fork();

if(pid<0) 
{
printf("fork: error no = %s\n",strerror(errno));
 return 1;

}
else if(pid>0){
    signal(SIGINT,SIG_IGN); 

  sleep(60);

  /*
   get_information=fork();
   if(get_information==0){
     execlp(___);

   }else
  waitpid(pid, &status, 0); 



  */
  waitpid(childpid, &status, 0); 

    t= clock()-t; 
    double real_time_taken = ((double)t)/CLOCKS_PER_SEC;

  printf("The command "); 
  inputted_command(argc,argv);
  if(WIFSIGNALED(status)){

  printf("is interrupted by the signal number = %d (Insert Name Here) real: %.2f, user: , system: , context switch:  \n",WTERMSIG(status),real_time_taken);

}

else{

printf("terminated with return status code = %d real: %.2f, user: , system: , context switch:  \n",WEXITSTATUS(status), real_time_taken);

}

}

else if(pid==0){
       childpid=getpid();
        printf("Process with id: %d created for the command: ",(int)getpid());
        inputted_command(argc,argv);
        printf("\n");
        assert(pid == 0); 
        if (handle_signals) 
        signal(SIGINT, SIG_DFL);
        execvp(argv[1], &argv[1]); 
        printf(" experienced an error in starting the command: ");
        inputted_command(argc,argv);
        printf("\n");
        exit(-1);
      }

}

所以我的主要问题是，这是否是获取子进程信息的合适方式以及如何获取信息（主要是系统时间、用户时间以及自愿和非自愿上下文切换？

标签： clinuxprocesschild-process

解决方案

在Craig Estey的回答的推动下，在我的评论之后，并使用来自 POSIX for 的信息sigaction()，它指向Signal Actions 和<signal.h>，我想出了以下代码，它使用信号SA_SIGINFO处理SIGCHLD，允许程序收集/proc在子进程终止之后但在等待之前，来自文件系统的信息。

siginfo47.c

#define _XOPEN_SOURCE 700

#include "stderr.h"
#include <assert.h>
#include <errno.h>
#include <fcntl.h>
#include <inttypes.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/wait.h>
#include <unistd.h>

static int       got_signal = 0;
static siginfo_t child_info = { 0 };

static void sigchld(int signum, siginfo_t *info, void *ctxt)
{
    assert(info != 0);
    assert(ctxt != 0);
    assert(signum == info->si_signo);
    got_signal = signum;
    child_info = *info;
}

struct si_code_names
{
    int     si_code;
    char    si_code_name[16];
    char    si_code_meaning[64];
};

static struct si_code_names si_codes[] =
{
    [CLD_EXITED]    = { CLD_EXITED,    "CLD_EXITED",    "Child has exited." },
    [CLD_KILLED]    = { CLD_KILLED,    "CLD_KILLED",    "Child has terminated abnormally and did not create a core file." },
    [CLD_DUMPED]    = { CLD_DUMPED,    "CLD_DUMPED",    "Child has terminated abnormally and created a core file." },
    [CLD_TRAPPED]   = { CLD_TRAPPED,   "CLD_TRAPPED",   "Traced child has trapped." },
    [CLD_STOPPED]   = { CLD_STOPPED,   "CLD_STOPPED",   "Child has stopped." },
    [CLD_CONTINUED] = { CLD_CONTINUED, "CLD_CONTINUED", "Stopped child has continued." },
};

static void cat_proc_file(int pid, const char *base)
{
    char buffer[1024];
    int rc;
    rc = snprintf(buffer, sizeof(buffer), "/proc/%d/%s", pid, base);
    if (rc < 0 || rc >= (int)sizeof(buffer))
        err_error("snprintf() failed - can't happen!?!\n");
    int fd = open(buffer, O_RDONLY);
    if (fd < 0)
        err_syserr("failed to open file '%s' for reading: ", buffer);
    printf("Contents of %s:\n", buffer);
    int nbytes;
    while ((nbytes = read(fd, buffer, sizeof(buffer))) > 0)
        printf("%*.*s", nbytes, nbytes, buffer);
    putchar('\n');
    fflush(stdout);
    close(fd);
}

int main(int argc, char **argv)
{
    char *cmdv[] = { "ls", "-l", 0 };
    err_setarg0(argv[0]);
    if (argc <= 1)
    {
        argc = 2;
        argv = cmdv;
    }
    else
    {
        argc--;
        argv++;
    }

    pid_t pid = fork();

    if (pid < 0)
        err_syserr("failed to fork: ");
    else if (pid > 0)
    {
        struct sigaction sa = { 0 };
        sa.sa_sigaction = sigchld;
        sa.sa_flags = SA_SIGINFO;
        if (sigaction(SIGCHLD, &sa, 0) != 0)
            err_syserr("failed to set signal handling: ");

        printf("Parent PID %d: pausing while PID %d runs\n", (int)getpid(), (int)pid);
        fflush(stdout);
        pause();
        printf("Parent PID %d: unpaused\n", (int)getpid());

        printf("Stashed information:\n");
        printf("  Signal:       %d\n", got_signal);
        printf("  si_signo:     %d\n", child_info.si_signo);
        printf("  si_code:      %d\n", child_info.si_code);
        if (child_info.si_signo == SIGCHLD)
        {
            struct si_code_names *code = &si_codes[child_info.si_code];
            printf("                [%s] %s\n", code->si_code_name,
                   code->si_code_meaning);
        }
        printf("  si_pid:       %d\n", (int)child_info.si_pid);
        printf("  si_uid:       %d\n", (int)child_info.si_uid);
        printf("  si_addr:      0x%12" PRIXPTR "\n", (uintptr_t)child_info.si_addr);
        printf("  si_status:    %d\n", child_info.si_code);
        printf("  si_value.int: %d\n", child_info.si_value.sival_int);

        cat_proc_file(pid, "stat");
        cat_proc_file(pid, "status");

        int status;
        int corpse;
        if ((corpse = waitpid(pid, &status, 0)) != pid)
            err_syserr("failed to wait for child %d", pid);

        if (WIFSIGNALED(status))
            printf("PID %d died from signal number = %d (0x%.4X)\n",
                   corpse, WTERMSIG(status), status);
        else if (WIFEXITED(status))
            printf("PID %d exited normally with status = %d (0x%.4X)\n",
                   corpse, WEXITSTATUS(status), status);
        else
            printf("PID %d was neither signalled nor exited normally (0x%.4X)\n",
                   corpse, status);
    }
    else if (pid == 0)
    {
        printf("PID: %d:", (int)getpid());
        for (int i = 0; argv[i] != 0; i++)
            printf(" %s", argv[i]);
        putchar('\n');
        fflush(stdout);
        execvp(argv[0], &argv[0]);
        err_syserr("failed to execute %s: ", argv[0]);
        /*NOTREACHED*/
    }
}

其中一些代码可在我的 GitHub 上的SOQ （堆栈溢出问题）存储库中找到。具体来说，这些文件stderr.c可以stderr.h在src/libsoq子目录中找到。它们极大地简化了错误报告。

示例运行包括：

$ siginfo47
Parent PID 15016: pausing while PID 15017 runs
PID: 15017: ls -l
total 400
drwxr-xr-x   2 jleffler pd  4096 Oct 21 15:16 bin
drwxr-xr-x   5 jleffler pd   256 Oct 21 15:15 doc
drwxr-xr-x   2 jleffler pd  4096 Oct 21 15:15 etc
drwxr-xr-x   2 jleffler pd  4096 Oct 21 15:16 inc
drwxr-xr-x   2 jleffler pd   256 Oct 21 15:16 lib
-rw-r--r--   1 jleffler pd 22072 Oct 21 15:15 LICENSE.md
-rw-r--r--   1 jleffler pd   390 Oct 21 15:15 makefile
drwxr-xr-x   2 jleffler pd   256 Oct 21 15:15 packages
-rw-r--r--   1 jleffler pd  2694 Oct 21 15:15 README.md
-rwxr-xr-x   1 jleffler pd 64968 Oct 21 15:17 siginfo41
-rw-r--r--   1 jleffler pd  5990 Oct 21 15:17 siginfo41.c
-rwxr-xr-x   1 jleffler pd 66104 Oct 21 15:34 siginfo47
-rw-r--r--   1 jleffler pd  7417 Oct 21 15:33 siginfo47.c
drwxr-xr-x 230 jleffler pd  8192 Oct 21 15:15 src
Parent PID 15016: unpaused
Stashed information:
  Signal:       17
  si_signo:     17
  si_code:      1
                [CLD_EXITED] Child has exited.
  si_pid:       15017
  si_uid:       9508
  si_addr:      0x252400003AA9
  si_status:    1
  si_value.int: 0
Contents of /proc/15017/stat:
15017 (ls) Z 15016 15016 13211 34827 15016 4227084 452 0 0 0 0 0 0 0 20 0 1 0 511347844 0 0 18446744073709551615 0 0 0 0 0 0 0 0 0 18446744073709551615 0 0 17 6 0 0 0 0 0 0 0 0 0 0 0 0 0

Contents of /proc/15017/status:
Name:   ls
State:  Z (zombie)
Tgid:   15017
Ngid:   0
Pid:    15017
PPid:   15016
TracerPid:  0
Uid:    9508    9508    9508    9508
Gid:    1240    1240    1240    1240
FDSize: 0
Groups: 297 1240 1360 8714 
Threads:    1
SigQ:   0/71487
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000000000
SigCgt: 0000000180000000
CapInh: 0000000000000000
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: 0000001fffffffff
CapAmb: 0000000000000000
Seccomp:    0
Cpus_allowed:   ff
Cpus_allowed_list:  0-7
Mems_allowed:   00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000001
Mems_allowed_list:  0
voluntary_ctxt_switches:    3
nonvoluntary_ctxt_switches: 1

PID 15017 exited normally with status = 0 (0x0000)
$ siginfo47 exitcode 23
Parent PID 15032: pausing while PID 15033 runs
PID: 15033: exitcode 23
Parent PID 15032: unpaused
Stashed information:
  Signal:       17
  si_signo:     17
  si_code:      1
                [CLD_EXITED] Child has exited.
  si_pid:       15033
  si_uid:       9508
  si_addr:      0x252400003AB9
  si_status:    1
  si_value.int: 23
Contents of /proc/15033/stat:
15033 (exitcode) Z 15032 15032 13211 34827 15032 4227084 179 0 0 0 0 0 0 0 20 0 1 0 511349111 0 0 18446744073709551615 0 0 0 0 0 0 0 0 0 18446744073709551615 0 0 17 5 0 0 0 0 0 0 0 0 0 0 0 0 0

Contents of /proc/15033/status:
Name:   exitcode
State:  Z (zombie)
Tgid:   15033
Ngid:   0
Pid:    15033
PPid:   15032
TracerPid:  0
Uid:    9508    9508    9508    9508
Gid:    1240    1240    1240    1240
FDSize: 0
Groups: 297 1240 1360 8714 
Threads:    1
SigQ:   0/71487
SigPnd: 0000000000000000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000000000
SigCgt: 0000000000000000
CapInh: 0000000000000000
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: 0000001fffffffff
CapAmb: 0000000000000000
Seccomp:    0
Cpus_allowed:   ff
Cpus_allowed_list:  0-7
Mems_allowed:   00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000001
Mems_allowed_list:  0
voluntary_ctxt_switches:    3
nonvoluntary_ctxt_switches: 1

PID 15033 exited normally with status = 23 (0x1700)
$ siginfo47 exitcode -s 13
PID: 15057: exitcode -s 13
Parent PID 15056: pausing while PID 15057 runs
Parent PID 15056: unpaused
Stashed information:
  Signal:       17
  si_signo:     17
  si_code:      2
                [CLD_KILLED] Child has terminated abnormally and did not create a core file.
  si_pid:       15057
  si_uid:       9508
  si_addr:      0x252400003AD1
  si_status:    2
  si_value.int: 13
Contents of /proc/15057/stat:
15057 (exitcode) Z 15056 15056 13211 34827 15056 4228108 177 0 0 0 0 0 0 0 20 0 1 0 511350462 0 0 18446744073709551615 0 0 0 0 0 4096 0 0 0 18446744073709551615 0 0 17 5 0 0 0 0 0 0 0 0 0 0 0 0 0

Contents of /proc/15057/status:
Name:   exitcode
State:  Z (zombie)
Tgid:   15057
Ngid:   0
Pid:    15057
PPid:   15056
TracerPid:  0
Uid:    9508    9508    9508    9508
Gid:    1240    1240    1240    1240
FDSize: 0
Groups: 297 1240 1360 8714 
Threads:    1
SigQ:   1/71487
SigPnd: 0000000000001000
ShdPnd: 0000000000000000
SigBlk: 0000000000000000
SigIgn: 0000000000000000
SigCgt: 0000000000000000
CapInh: 0000000000000000
CapPrm: 0000000000000000
CapEff: 0000000000000000
CapBnd: 0000001fffffffff
CapAmb: 0000000000000000
Seccomp:    0
Cpus_allowed:   ff
Cpus_allowed_list:  0-7
Mems_allowed:   00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000000,00000001
Mems_allowed_list:  0
voluntary_ctxt_switches:    2
nonvoluntary_ctxt_switches: 1

PID 15057 died from signal number = 13 (0x000D)
$ exitcode -h
Usage: exitcode [-hV] [-s signal] [exit-status]
  -h         Print this help message and exit
  -s signal  Kill self with signal number
  -V         Print version information and exit

$

正如帮助消息所指出的，exitcode程序以退出状态终止，通常是 ( exitcode 23) 或作为信号 ( exitcode -s 13) 的结果。

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