c system()函数导致分段错误答案

【问题标题】：c system () function cause a segmentation faultc system()函数导致分段错误
【发布时间】：2016-06-15 09:31:31
【问题描述】：

我使用system 函数在我的使用 openwrt 发行版作为嵌入式操作系统的设备。

int system(const char *command);

我的程序如下所示

int check_file_dir(char *name)
{
    int i = 0;
    char command[128];
    sprintf(command, "ls /etc/config/%s &> /dev/null", name);
    printf("====> command =%s \n", command);
    i = system(command);
    return i;
}

void get_file_info () 
{
char name[128]; 
struct dirent *d_file;
struct stat attr;
char path[128];
char s_now[sizeof "AAAA-MM-JJTHH:MM:SS.000Z"];

   if ((dir = opendir ("/etc/config/")) != NULL) 
   {
        while ((d_file = readdir (dir)) != NULL) 
        {
            if(d_file->d_name[0] == '.')
                continue;
            sprintf(path, "/etc/config/%s", d_file->d_name);
            stat(path, &attr);
            strftime(s_now, sizeof s_now, "%Y-%m-%dT%H:%M:%S.000Z", localtime(&attr.st_mtime));
        }
    }
    closedir (dir);
    int j;
    for (j = 0; j< FILE_NUMBER; j++)
    {
       sprintf(name, "/etc/config/file%d", j); 
       if(check_file_dir(name) !=0)
           printf("file doesn't exist \n");
    }
}


 void main () 
{
get_file_info();
get_file_info();
}

问题是由system 函数导致get_file_info() 被调用两次！

他们有什么预防措施来避免系统段错误？

【问题讨论】：

可能是缓冲区大小不足。尝试给char command[]更多字节。
我已经这样做了，将 buf 大小增加到 512，但是同样的问题
sprintf(path, "/etc/config/", d_file->d_name); 这是什么？
@Sourav 好点！ @Anis_Stack，sprintf() 的第二个参数需要一些 % 修饰符："/etc/config/%s"
发布您的实际代码。 get_name_from_conf("/etc/config", &name) 甚至不会编译。

标签： c

【解决方案1】：

我无法重现您的问题，因为您的代码无法编译。这是您的程序的工作版本，带有更改注释（并用 testdir 替换 /etc/config）：

#include <limits.h> /* for PATH_MAX and LINE_MAX */
#include <stdio.h>  /* header include was missing */
#include <stdlib.h> /* header include was missing */
#include <time.h>   /* header include was missing */

#include <dirent.h>   /* header include was missing */
#include <sys/stat.h> /* header include was missing */

int check_file_dir(char *name)
{
    int i = 0;
    char command[LINE_MAX];  /* standard max command line length */
    /* path was wrong below */
    sprintf(command, "ls %s &> /dev/null", name);
    printf("====> command =%s \n", command);
    i = system(command);
    return i;
}

void get_file_info()
{
    char name[PATH_MAX]; /* standard max path length */
    struct dirent *d_file;
    struct stat attr;
    char path[PATH_MAX]; /* standard max path length */
    char s_now[sizeof "AAAA-MM-JJTHH:MM:SS.000Z"];
    DIR *dir;            /* declaration was missing */
    int FILE_NUMBER = 0; /* declaration was missing */

    if ((dir = opendir("testdir")) == NULL)
        return; /* no point to go on */

    while ((d_file = readdir(dir)) != NULL) {
        if (d_file->d_name[0] == '.')
            continue;
        sprintf(path, "testdir/%s", d_file->d_name);
        stat(path, &attr);
        strftime(s_now, sizeof s_now, "%Y-%m-%dT%H:%M:%S.000Z",
                 localtime(&attr.st_mtime)); /* not used? */
        ++FILE_NUMBER; /* assuming this is what you meant to do */
    }
    closedir(dir); /* was called even if !opendir() */

    int j;
    for (j = 0; j < FILE_NUMBER; j++) {
        sprintf(name, "testdir/file%d", j);
        if (check_file_dir(name) != 0)
            printf("file doesn't exist \n");
    }
}

int main(void) /* int and (void) */
{
    get_file_info();
    get_file_info();
    return 0; /* was missing */
}

【讨论】：

【解决方案2】：

根据这个链接 How do I execute a Shell built-in command with a C function?

使用 execl("sh", "sh", "-c", command, NULL) 代替系统

【讨论】：