运行脚本，获取其输出并从 c 程序打印

Question

我正在开发一个程序，该程序从脚本获取输出，存储它并以某种方式打印输出，更具体地说是：（名字，中间名/姓氏，键）或（中间名/姓氏，第一名称，密钥）等...

所以我编写了程序，但是当我尝试运行它时，我不断收到分段失败。 编译很好，脚本可以工作，因为我测试过。

有什么可以做的不同或改进的建议吗？

代码：

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>



struct memberinfo  {
char firstname[250]; // all names except last name
char surname [100]; // surname
int  pub_key;         // 0 if the user does not have a key
};

typedef struct memberinfo acc_t;
int counter = 0;

void les_data   (acc_t *classlist);
void skriv_data (acc_t *classlist, char * select);

int main(int argc, char *argv[]) {

     acc_t classlist[200];
     char *ch = NULL;

     if(argc == 2){//checking for additional argument on execute
     ch = argv[1];//pointer becomes main argument
     }
     else if(argc < 2){//if there is less then 2 arguments
     ch = getenv("V1");//pointer gets the default environmental variable.
     }
     else{//same as above, this just makes sure that "ch" don't return with NULL value
     argc == 1;
     ch = getenv("V1");
     }

     read_data  (classlist);//calling the method for executing the script and store output
     print_data(classlist, ch);//calling the method for printing the data

     return 0;
 }


 void read_data(acc_t *classlist) {

    FILE * list;
    char *name, *fname, *lname, *tmp;
    char usertmp[1000], buffer[BUFSIZ+1];//usertmp = temporary list, buffer contain the scripts output     
    int cnt, i, chars_read;

    memset(buffer, '\0', sizeof(buffer));//memsetting buffer with all 0

    list = popen("./classlist.sh", "r");//opening and running the script in a read mode

    while(list!=NULL){ //if list is not NULL, we begin to read from it

        chars_read = fread(buffer, sizeof(char), BUFSIZ, list);//reading from scripts output,
                                                                   //storing in buffer.

        while(chars_read >0){
             //while there are still characters in file we do:



                tmp = buffer;//setting pointer to the text stored in buffer
                for(i = 0; tmp[i]!= '\n'; i++){//for-loop running until a new line is detected        
                    if(tmp[i]== ' '){ //if there is a space in text the counter increases
                            cnt++;
                    }//if end
                }//for-loop end
            name = strtok(buffer,": ");//the complete name is taken from the text in buffer        
            strcpy(usertmp, name);//the name is copied to usertmp array

            for(i = 0; i <(cnt-2); i++){//for-loop

                name = strtok(NULL, ": ");
                strcat(strcat(usertmp, " "), name); //nested strcat??
            }//for-loop end                            // saves the whole name in usertmp[]       


            name = NULL;//setting name to null, clearing the memmory
            strcpy(classlist[counter].firstname, name);//copying first name in array     

            name = strtok(NULL, ": ");//setting to NULL to skip first name
            strcpy(classlist[counter].surname, usertmp);//copy middle/last name

            name = strtok(NULL, ": ");//setting to null to skipp the middle/last name      
            classlist[counter].pub_key = atoi(name);//copy the int key to array

            counter ++;

        }//if(chars_read) end
        pclose(list);
    }//while end


}//read_data end



void print_data (acc_t *classlist, char *select) {

   switch (select[0])
   {
      case 'k':
      printf("%s %s %d\n", classlist[counter].firstname, classlist[counter].surname, 
      classlist[counter].pub_key);
       //printf("Printing out class data:\n");
         break;

      default:
      break;
    }
 }

所以脚本会像这样打印一组成员：

脚本：

#! /bin/bash
grep da2001-2020 /etc/group |cut -f4 -d: > group.txt  
#Getting a list of members

tr -s ',' '\n' < group.txt |sort -k 1 -t',' -n > snm.txt 
#putting numbers in a order

sed 's/^.//' snm.txt > cnm.txt
#removing "s" in front of student number.

rm group.txt #delting group file


cut -f1,5 -d: /etc/passwd |cut -f1 -d, |sort -u > big_list.txt 
 #extracting names from file   
  
grep -f snm.txt big_list.txt   > final.txt  
#comparing the two lists

wc -l < final.txt > amount.txt
 #counting students

for id in $(cat cnm.txt); 
#scaning student numbers that were selected
do

File=$(curl -k --silent -q https://website.com/~$id/pub_key.asc| grep -o 
"BEGIN PGP PUBLIC KEY BLOCK")                                                                                                      
 #curling a request for file indicator pub_key.asc

 if [ "$File" ];
    then
            grep "$id" final.txt | cut -f2 -d: | sort > verification.txt 
             echo -e "$(cat verification.txt): 1 " #indicating has key
            #placing the students who have a key in a file with indicator
   else
          grep "$id" final.txt | cut -f2 -d: | sort > verification.txt 
            echo -e "$(cat verification.txt): 0 " #indicator no key
            #placing the students who dont have key in a file with indicator
     fi



  done 2>&1 | tee classlist.txt #exit loop, print and save output file


  rm amount.txt
  rm cnm.txt 
  rm big_list.txt
  rm snm.txt
  rm verification.txt
  rm final.txt

Answer 1

我可以帮助你了解如何调试这种东西，

当你运行程序时，你会得到这样的分段错误，对吧？

Segmentation fault (core dumped)

这些调试起来很棘手，因为它没有给你太多的工作空间。 但是您应该在可执行文件所在的文件夹中留下一个名为 core 的文件。

核心文件对于跟踪分段错误非常有用，其他人已经解释了如何使用它比我更好：Core dump file analysis

---

如果您按照所有这些步骤操作，您应该能够找到导致崩溃的程序行：

#1  0x0000000000400ab9 in read_data (classlist=0x7ffd308e82a0) at test.c:82
82              strcpy(classlist[counter].firstname, name);//copying first name in array    

从那里，你知道这条线导致了崩溃。

从那里开始，strcpy 的使用存在问题。它导致了崩溃，因为name 设置为NULL，而strcpy 期望它的参数指向一个缓冲区，而NULL 也不是。