擷取system系統調用的輸出

#include <stdlib.h>#include <string.h>#include <stdio.h>#include <fcntl.h>#include <unistd.h>static int getResultFromSystemCall(const char* pCmd, char* pResult, int size){   int fd[2];   if(pipe(fd))   {      printf("pipe error!\n");      return -1;   }   //hide stdout   int bak_fd = dup(STDOUT_FILENO);   int new_fd = dup2(fd[1], STDOUT_FILENO);   //the output of `pCmd` is write into fd[1]   system(pCmd);   read(fd[0], pResult, size-1);   pResult[strlen(pResult)-1] = 0;   //resume stdout   dup2(bak_fd, new_fd);   return 0;}int main(void){   char* filePath = "./test.conf";   char* key = "aaa";   char res[100] = {0};   char cmd[100] = {0};   sprintf(cmd, "cat %s | grep -m 1 -E \"^%s\" | cut -d= -f2 | sed 's/[[:space:]]*//g'", filePath, key);    getResultFromSystemCall(cmd, res, sizeof(res)/sizeof(res[0]));   //getResultFromSystemCall("export aaa=1234 && echo ${aaa#=}", res, sizeof(res)/sizeof(res[0]));   printf("result is [%s]\n", res);   return 0;}