studyProcess.c

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

int main(int argc, char **argv) {
    FILE *fp;
    char buf[BUFSIZ];
    
   system("echo \"OGEHOGE\">test.txt");
    fp = fopen("./test.txt","rb");
    fgets(buf, BUFSIZ,fp);
    printf(buf);
    
   // setenv("HOGEHOGE","abd",1); 
    //putenv("HOGEHOGE=abz");
    printf("HOGEHOGE=%s\n", getenv("HOGEHOGE"));
    
    int pid,status;
    if((pid = fork()) < 0) { // 失敗時は -1 が返る
        perror("fork failed");
        return 1;
    } else if(pid==0){
        putenv("HOGEHOGE=abz");
        printf("son HOGEHOGE=%s\n",getenv("HOGEHOGE"));
    } else {
     waitpid(0, &status,0);
        printf("parent HOGEHOGE=%s\n",getenv("HOGEHOGE"));
        printf("finish!");
    }
 return 0;   
}