linux c fork简单调用bin or shell script demo

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// exec shell script

#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
void hello()
{
printf("hello word \n");
}

int main()
{
pid_t pid;
pid=fork();

if(pid<0)
{
printf("fail to fork \n");
exit(3);
}
else if(pid ==0)
{

// child process run testcallexecl
//if(execl("/opt/test/testcallexecl","interp","arg1",NULL)<0)

   // exec shell script /usr/bin/hello    must be set  x privilege to hello
    if(execl("/usr/bin/hello","xx","uu",NULL))
    {
       printf("fail to execl \n");
       exit(2);
    }
    printf("the child is not hello \n");
    exit(0);
}
printf("the parent %u\n",getpid());
return 0;
}

cat /usr/bin/hello

#!/bin/sh

echo hello word

---------------------------------------------------------------------------------------------------

// call bin

#include<stdio.h>
#include<unistd.h>
#include<stdlib.h>
int main()
{
pid_t pid;
pid=fork();

if(pid<0)
{
printf("fail to fork \n");
exit(3);
}
else if(pid ==0)
{

    //exec testpid exec bin file
    if(execvp("testpid",NULL)<0)
    {

       //child process exec
       printf("fail to exec \n");
       exit(2);
    }
    printf("the child is not exec \n");
    exit(0);
}
printf("the parent %u\n",getpid());
return 0;
}

cat pid.c
#include<stdio.h>
#include<unistd.h>

int main()

{
pid_t pid,ppid,uid,euid,gid,egid;

pid=getpid();
ppid=getppid();

uid=getuid();
euid=geteuid();

gid=getgid();
egid = getegid();

printf("id of current process :%u \n",pid);
printf("parent id of current process :%u \n",ppid);
printf("user id of current process :%u \n",uid);
printf("effective user id of current process :%u \n",euid);
printf("gid of current process :%u \n",gid);
printf("effective gid of current process :%u\n",egid);

// setx pid set gid
if(setuid(501)==-1)
   {
     perror("fail to set uid");
     exit(1);
   }
uid=getuid();
euid=geteuid();
printf("id of current process :%u \n",pid);
printf("parent id of current process :%u \n",ppid);
return 0;
}

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