c_header: system()(linux-stdlib.h)

c_header:  system()(linux-stdlib.h)

 

 

 

 

一、源码

[root@rocky c]# cat  systemcall.c 
/*
 *
 *
 * file_name = systemcall.c
 *
 *
 * 
 */ 


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


#include<unistd.h>      // sleep()
#include<time.h>        // time_t, time()


// <stdlib.h>: system()
void
msg1()
{
   int size = 5;
   char *cmd[] = {"pwd", "ls", "date", "uname -a", "cd ~; ls -l"};

  for(int i=0; i<size; i++)
  {
    printf("\n");
    printf("\n\t== run_cmd_start: [ %s ]\t==\n", cmd[i]);
      system(cmd[i]);
    printf("\t-- run_cmd_end: [ %s ]\t--\n", cmd[i]);
    printf("\n");
  }
}


// <stdlib.h>: system()
void
msg2(int size, char **cmd)
{

  printf("\n");
  printf("\n");
  for(int i=1; i<size; i++)
  {
    printf("[%s]\n", cmd[i]);
      system(cmd[i]);
    printf("\n");
    printf("\n");
  }
  printf("\n");
}


// <stdlib.h>: srand(), rand()
void
msg3()
{
  const int SIZE = 10;
  time_t t;
  int rand_dig = 0;
  printf("\n\trand_max = %d\n\n", RAND_MAX);
  for(int i=1; i<= SIZE; i++)
  {
    printf("\twait[ 2 ] seconds...\n");
    sleep(2);
    srand( (unsigned)time(&t) );
    rand_dig = ( rand()%100 );
    printf("\t\trand_number<rang:0~100>[time_%d] = %d\n", i, rand_dig );
  }
  printf("\n\n");
}


// <stdlib.h>: abort(void); atexit(func); exit(int);
void
callee_by_atexit()
{
  printf("\n\tOS: CALLEE_BY_ATEXIT()\n\n");
}


void
msg4()
{
  // getting random number
  time_t t;
  int rand_range = 0;
  srand(( unsigned)time(&t) );
  // rand_range: 0 ~ 100
  rand_range = rand()%100 ;

  if(rand_range > 90)
  {
    printf("\n\t [rand_range = %d](range_range > 90); run_function[ abort() ]\n\n", rand_range);
    abort();
  }else if( rand_range < 40 )
  {
    printf("\n\t [rand_range = %d](range_range < 40); run_function[ exit(80) ]\n\n", rand_range);
    exit(80);
  }else
  {
    printf("\n\t [rand_range = %d]( 40 <= rand_range <= 90); run_function[ atexit(callee_by_atexit()) ]\n\n", rand_range);
    atexit(callee_by_atexit);
  }
}

// -- sperate line --




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

  // msg1();
  msg2(argc, argv);
  // msg3();
  // msg4();

  return 0;

}
[root@rocky c]# 
[root@rocky c]# 

 

 

 

 

二、运行结果：

 

[root@rocky c]# uname  -a
Linux rocky 5.14.0-162.6.1.el9_1.0.1.x86_64 #1 SMP PREEMPT_DYNAMIC Mon Nov 28 18:44:09 UTC 2022 x86_64 x86_64 x86_64 GNU/Linux
[root@rocky c]# 
[root@rocky c]# 
[root@rocky c]# gcc  --version
gcc (GCC) 11.3.1 20220421 (Red Hat 11.3.1-2)
Copyright (C) 2021 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

[root@rocky c]# 
[root@rocky c]# 
[root@rocky c]# gcc -g -Wall -o systemcall systemcall.c && ./systemcall "ls -l" "pwd" "echo hello, world!"


[ls -l]
total 80
-rw-r--r-- 1 root root   625 Dec 28 03:11 arg_test.c
-rw-r--r-- 1 root root   900 Dec 31 01:04 asm_test.c
-rw-r--r-- 1 root root   539 Dec 29 01:25 char_test.c
-rw-r--r-- 1 root root    41 Jan 20 00:50 me.txt
-rw-r--r-- 1 root root  2352 Dec 28 23:56 pointer_array.c
-rw-r--r-- 1 root root   490 Dec 29 17:09 preprocessor.c
-rw-r--r-- 1 root root  2027 Jan 20 00:51 stdio_header.c
-rw-r--r-- 1 root root  1967 Jan 14 19:02 stdlib_header.c
-rwxr-xr-x 1 root root 32320 Jan 20 03:12 systemcall
-rw-r--r-- 1 root root  2035 Jan 20 03:08 systemcall.c
-rw-r--r-- 1 root root   154 Jan  4 21:08 template.c
-rw-r--r-- 1 root root   536 Dec 29 18:34 thread_test.c
-rw-r--r-- 1 root root  1166 Jan  4 23:38 time_header.c


[pwd]
/root/user/lidawei/tmp/c


[echo hello, world!]
hello, world!



[root@rocky c]# 
[root@rocky c]#