File manipulation experiment

File manipulation experiment

Experimental objectives:

1. Master the use of Linux file manipulation functions

Experimental environment and working conditions:
Red Head Linux5.0 or above operating system

Experimental content:

1. Design a program that requires the file "pass" to be opened. If there is no such file, create a new file with permissions set to read only by the owner.

#include<unistd.h>
#include<stdlib.h>
#include<stdio.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<fcntl.h>
int main()
{
 int fd;
 if((fd=open("pass",O_CREAT))<0)
 {
  printf("not exist\n");
 }
 printf("create file pass,it is:%d\n",fd);
 chmod("pass",S_IRUSR|S_IWUSR);
 return 0;
}

2. Design a program that requires creating a new file "hello" and using the write function to write the "Linux software design" string to the file (if you write with the fwrite function, what should you do)

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
int  main()
{
 int fd,twrite;
 if((fd=open("./hello",O_CREAT|O_TRUNC|O_WRONLY,0777))<0)
 {
  printf("open file error");
  exit(1);
 }
 char str[]="the design of C software under Linux";
 if((twrite=write(fd,str,sizeof(str)))<0)
 {
  printf("write file error");
  exit(1);
 }
 close(fd);
 return 0;
}

3. Design a program that requires the read function to read the system file "/ etc / passwd" and display the output in the terminal.

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
int main()
{
 int fd,rtype,wtype;
 char str[30];
 if((fd=open("/etc/passwd",O_RDONLY))<0)
 {
  printf("read file error！");
  exit(1);
 }
 while((rtype=read(fd,str,30))>0)
 {
  if((wtype=write(STDOUT_FILENO,str,rtype))<0)
   printf("write file error");
 }
 close(fd);
      return 0;
}

4. Design a program that requires opening the file "pass". If there is no such file, create a new file; read the system file "/ etc / passwd" and write the contents of the file into the "pass" file.

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <stdlib.h>
int main()
{
 int fdsrc,fddes,nbytes,wtype;
 char str[30];
 if((fddes=open("pass",O_CREAT|O_TRUNC|O_WRONLY,0600))<0)
 {
  printf("open file pass error");
  exit(1);
 }
 if((fdsrc=open("/etc/passwd",O_RDONLY))<0)
 {
  printf("open file error");
  exit(1);
 }
 while((nbytes=read(fdsrc,str,30))>0)
 {
  if((wtype=write(fddes,str,30))<0)
  printf("write file error");
 }
        close(fdsrc);
 close(fddes);
}
 

5. Design a program that requires 10 to be output in decimal, octal, and hexadecimal respectively (here I use the sprintf function).

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include<string.h>
int main()
{
 int x=10;
 char FX[20],PX[20],HX[20];
 sprintf(FX,"%x",x);
 sprintf(PX,"%o",x);
 sprintf(HX,"%d",x);
        write(1,PX,strlen(PX));
  printf("\n");
        write(1,FX,strlen(FX));
  printf("\n");
        write(1,HX,strlen(HX));
        printf("\n");
 return 0;
 
}

6. Design a program that requires the creation of a new directory, with the default permissions of dr–r--r–.

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
int main()
{
 system("mkdir exercise");
 chmod("exercise",0444);
 return 0;
}

7. Design a program that requires the command ls -l> list to create a file, then create a soft link "ls1" and a hard link "ls2", and view the two linked files and the list file.

#include<unistd.h>
#include<stdlib.h>
 
int main()
{
    system("ls -l > list");//>输出重定向，将当前目录下的内容输入到list中
    symlink("list","l1");
    link("list","l2");
    system("ls list -l");
    system("ls l1 -l");
    system("ls l2 -l");
    return 0;
}