Table of contents
open
View the open function
man 2 open
in
#include <unistd.h>Include
#include <sys/types.h>
#include <sys/stat.h>parameter pathname
The path and file name of the open file.
parameter flags
Two types of parameters can be selected for transmission, namely the main class and the subclass. The primary and secondary parameters can be used together.
main class
Only one is allowed, not both.
O_RDONLY : Open as read-only.
O_WRONLY : Open for writing only.
O_RDWR : Open in readable and writable mode.
Subclass
Can be used in multiple combinations.
O_CREAT : Create the file if it does not exist.
O_EXCL : Returns an error message if the O_CREAT option is used and the file exists.
O_NOCTTY : If the file is a terminal, then the terminal cannot call the controlling terminal of the process of the open system call.
O_TRUNC : If the file already exists, delete the original data in the file.
O_APPEND : Open in append mode.
parameter mode
If the file is created, specify its permissions as mode. mode is an octal permission code.
return value
Success : Open the file to get the corresponding file descriptor and integer data.
Failed : -1, set eerno.
close
View the close function
man 2 close
parameter fp
The corresponding file descriptor obtained by opening the file.
test code
#include <unistd.h>
#include <fcntl.h> //为flags参数服务
#include <stdio.h>
int main(){
int fp,close_num;
fp=open("./aaa.txt",O_RDWR|O_CREAT,0644); //以读写的方式打开，如果该文件不存在则创建，创建的权限为644
printf("fp=%d\n",fp);
close_num=close(fp);
printf("cloase_num:%d\n",close_num);
return 0;
}Test Results
error handling function
#incldue <errno.h>
printf("error:%s\n",strerror(errno));perror("xxx error")