creat函数和open函数的区别

顾名思义，creat创建新文件，open打开文件。但，open也可以起到创建新文件的作用。

#include <fcntl.h>
int creat(const char *pathname, mode_t mode);
//Returns: file descriptor opened for write-only if OK, 1 on error

当creat的文件已存在时，creat将截断文件原文件，文件的修改时间访问时间也一并被修改。

creat相当于：open (pathname, O_WRONLY | O_CREAT | O_TRUNC, mode);

open

A file is opened or created by calling the open function.

#include <fcntl.h>
int open(const char *pathname, int oflag, ... /*mode_t mode   */ );
//Returns: file descriptor if OK, 1 on error

第三个参数只有在创建文件时才有用。

One deficiency with creat is that the file is opened only for writing. Before the new version of open was provided, if we were creating a temporary file that we wanted to write and then read back, we had to call creat, close, and then open. A better way is to use the open function, as in
    open (pathname, O_RDWR | O_CREAT | O_TRUNC, mode);

from APUE

总的来说，open功能更强，包含了creat的功能。建议用open。