是否有可能使用带O_APPEND模式打开写（）的文件？ [英] Is it possible to use write() in file opened with O_APPEND mode?

问题描述

#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>

int main(){
    FILE * fp;
    char buf[128];
    int fd = open("/home/pdave/Downloads/ccode/fileout1",O_CREAT);
    printf("fd after creat:%d",fd);
    close(fd);
    fd = open("/home/pdave/Downloads/ccode/fileout1",O_APPEND);
    printf("fd after append:%d",fd);
    int more=1;
    int ret=0;
    while(more){
        puts("enter text:");
        scanf("%s",buf);
        puts(buf);
        ret=write(fd,buf,128);
        printf("ret:%d",ret);
        puts("more?");
        scanf("%d",&more);
    }
}

以上尝试写字符在 O_APPEND 模式open函数打开的文件。它的工作原理，当它打开与 O_WRONLY 模式，而不是在它的 O_APPEND 打开。我怎样才能追加到它不与W打开，然后用求 SEEK_END 然后的fputs 来的文件或者类似的东西？

The above tries to write characters to a file opened with the open function in O_APPEND mode. It works when it is opened with O_WRONLY mode but not when it is opened in O_APPEND. How can I append to it without opening with "w" and then using seek to SEEK_END and then fputs to the file or something like that?

推荐答案

使用 O_WRONLY | O_APPEND ，你仍然需要的文件访问模式。 （对于某些[最？]编译器，不包括文件访问标志将导致文件被视为只读的，如果没有的话你有一个 EINVAL 错误。）

Use O_WRONLY | O_APPEND, you still need the file access mode. (For some [most?] compilers, not including a file access flag will cause the file to be treated as read-only, and if not then you'd have an EINVAL error.)

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