C语言 错误的文件描述符
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Bad file descriptor
提问by Lucy
I'm learning about file descriptors and I wrote this code:
我正在学习文件描述符，并编写了以下代码：
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
int fdrd, fdwr, fdwt;
char c;
main (int argc, char *argv[]) {
if((fdwt = open("output", O_CREAT, 0777)) == -1) {
perror("Error opening the file:");
exit(1);
}
char c = 'x';
if(write(fdwt, &c, 1) == -1) {
perror("Error writing the file:");
}
close(fdwt);
exit(0);
}
, but I'm getting: Error writing the file:: Bad file descriptor
，但我得到： Error writing the file:: Bad file descriptor
I don't know what could be wrong, since this is a very simple example.
我不知道有什么问题，因为这是一个非常简单的例子。
回答by patapizza
Try this:
尝试这个：
open("output", O_CREAT|O_WRONLY, 0777)
回答by RedX
I think O_CREATalone is not enough. Try adding O_WRONLYas flag to the open command.
我觉得O_CREAT光靠自己是不够的。尝试将O_WRONLYas 标志添加到 open 命令。
回答by spacehunt
According to the open(2) man page:
根据 open(2) 手册页：
The argument flags must include one of the following access modes: O_RDONLY, O_WRONLY, or O_RDWR.
参数标志必须包括以下访问模式之一：O_RDONLY、O_WRONLY 或 O_RDWR。
So yes, as suggested by others, please change your opento open("output", O_CREAT|O_WRONLY, 0777));. Use O_RDWRif you need to read from the file. You may also want O_TRUNC-- see the man page for details.
所以是的，正如其他人所建议的那样，请将您open的open("output", O_CREAT|O_WRONLY, 0777));. O_RDWR如果您需要从文件中读取，请使用。您可能还需要O_TRUNC- 有关详细信息，请参阅手册页。
