文件描述符的可能值是什么? [英] What are the possible values for file descriptors?
问题描述
我有兴趣知道文件描述符可以使用的有效值.
I am interested to know the valid values which I can expect for a file descriptor.
请让我解释一下.我知道，例如，当我在Linux系统上使用#include <unistd.h>时，将调用一个打开文件进行读取的请求:
Please let me explain a bit. I know that, for instance, when I use #include <unistd.h> on my linux system then a call to open a file for reading:
int fileDescriptor;
fileDescriptor = open("/some/filename",O_RDONLY);
可能会发生错误，结果我收到-1.
偶然地，(-1)否定词必须具有特殊的含义.是否所有其他值都是有效的文件描述符?也就是负数，例如-2和-1023?
an error might occur and I receive -1 as a result.
Incidently the (-1) negative one must have somewhat of a special meaning. Is it that all other values are valid file descriptors? i.e. also negative ones like -2 and -1023?
假设int是4个字节(sizeof(int)==4)，那么
Assuming that int is 4 bytes (sizeof(int)==4), then would
(-1) = 10000000 0000000 00000000 00000001
将是唯一可检测到的无效文件描述符吗? 其他人会喜欢吗?
would be the only detectable invalid file descriptor? Would others like:
-
(0) = 00000000 0000000 00000000 00000000 -
(-2) = 10000000 0000000 00000000 00000010 -
(2) = 00000000 0000000 00000000 00000010
(0) = 00000000 0000000 00000000 00000000(-2) = 10000000 0000000 00000000 00000010(2) = 00000000 0000000 00000000 00000010
还好吗? 由于文件描述符可以存储4个字节，因此我最多可以有 (2 ^(8 * 4)-1)个有效的文件描述符，因此这将是我可以打开的最大文件数量，对吗?
be ok? Since the file descriptor could store 4 bytes I could have therefore a maximum of (2^(8*4)-1) valid file descriptors and consequently this would be the maximum number of files I can have open, correct?
再次说明:
我应该期望一个(有效的)文件描述符是什么?
除-1以外的任何值?
推荐答案
来自手册页:
open()返回文件描述符，一个小的非负整数.
open()returns a file descriptor, a small, nonnegative integer.
然后:
open()和creat()返回新的文件描述符，；如果发生错误，则返回-1.
open()andcreat()return the new file descriptor, or -1 if an error occurred
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