Linux 上 pid_t、uid_t、gid_t 的大小
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Size of pid_t, uid_t, gid_t on Linux
提问by Joe Shaw
On Linux systems (either 32- or 64-bit), what is the size of pid_t, uid_t, and gid_t?
在 Linux 系统（32 位或 64 位）上pid_t，uid_t、 和的大小是gid_t多少？
采纳答案by Dave
#include <stdio.h>
#include <sys/types.h>
int main()
{
printf("pid_t: %zu\n", sizeof(pid_t));
printf("uid_t: %zu\n", sizeof(uid_t));
printf("gid_t: %zu\n", sizeof(gid_t));
}
EDIT:Per popular request (and because, realistically, 99% of the people coming to this question are going to be running x86 or x86_64)...
编辑：每个流行的请求（因为，实际上，99% 的人来这个问题将运行 x86 或 x86_64）...
On an i686 and x86_64 (so, 32-bit and 64-bit) processor running Linux >= 3.0.0, the answer is:
在运行 Linux >= 3.0.0 的 i686 和 x86_64（因此，32 位和 64 位）处理器上，答案是：
pid_t: 4
uid_t: 4
gid_t: 4
回答by Joe Shaw
On intel architectures, sizes are defined in /usr/include/bits/typesizes.h:
在英特尔架构上，大小定义为/usr/include/bits/typesizes.h：
#define __UID_T_TYPE __U32_TYPE
#define __GID_T_TYPE __U32_TYPE
#define __PID_T_TYPE __S32_TYPE
In other words, uid_tand gid_tare unsigned 32-bit integers and pid_tis a signed 32-bit integer. This applies for both 32- and 64-bits.
换句话说，uid_t和gid_t是无符号 32 位整数并且pid_t是有符号 32 位整数。这适用于 32 位和 64 位。
I am not sure what they are on other architectures offhand as I don't have any available at the moment, but the definitive way is to compile a program which prints the output of sizeof(uid_t), etc.
我不确定它们在其他架构上是什么，因为我目前没有可用的，但最终的方法是编译一个程序，打印输出sizeof(uid_t)等。
