Size of pid_t, uid_t, gid_t on Linux
#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)...
On an i686 and x86_64 (so, 32-bit and 64-bit) processor running Linux >= 3.0.0, the answer is:
pid_t: 4uid_t: 4gid_t: 4
On intel architectures, sizes are defined in /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_t
and gid_t
are unsigned 32-bit integers and pid_t
is a signed 32-bit integer. This applies for both 32- and 64-bits.
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.