getuid(2)

1getuid(2)                     System Calls Manual                    getuid(2)
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NAME

6       getuid, geteuid - get user identity
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LIBRARY

9       Standard C library (libc, -lc)
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SYNOPSIS

12       #include <unistd.h>
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14       uid_t getuid(void);
15       uid_t geteuid(void);
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DESCRIPTION

18       getuid() returns the real user ID of the calling process.
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20       geteuid() returns the effective user ID of the calling process.
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ERRORS

23       These functions are always successful and never modify errno.
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STANDARDS

26       POSIX.1-2008.
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HISTORY

29       POSIX.1-2001, 4.3BSD.
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31       In  UNIX V6  the getuid() call returned (euid << 8) + uid.  UNIX V7 in‐
32       troduced separate calls getuid() and geteuid().
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34       The original Linux getuid() and geteuid() system calls  supported  only
35       16-bit  user  IDs.   Subsequently,  Linux  2.4 added getuid32() and ge‐
36       teuid32(), supporting 32-bit IDs.  The  glibc  getuid()  and  geteuid()
37       wrapper  functions transparently deal with the variations across kernel
38       versions.
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40       On Alpha, instead of a pair of getuid() and geteuid() system  calls,  a
41       single  getxuid() system call is provided, which returns a pair of real
42       and effective UIDs.  The glibc getuid() and geteuid() wrapper functions
43       transparently  deal  with  this.   See syscall(2) for details regarding
44       register mapping.
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