eaccess (3) - check effective user's permissions for a file
euidaccess (3) - check effective user's permissions for a file
getegid (3p) - get the effective group ID
geteuid (3p) - get the effective user ID
getresgid (2) - get real, effective and saved user/group IDs
getresgid32 (2) - get real, effective and saved user/group IDs
getresuid (2) - get real, effective and saved user/group IDs
getresuid32 (2) - get real, effective and saved user/group IDs
id (1) - print real and effective user and group IDs
setegid (2) - set effective user or group ID
setegid (3p) - set the effective group ID
seteuid (2) - set effective user or group ID
seteuid (3p) - set effective user ID
setregid (2) - set real and/or effective user or group ID
setregid (3p) - set real and effective group IDs
setregid32 (2) - set real and/or effective user or group ID
setresgid (2) - set real, effective and saved user or group ID
setresgid32 (2) - set real, effective and saved user or group ID
setresuid (2) - set real, effective and saved user or group ID
setresuid32 (2) - set real, effective and saved user or group ID
setreuid (2) - set real and/or effective user or group ID
setreuid (3p) - set real and effective user IDs
setreuid32 (2) - set real and/or effective user or group ID
whoami (1) - print effective userid