When building a sample program with /def=_USE_STD_STAT, you can observe the following: o When the DECC$POSIX_STYLE_UID logical is enabled: - For a system, that supports POSIX style identifiers: - getpwnam_r API reads information from the TCP/IP proxy database and fills UID and GID with values from the TCP/IP proxy database. - getgrgid_r API returns gr_name and gr_mem from the right's database associated with GID returned by getpwnam_r API. - System with no support for POSIX style identifiers, getpwnam_r fills GID and UID with SYSGEN parameters as "DEFUID" and "DEFGID". o When the DECC$POSIX_STYLE_UID logical is not defined: getpwnam function returns information about a user database entry for the specified name, which is specified in SYSUAF.DAT #include <unistd> // getuid() #include <pwd> // getpwuid_r() #include <grp> #include <errno.h> #include <stdio.h> #include <string.h> main() { struct passwd pwd2; const unsigned int PWD_BUFF_SIZE = 1024; const unsigned int GRP_BUFF_SIZE = 1024; struct passwd *p_passwd; struct passwd *result; struct group *grpresult; struct group grp; char pwdBuffer[PWD_BUFF_SIZE],*name; char grpBuffer[GRP_BUFF_SIZE]; char buf[PWD_BUFF_SIZE]; gid_t gid; uid_t uid; int status; p_passwd = getpwnam("user1"); uid=p_passwd->pw_uid; gid=p_passwd->pw_gid; printf("User id is %u\n", uid); printf("Group id is %u\n", gid); status = getpwnam_r("user1", &pwd2, pwdBuffer, PWD_BUFF_SIZE, &result); gid = pwd2.pw_gid; status = getgrgid_r(gid, &grp, grpBuffer, GRP_BUFF_SIZE, &grpresult); gid=grp.gr_gid; name=grp.gr_name; strcpy(name,grp.gr_name); printf("Group id is %u\n", gid); printf("Group name is %s\n", name); } Running the example program with /def=_USE_STD_STAT produces the following result: o When the DECC$POSIX_STYLE_UID logical is NOT enabled, prints uid as 11010118 (result of 65536*168+ 70) and gid as 168 with group name as RTL. o When the DECC$POSIX_STYLE_UID logical is enabled and POSIX style identifiers are supported, prints uid as 70, gid as 168 with group name as FOR_POSIX_TEST (retrieved from TCP/IP proxy database). o When the DECC$POSIX_STYLE_UID logical is enabled, but POSIX style identifiers are not supported, prints uid as DEFUID, gid as DEFGID with group name as invalid buffer.