getgroups(2) [osx man page]

GETGROUPS(2)						      BSD System Calls Manual						      GETGROUPS(2)

NAME

     getgroups -- get group access list

SYNOPSIS

     #include <unistd.h>

     int
     getgroups(int gidsetsize, gid_t grouplist[]);

DESCRIPTION

     getgroups() gets the current group access list of the current user process and stores it in the array grouplist[].  The parameter gidsetsize
     indicates the number of entries that may be placed in grouplist[].  getgroups() returns the actual number of groups returned in grouplist[].
     However, no more than {NGROUPS_MAX} will be returned. If gidsetsize is 0, getgroups() returns the number of groups without modifying the
     grouplist[] array.

     Calling initgroups(3) to opt-in for supplementary groups will cause getgroups() to return a single entry, the GID that was passed to
     initgroups(3).

     To provide compatibility with applications that use getgroups() in environments where users may be in more than {NGROUPS_MAX} groups, a vari-
     ant of getgroups(), obtained when compiling with either the macros _DARWIN_UNLIMITED_GETGROUPS or _DARWIN_C_SOURCE defined, can be used that
     is not limited to {NGROUPS_MAX} groups.  However, this variant only returns the user's default group access list and not the group list modi-
     fied by a call to setgroups(2) (either in the current process or an ancestor process).  Use of setgroups(2) is highly discouraged, and there
     is no foolproof way to determine if it has been previously called.

RETURN VALUES

     A successful call returns the number of groups in the group set.  Otherwise, a value of -1 is returned and the global integer variable errno
     is set to indicate the error.

ERRORS

     The possible errors for getgroups() are:

     [EFAULT]		The argument grouplist specifies an invalid address.

     [EINVAL]		The argument gidsetsize, although non-zero, is smaller than the number of groups in the group set.

LEGACY SYNOPSIS

     #include <sys/param.h>
     #include <sys/types.h>
     #include <unistd.h>

     The include files <sys/param.h> and <sys/types.h> are necessary.

SEE ALSO

     setgroups(2), initgroups(3), compat(5)

HISTORY

     The getgroups() function call appeared in 4.2BSD.

4.2 Berkeley Distribution					 October 28, 2011					 4.2 Berkeley Distribution

getgroups(2)							System Calls Manual						      getgroups(2)

NAME

       getgroups - Gets the supplementary group IDs of the current process

SYNOPSIS

       #include <unistd.h>

       int getgroups(
	       int gidsetsize,
	       gid_t grouplist[]);

       Application  developers	may  want  to  specify an #include statement for <sys/types.h> before the one for <unistd.h> if programs are being
       developed for multiple platforms. The additional #include statement is not required on Tru64 UNIX systems or by ISO  or	X/Open	standards,
       but may be required on other vendors' systems that conform to these standards.

STANDARDS

       Interfaces documented on this reference page conform to industry standards as follows:

       getgroups(): XSH4.2

       Refer to the standards(5) reference page for more information about industry standards and associated tags.

PARAMETERS

       Indicates  the  number  of entries that can be stored in the array pointed to by the grouplist parameter.  Points to the array in which the
       process' supplementary group IDs are stored.  Element grouplist[0] is the effective group ID of the process.

DESCRIPTION

       The getgroups() function gets the current supplementary group IDs of the calling process.  The list is stored in the array  pointed  to	by
       the grouplist parameter.  The gidsetsize parameter indicates the number of entries that can be stored in this array.

       The  getgroups() function never returns more than NGROUPS_MAX entries. (NGROUPS_MAX is a constant defined in the limits.h header file.)	If
       the gidsetsize parameter is 0 (zero), the getgroups() function returns the number of supplementary group IDs associated	with  the  calling
       process without modifying the array pointed to by grouplist.

RETURN VALUES

       Upon successful completion, the getgroups() function returns the number of elements stored in the array pointed to by the grouplist parame-
       ter. Otherwise, the function returns a value of -1 and sets errno to indicate the error.

ERRORS

       If the getgroups() function fails, errno might be set to one of the following values: [Tru64 UNIX]  The gidsetsize and grouplist parameters
       specify	an  array  that  is  partially	or  completely outside of the allocated address space of the process.  The gidsetsize parameter is
       nonzero and smaller than the number of supplementary group IDs.

RELATED INFORMATION

       Commands: groups(1)

       Functions: setgroups(2), getgid(2), setsid(2), initgroups(3)

       Standards: standards(5) delim off

																      getgroups(2)