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getgroups (3)
  • getgroups (2) ( Solaris man: Системные вызовы )
  • getgroups (2) ( FreeBSD man: Системные вызовы )
  • getgroups (2) ( Русские man: Системные вызовы )
  • getgroups (2) ( Linux man: Системные вызовы )
  • >> getgroups (3) ( POSIX man: Библиотечные вызовы )
  •  

    NAME

    getgroups - get supplementary group IDs
     
    

    SYNOPSIS

    #include <unistd.h>

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

    DESCRIPTION

    The getgroups() function shall fill in the array grouplist with the current supplementary group IDs of the calling process. It is implementation-defined whether getgroups() also returns the effective group ID in the grouplist array.

    The gidsetsize argument specifies the number of elements in the array grouplist. The actual number of group IDs stored in the array shall be returned. The values of array entries with indices greater than or equal to the value returned are undefined.

    If gidsetsize is 0, getgroups() shall return the number of group IDs that it would otherwise return without modifying the array pointed to by grouplist.

    If the effective group ID of the process is returned with the supplementary group IDs, the value returned shall always be greater than or equal to one and less than or equal to the value of {NGROUPS_MAX}+1.  

    RETURN VALUE

    Upon successful completion, the number of supplementary group IDs shall be returned. A return value of -1 indicates failure and errno shall be set to indicate the error.  

    ERRORS

    The getgroups() function shall fail if:

    EINVAL
    The gidsetsize argument is non-zero and less than the number of group IDs that would have been returned.

    The following sections are informative.  

    EXAMPLES

     

    Getting the Supplementary Group IDs of the Calling Process

    The following example places the current supplementary group IDs of the calling process into the group array.

    
    #include <sys/types.h>
    #include <unistd.h>
    ...
    gid_t *group;
    int nogroups;
    long ngroups_max;
    
    
    ngroups_max = sysconf(_SC_NGROUPS_MAX) + 1;
    group = (gid_t *)malloc(ngroups_max *sizeof(gid_t));
    
    
    ngroups = getgroups(ngroups_max, group);
    
    
     

    APPLICATION USAGE

    None.  

    RATIONALE

    The related function setgroups() is a privileged operation and therefore is not covered by this volume of IEEE Std 1003.1-2001.

    As implied by the definition of supplementary groups, the effective group ID may appear in the array returned by getgroups() or it may be returned only by getegid(). Duplication may exist, but the application needs to call getegid() to be sure of getting all of the information. Various implementation variations and administrative sequences cause the set of groups appearing in the result of getgroups() to vary in order and as to whether the effective group ID is included, even when the set of groups is the same (in the mathematical sense of "set"). (The history of a process and its parents could affect the details of the result.)

    Application writers should note that {NGROUPS_MAX} is not necessarily a constant on all implementations.  

    FUTURE DIRECTIONS

    None.  

    SEE ALSO

    getegid() , setgid() , the Base Definitions volume of IEEE Std 1003.1-2001, <sys/types.h>, <unistd.h>  

    COPYRIGHT

    Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics Engineers, Inc and The Open Group. In the event of any discrepancy between this version and the original IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee document. The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .


     

    Index

    NAME
    SYNOPSIS
    DESCRIPTION
    RETURN VALUE
    ERRORS
    EXAMPLES
    Getting the Supplementary Group IDs of the Calling Process
    APPLICATION USAGE
    RATIONALE
    FUTURE DIRECTIONS
    SEE ALSO
    COPYRIGHT


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