getgrgid_r()--Get Group Information Using Group ID

 #include <sys/types.h>
 #include <grp.h>

 int getgrgid_r(gid_t gid, struct group *grp,  
 char *buffer, size_t bufsize, struct group
 **result);  

The getgrgid_r() function updates the group structure pointed to by grp and stores a pointer to that structure in the location pointed to by result. The structure contains an entry from the user database with a matching GID.

Parameters

gid

(Input) Group ID.

grp

(Input) A pointer to a group structure.

buffer

(Input) A pointer to a buffer from which memory is allocated to hold storage areas referenced by the group structure grp.

bufsize

(Input) The size of buffer in bytes.

result

(Input) A pointer to a location in which a pointer to the updated group structure is stored. If an error occurs or if the requested entry cannot be found, a NULL pointer is stored in this location.

The struct group, which is defined in the grp.h header file, has the following elements:

Authorities

*READ authority is required to the user profile associated with the gid. If the user does not have *READ authority, only the name of the group and the group ID values are returned.

Return Value

0

getgrgid_r was successful.

Any other value

Failure: The return value contains an error number indicating the error.

Error Conditions

If getgrgid_r() is not successful, the return value usually indicates one of the following errors. Under some conditions, the value could indicate an error other than those listed here.

Related Information

• The <grp.h> file Header Files for UNIX-Type Functions(see )
  
• getgrgid()--Get Group Information Using Group ID

Example

See Code disclaimer information for information pertaining to code examples.

The following example gets the group information for the gid of 91. The group name is GROUP1. There are two group members, CLIFF and PATRICK.

#include <sys/types.h>
#include <grp.h>
#include <stdio.h>
#include <errno.h>

main()
{ short int lp;
  struct group grp;
  struct group * grpptr=&grp;
  struct group * tempGrpPtr;
  char grpbuffer[200];
  int  grplinelen = sizeof(grpbuffer);

  if ((getgrgid_r(91,grpptr,grpbuffer,grplinelen,&tempGrpPtr))!=0)
     perror("getgrgid_r() error.");
  else
  {
     printf("\nThe group name is: %s\n", grp.gr_name);
     printf("The gid        is: %u\n", grp.gr_gid);
     for (lp = 1; NULL != *(grp.gr_mem); lp++, (grp.gr_mem)++)
        printf("Group Member %d is: %s\n", lp, *(grp.gr_mem));
  }

}

Output:

  The group name is: GROUP1
  The gid        is: 91
  Group member 1 is: CLIFF
  Group member 2 is: PATRICK