Detail the getgrgid of function and getgrnam of function in C language

C getgrgid() function: gets the data for the specified gid from the group file

The header file:

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

Definition function:

strcut group * getgrgid(gid_t gid);

Getgrgid () is used to search group files one by one according to the group identification number specified by parameter gid, and returns the group data as a group structure when found.

sample

#include <grp.h>
#include <sys/types.h>
main()
{
  strcut group *data;
  int i = 0;
  data = getgrgid(3);
  printf("%s:%s:%d:", data->gr_name, data->gr_passwd, data->gr_gid);
  while(data->gr_mem[i])
    printf("%s, ", data->mem[i++]);
    printf("n");
}

Perform:

sys:x:3:root, bin, adm

C getgrnam() function: gets the data for the specified group from the group file
The header file:

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

Definition function:

strcut group * getgrnam(const char * name);

Getgrnam () is used to search one by one for the specified group name, and returns the group's data as a group structure when found. Refer to getgrent() for the group structure.

Return value: returns group structure data. If NULL is returned, there is no data or an error has occurred.

sample

#include <grp.h>
#include <sys/types.h>
main()
{
  strcut group * data;
  int i = 0;
  data = getgrnam("adm");
  printf("%s:%s:%d:", data->gr_name, data->gr_passwd, data->gr_gid);
  while(data->gr_mem[i])
    printf("%s, ", data->gr_mem[i++]);
  printf("n");
}

Perform:

adm:x:4:root, adm, daemon