Originální popis anglicky: getgrnam, getgrnam_r, getgrgid, getgrgid_r - get group file entry

Návod, kniha: Linux Programmer's Manual

STRUČNĚ

#include <sys/types.h>
#include <grp.h>
 
struct group *getgrnam(const char *name);
 
struct group *getgrgid(gid_t gid);
 
int getgrnam_r(const char *name, struct group *gbuf,
 
          char *buf, size_t buflen, struct group **gbufp);
 
int getgrgid_r(gid_t gid, struct group *gbuf,
 
          char *buf, size_t buflen, struct group **gbufp);

POPIS / INSTRUKCE

The getgrnam() function returns a pointer to a structure containing the group information from /etc/group for the entry that matches the group name name.

The getgrgid() function returns a pointer to a structure containing the group information from /etc/group for the entry that matches the group gid gid.

The getgrnam_r() and getgrgid_r() functions find the same information, but store the retrieved group structure in the space pointed to by gbuf. This group structure contains pointers to strings, and these strings are stored in the buffer buf of size buflen. A pointer to the result (in case of success) or NULL (in case no entry was found or an error occurred) is stored in *gbufp.

The group structure is defined in <grp.h> as follows:

struct group {
      char    *gr_name;      /* group name */
      char    *gr_passwd;    /* group password */
      gid_t   gr_gid;        /* group id */
      char    **gr_mem;      /* group members */
};

The maximum needed size for buf can be found using sysconf(3) with the _SC_GETGR_R_SIZE_MAX parameter.

NÁVRATOVÁ HODNOTA

The getgrnam() and getgrgid() functions return a pointer to the group information structure, or NULL if the matching entry is not found or an error occurs. If an error occurs, errno is set appropriately. If one wants to check errno after the call, it should be set to zero before the call.

The return value may point to static area, and may be overwritten by subsequent calls to getgrent(), getgrgid(), or getgrnam().

The getgrnam_r() and getgrgid_r() functions return zero on success. In case of error, an error value is returned.

CHYBY / ERRORY

0 or ENOENT or ESRCH or EBADF or EPERM or ...: The given name or gid was not found.

EINTR: A signal was caught.

EIO: I/O error.

EMFILE: The maximum number (OPEN_MAX) of files was open already in the calling process.

ENFILE: The maximum number of files was open already in the system.

ENOMEM: Insufficient memory.

ERANGE: Insufficient buffer space supplied.

FILES

/etc/group: group database file

ODPOVÍDAJÍCÍ

SVID 3, BSD 4.3, POSIX 1003.1-2003

NOTES

The formulation given above under "RETURN VALUE" is from POSIX 1003.1-2001. It does not call "not found" an error, hence does not specify what value errno might have in this situation. But that makes it impossible to recognize errors. One might argue that according to POSIX errno should be left unchanged if an entry is not found. Experiments on various Unix-like systems shows that lots of different values occur in this situation: 0, ENOENT, EBADF, ESRCH, EWOULDBLOCK, EPERM and probably others.

SOUVISEJÍCÍ

endgrent(3), fgetgrent(3), getgrent(3), getpwnam(3), setgrent(3), group(5)

2003-11-15