#include <sys/types.h> #include <grp.h> struct group *getgrent(void); void setgrent(void); void endgrent(void);
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
setgrent():
_XOPEN_SOURCE >= 500
|| /* Glibc since 2.19: */ _DEFAULT_SOURCE
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
getgrent(), endgrent():
Since glibc 2.22:
_XOPEN_SOURCE >= 500 || _DEFAULT_SOURCE
Glibc 2.21 and earlier
_XOPEN_SOURCE >= 500
|| /* Since glibc 2.12: */ _POSIX_C_SOURCE >= 200809L
|| /* Glibc <= 2.19: */ _BSD_SOURCE || _SVID_SOURCE
The setgrent() function rewinds to the beginning of the group database, to allow repeated scans.
The endgrent() function is used to close the group database after all processing has been performed.
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; /* NULL-terminated array of pointers
to names of group members */
};
For more information about the fields of this structure, see group(5).
Upon error, errno may be set. If one wants to check errno after the call, it should be set to zero before the call.
The return value may point to a static area, and may be overwritten by subsequent calls to getgrent(), getgrgid(3), or getgrnam(3). (Do not pass the returned pointer to free(3).)
| Interface | Attribute | Value |
| getgrent() | Thread safety |
MT-Unsafe race:grent
race:grentbuf locale
|
| setgrent(), endgrent() | Thread safety |
MT-Unsafe race:grent locale
|
In the above table, grent in race:grent signifies that if any of the functions setgrent(), getgrent(), or endgrent() are used in parallel in different threads of a program, then data races could occur.