GETGRENT(3)

GETGRENT(3) | Library Functions Manual | GETGRENT(3)

# NAME

`getgrent`, `getgrent_r`, `getgrgid`, `getgrgid_r`, `getgrnam`, `getgrnam_r`, `setgroupent`, `setgrent`, `endgrent` —
group database operations

# LIBRARY

Standard C Library (libc, -lc)

# SYNOPSIS

`#include <grp.h>`

struct group *
`getgrent`(void);

int
`getgrent_r`(struct group *grp, char *buffer, size_t buflen, struct group **result);

struct group *
`getgrgid`(gid_t gid);

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

struct group *
`getgrnam`(const char *name);

int
`getgrnam_r`(const char *name, struct group *grp, char *buffer, size_t buflen, struct group **result);

int
`setgroupent`(int stayopen);

void
`setgrent`(void);

void
`endgrent`(void);

# DESCRIPTION

These functions operate on the group database which is described in group(5). Each line of the database is defined by the structure group found in the include file `<grp.h>`:

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

The functions `getgrnam`() and `getgrgid`() search the group database for the given group name pointed to by name or the group id pointed to by gid, respectively, returning the first one encountered. Identical group names or group ids may result in undefined behavior.

The `getgrent`() function sequentially reads the group database and is intended for programs that wish to step through the complete list of groups.

All three functions will open the group file for reading, if necessary.

The functions `getgrnam_r`(), `getgrgid_r`(), and `getgrent_r`() act like their non re-entrant counterparts respectively, updating the contents of grp and storing a pointer to that in result, and returning `0`. Storage used by grp is allocated from buffer, which is buflen bytes in size. If the requested entry cannot be found, result will point to `NULL` and `0` will be returned. If an error occurs, a non-zero error number will be returned and result will point to `NULL`. Calling `getgrent_r`() from multiple threads will result in each thread reading a disjoint portion of the group database.

The `setgroupent`() function opens the file, or rewinds it if it is already open. If stayopen is non-zero, file descriptors are left open, significantly speeding functions subsequent calls. This functionality is unnecessary for `getgrent`() as it doesn't close its file descriptors by default. It should also be noted that it is dangerous for long-running programs to use this functionality as the group file may be updated.

The `setgrent`() function is equivalent to `setgroupent`() with an argument of zero.

The `endgrent`() function closes any open files.

# RETURN VALUES

The functions `getgrgid`(), `getgrnam`(), and `getgrent`() return a valid pointer to a group structure on success and a `NULL` pointer if the entry was not found or an error occurred. If an error occurred, the global variable `errno` is set to indicate the nature of the failure.

The functions `getgrgid_r`(), `getgrnam_r`(), and `getgrent_r`() return `0` on success or entry not found, and non-zero on failure, setting the global variable `errno` to indicate the nature of the failure.

The `setgroupent`() function returns the value 1 if successful, otherwise the value 0 is returned, setting the global variable `errno` to indicate the nature of the failure.

The `endgrent`() and `setgrent`() functions have no return value.

# FILES

/etc/group
  group database file

# COMPATIBILITY

The historic function `setgrfile`(), which allowed the specification of alternative group databases, has been deprecated and is no longer available.

# ERRORS

The following error codes may be set in errno for `getgrent`, `getgrent_r`, `getgrnam`, `getgrnam_r`, `getgrgid`, `getgrgid_r`, and `setgroupent`:

[`EINTR`]
  A signal was caught during the database search.
[`EIO`]
  An I/O error has occurred.
[`EMFILE`]
  The limit on open files for this process has been reached.
[`ENFILE`]
  The system limit on open files has been reached.

The following error code may be set in errno for `getgrent_r`, `getgrnam_r`, and `getgrgid_r`:

[`ERANGE`]
  The resulting struct group does not fit in the space defined by `buffer` and `buflen`

Other `errno` values may be set depending on the specific database backends.

# SEE ALSO

getpwent(3), group(5), nsswitch.conf(5)

# STANDARDS

The `getgrgid`() and `getgrnam`() functions conform to IEEE Std 1003.1-1990 (“POSIX.1”). The `getgrgid_r`() and `getgrnam_r`() functions conform to IEEE Std 1003.1c-1995 (“POSIX.1c”). The `endgrent`(), `getgrent`(), and `setgrent`() functions conform to X/Open Portability Guide Issue 4, Version 2 (“XPG4.2”) and IEEE Std 1003.1-2004 (“POSIX.1”) (XSI extension).

# HISTORY

The functions `endgrent`(), `getgrent`(), `getgrgid`(), `getgrnam`(), and `setgrent`() appeared in Version 7 AT&T UNIX. The functions `setgrfile`() and `setgroupent`() appeared in 4.3BSD-Reno. The functions `getgrgid_r`() and `getgrnam_r`() appeared in NetBSD 3.0.

# BUGS

The functions `getgrent`(), `getgrgid`(), `getgrnam`(), `setgroupent`() and `setgrent`() leave their results in an internal static object and return a pointer to that object. Subsequent calls to the same function will modify the same object.

The functions `getgrent`(), `endgrent`(), `setgroupent`(), and `setgrent`() are fairly useless in a networked environment and should be avoided, if possible. `getgrent`() makes no attempt to suppress duplicate information if multiple sources are specified in nsswitch.conf(5)

February 7, 2018 | NetBSD 9.0