GETGRNAM(3P) POSIX Programmer's Manual GETGRNAM(3P)PROLOG
This manual page is part of the POSIX Programmer's Manual. The Linux
implementation of this interface may differ (consult the corresponding
Linux manual page for details of Linux behavior), or the interface may
not be implemented on Linux.
getgrnam, getgrnam_r — search group database for a name
struct group *getgrnam(const char *name);
int getgrnam_r(const char *name, struct group *grp, char *buffer,
size_t bufsize, struct group **result);
The getgrnam() function shall search the group database for an entry
with a matching name.
The getgrnam() function need not be thread-safe.
The getgrnam_r() function shall update the group structure pointed to
by grp and store a pointer to that structure at the location pointed to
by result. The structure shall contain an entry from the group data‐
base with a matching name. Storage referenced by the group structure
is allocated from the memory provided with the buffer parameter, which
is bufsize bytes in size. A call to sysconf(_SC_GETGR_R_SIZE_MAX)
returns either −1 without changing errno or an initial value suggested
for the size of this buffer. A null pointer is returned at the loca‐
tion pointed to by result on error or if the requested entry is not
The getgrnam() function shall return a pointer to a struct group with
the structure defined in <grp.h> with a matching entry if one is found.
The getgrnam() function shall return a null pointer if either the
requested entry was not found, or an error occurred. On error, errno
shall be set to indicate the error.
The application shall not modify the structure to which the return
value points, nor any storage areas pointed to by pointers within the
structure. The returned pointer, and pointers within the structure,
might be invalidated or the structure or the storage areas might be
overwritten by a subsequent call to getgrent(), getgrgid(), or getgr‐
The getgrnam_r() function shall return zero on success or if the
requested entry was not found and no error has occurred. If any error
has occurred, an error number shall be returned to indicate the error.
The getgrnam() and getgrnam_r() functions may fail if:
EIO An I/O error has occurred.
EINTR A signal was caught during getgrnam().
EMFILE All file descriptors available to the process are currently
ENFILE The maximum allowable number of files is currently open in the
The getgrnam_r() function may fail if:
ERANGE Insufficient storage was supplied via buffer and bufsize to con‐
tain the data to be referenced by the resulting group structure.
The following sections are informative.
Note that sysconf(_SC_GETGR_R_SIZE_MAX) may return −1 if there is no
hard limit on the size of the buffer needed to store all the groups
returned. This example shows how an application can allocate a buffer
of sufficient size to work with getgrnam_r().
long int initlen = sysconf(_SC_GETGR_R_SIZE_MAX);
if (initlen == −1)
/* Default initial length. */
len = 1024;
len = (size_t) initlen;
struct group result;
struct group *resultp;
char *buffer = malloc(len);
if (buffer == NULL)
while ((e = getgrnam_r("somegroup", &result, buffer, len, &resultp))
size_t newlen = 2 * len;
if (newlen < len)
len = newlen;
char *newbuffer = realloc(buffer, len);
if (newbuffer == NULL)
buffer = newbuffer;
if (e != 0)
Applications wishing to check for error situations should set errno to
0 before calling getgrnam(). If errno is set on return, an error
The getgrnam_r() function is thread-safe and shall return values in a
user-supplied buffer instead of possibly using a static data area that
may be overwritten by each call.
Portable applications should take into account that it is usual for an
implementation to return −1 from sysconf() indicating that there is no
maximum for _SC_GETGR_R_SIZE_MAX.
SEE ALSOendgrent(), getgrgid(), sysconf()
The Base Definitions volume of POSIX.1‐2008, <grp.h>, <sys_types.h>
Portions of this text are reprinted and reproduced in electronic form
from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology
-- Portable Operating System Interface (POSIX), The Open Group Base
Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri‐
cal and Electronics Engineers, Inc and The Open Group. (This is
POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) In the
event of any discrepancy between this version and the original IEEE and
The Open Group Standard, the original IEEE and The Open Group Standard
is the referee document. The original Standard can be obtained online
at http://www.unix.org/online.html .
Any typographical or formatting errors that appear in this page are
most likely to have been introduced during the conversion of the source
files to man page format. To report such errors, see https://www.ker‐
IEEE/The Open Group 2013 GETGRNAM(3P)