PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT

GETGRNAM(3P)              POSIX Programmer's Manual             GETGRNAM(3P)

PROLOG         top

       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.

NAME         top

       getgrnam, getgrnam_r — search group database for a name

SYNOPSIS         top

       #include <grp.h>

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

DESCRIPTION         top

       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
       database 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 location pointed to by result on
       error or if the requested entry is not found.

RETURN VALUE         top

       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
       getgrnam().

       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.

ERRORS         top

       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
              open.

       ENFILE The maximum allowable number of files is currently open in the
              system.

       The getgrnam_r() function may fail if:

       ERANGE Insufficient storage was supplied via buffer and bufsize to
              contain the data to be referenced by the resulting group
              structure.

       The following sections are informative.

EXAMPLES         top

       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);
           size_t len;
           if (initlen == −1)
               /* Default initial length. */
               len = 1024;
           else
               len = (size_t) initlen;
           struct group result;
           struct group *resultp;
           char *buffer = malloc(len);
           if (buffer == NULL)
               ...handle error...
           int e;
           while ((e = getgrnam_r("somegroup", &result, buffer, len, &resultp))
                   == ERANGE)
               {
               size_t newlen = 2 * len;
               if (newlen < len)
                   ...handle error...
               len = newlen;
               char *newbuffer = realloc(buffer, len);
               if (newbuffer == NULL)
                   ...handle error...
               buffer = newbuffer;
               }
           if (e != 0)
               ...handle error...
           free (buffer);

APPLICATION USAGE         top

       Applications wishing to check for error situations should set errno
       to 0 before calling getgrnam().  If errno is set on return, an error
       occurred.

       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.

RATIONALE         top

       None.

FUTURE DIRECTIONS         top

       None.

SEE ALSO         top

       endgrent(3p), getgrgid(3p), sysconf(3p)

       The Base Definitions volume of POSIX.1‐2008, grp.h(0p),
       sys_types.h(0p)

COPYRIGHT         top

       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 Electrical 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.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                 2013                        GETGRNAM(3P)

Pages that refer to this page: grp.h(0p)newgrp(1p)endgrent(3p)getgrgid(3p)