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GETGRENT_R(3)              Linux Programmer's Manual             GETGRENT_R(3)

       getgrent_r, fgetgrent_r - get group file entry reentrantly

       #include <grp.h>

       int getgrent_r(struct group *gbuf, char *buf,
                      size_t buflen, struct group **gbufp);

       int fgetgrent_r(FILE *fp, struct group *gbuf, char *buf,
                       size_t buflen, struct group **gbufp);

   Feature Test Macro Requirements for glibc (see feature_test_macros(7)):

       getgrent_r(): _GNU_SOURCE
       fgetgrent_r(): _SVID_SOURCE

       The functions getgrent_r() and fgetgrent_r() are the reentrant versions
       of getgrent(3) and fgetgrent(3).  The former reads the next group entry
       from  the stream initialized by setgrent(3).  The latter reads the next
       group entry from the stream fp.

       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).

       The nonreentrant functions return a pointer to  static  storage,  where
       this  static  storage contains further pointers to group name, password
       and members.  The reentrant functions described here return all of that
       in caller-provided buffers.  First of all there is the buffer gbuf that
       can hold a struct group.  And next the buffer buf of size  buflen  that
       can hold additional strings.  The result of these functions, the struct
       group read from the stream, is stored in the provided buffer *gbuf, and
       a pointer to this struct group is returned in *gbufp.

       On  success,  these  functions  return 0 and *gbufp is a pointer to the
       struct group.  On error, these functions  return  an  error  value  and
       *gbufp is NULL.

       ENOENT No more entries.

       ERANGE Insufficient  buffer space supplied.  Try again with larger buf-

       These functions are GNU extensions, done  in  a  style  resembling  the
       POSIX  version of functions like getpwnam_r(3).  Other systems use pro-

           struct group *getgrent_r(struct group *grp, char *buf,
                                    int buflen);

       or, better,

           int getgrent_r(struct group *grp, char *buf, int buflen,
                          FILE **gr_fp);

       The function getgrent_r() is not really reentrant since it  shares  the
       reading position in the stream with all other threads.

       #define _GNU_SOURCE
       #include <grp.h>
       #include <stdio.h>
       #include <stdlib.h>
       #define BUFLEN 4096

           struct group grp, *grpp;
           char buf[BUFLEN];
           int i;

           while (1) {
               i = getgrent_r(&grp, buf, BUFLEN, &grpp);
               if (i)
               printf("%s (%d):", grpp->gr_name, grpp->gr_gid);
               for (i = 0; ; i++) {
                   if (grpp->gr_mem[i] == NULL)
                   printf(" %s", grpp->gr_mem[i]);

       fgetgrent(3),   getgrent(3),   getgrgid(3),  getgrnam(3),  putgrent(3),

       This page is part of release 3.74 of the Linux  man-pages  project.   A
       description  of  the project, information about reporting bugs, and the
       latest    version    of    this    page,    can     be     found     at

GNU                               2014-08-19                     GETGRENT_R(3)

Czas wygenerowania: 0.00053 sek.

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