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

NAME
       getgrentr, fgetgrentr - get group file entry reentrantly

SYNOPSIS
       #include 

       int getgrentr(struct group *gbuf, char *buf,
                      sizet buflen, struct group **gbufp);

       int fgetgrentr(FILE *fp, struct group *gbuf, char *buf,
                       sizet buflen, struct group **gbufp);

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

       getgrentr(): GNUSOURCE
       fgetgrentr(): SVIDSOURCE

DESCRIPTION
       The functions getgrentr() and fgetgrentr() 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  as follows:

           struct group {
               char    *grname;     /* group name */
               char    *grpasswd;   /* group password */
               gidt    grgid;      /* group ID */
               char   **grmem;      /* 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.

RETURN VALUE
       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.

ERRORS
       ENOENT No more entries.

       ERANGE Insufficient  buffer space supplied.  Try again with larger buf‐
              fer.

CONFORMING TO
       These functions are GNU extensions, done  in  a  style  resembling  the
       POSIX  version of functions like getpwnamr(3).  Other systems use pro‐
       totype

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

       or, better,

           int getgrentr(struct group *grp, char *buf, int buflen,
                          FILE **grfp);

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

EXAMPLE
       #define GNUSOURCE
       #include 
       #include 
       #include 
       #define BUFLEN 4096

       int
       main(void)
       {
           struct group grp, *grpp;
           char buf[BUFLEN];
           int i;

           setgrent();
           while (1) {
               i = getgrentr(&grp, buf, BUFLEN, &grpp);
               if (i)
                   break;
               printf("%s (%d):", grpp->grname, grpp->grgid);
               for (i = 0; ; i++) {
                   if (grpp->grmem[i] == NULL)
                       break;
                   printf(" %s", grpp->grmem[i]);
               }
               printf("\n");
           }
           endgrent();
           exit(EXITSUCCESS);
       }

SEE ALSO
       fgetgrent(3),   getgrent(3),   getgrgid(3),  getgrnam(3),  putgrent(3),
       group(5)

COLOPHON
       This page is part of release 3.53 of the Linux  man-pages  project.   A
       description  of  the project, and information about reporting bugs, can
       be found at http://www.kernel.org/doc/man-pages/.



GNU                               2010-10-21                     GETGRENTR(3)