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

       getpwent_r, fgetpwent_r - get passwd file entry reentrantly

       #include <pwd.h>

       int getpwent_r(struct passwd *pwbuf, char *buf,
		      size_t buflen, struct passwd **pwbufp);

       int fgetpwent_r(FILE *fp, struct passwd *pwbuf, char *buf,
		       size_t buflen, struct passwd **pwbufp);

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

       getpwent_r(), _BSD_SOURCE || _SVID_SOURCE
       fgetpwent_r(): _SVID_SOURCE

       The functions getpwent_r() and fgetpwent_r() are the reentrant versions
       of getpwent(3) and fgetpwent(3).	 The  former  reads  the  next	passwd
       entry from the stream initialized by setpwent(3).  The latter reads the
       next passwd entry from the stream fp.

       The passwd structure is defined in <pwd.h> as follows:

	   struct passwd {
	       char    *pw_name;      /* username */
	       char    *pw_passwd;    /* user password */
	       uid_t	pw_uid;	      /* user ID */
	       gid_t	pw_gid;	      /* group ID */
	       char    *pw_gecos;     /* user information */
	       char    *pw_dir;	      /* home directory */
	       char    *pw_shell;     /* shell program */

       For more information about the fields of this structure, see passwd(5).

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

       On success, these functions return 0 and *pwbufp is a  pointer  to  the
       struct  passwd.	 On  error,  these functions return an error value and
       *pwbufp 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 passwd *
	   getpwent_r(struct passwd *pwd, char *buf, int buflen);

       or, better,

	   getpwent_r(struct passwd *pwd, char *buf, int buflen,
		      FILE **pw_fp);

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

       #define _GNU_SOURCE
       #include <pwd.h>
       #include <stdio.h>
       #define BUFLEN 4096

	   struct passwd pw, *pwp;
	   char buf[BUFLEN];
	   int i;

	   while (1) {
	       i = getpwent_r(&pw, buf, BUFLEN, &pwp);
	       if (i)
	       printf("%s (%d)\tHOME %s\tSHELL %s\n", pwp->pw_name,
		      pwp->pw_uid, pwp->pw_dir, pwp->pw_shell);

       fgetpwent(3), getpw(3), getpwent(3),  getpwnam(3),  getpwuid(3),	 putp‐
       went(3), passwd(5)

       This  page  is  part of release 3.54 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			 GETPWENT_R(3)

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