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Linux 2.6 - man page for fgetpwent_r (linux section 3)

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

NAME
       getpwent_r, fgetpwent_r - get passwd file entry reentrantly

SYNOPSIS
       #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

DESCRIPTION
       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 setp-
       went(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.

RETURN VALUE
       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.

ERRORS
       ENOENT No more entries.

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

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

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

       or, better,

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

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

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

       int
       main(void)
       {
	   struct passwd pw, *pwp;
	   char buf[BUFLEN];
	   int i;

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

SEE ALSO
       fgetpwent(3), getpw(3), getpwent(3), getpwnam(3), getpwuid(3), putpwent(3), passwd(5)

COLOPHON
       This page is part of release 3.55 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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