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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 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.

       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 buffer.

       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,

           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), putpwent(3), passwd(5)

       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 http://www.kernel.org/doc/man-pages/.

GNU                                         2010-10-21                              GETPWENT_R(3)

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