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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 *stream, struct passwd *pwbuf, char *buf,
                       size_t buflen, struct passwd **pwbufp);

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

       getpwent_r(),
           Since glibc 2.19:
               _DEFAULT_SOURCE
           Glibc 2.19 and earlier:
               _BSD_SOURCE || _SVID_SOURCE
       fgetpwent_r():
           Since glibc 2.19:
               _DEFAULT_SOURCE
           Glibc 2.19 and earlier:
               _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
       setpwent(3).  The latter reads the next passwd entry from stream.

       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.

ATTRIBUTES

       For an explanation of the terms used in this section, see attributes(7).

       ┌──────────────┬───────────────┬─────────────────────────────┐
       │InterfaceAttributeValue                       │
       ├──────────────┼───────────────┼─────────────────────────────┤
       │getpwent_r()  │ Thread safety │ MT-Unsafe race:pwent locale │
       ├──────────────┼───────────────┼─────────────────────────────┤
       │fgetpwent_r() │ Thread safety │ MT-Safe                     │
       └──────────────┴───────────────┴─────────────────────────────┘
       In the above table, pwent in race:pwent signifies that if any of the functions setpwent(),
       getpwent(),  endpwent(),  or  getpwent_r()  are used in parallel in different threads of a
       program, then data races could occur.

CONFORMING TO

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

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       found at https://www.kernel.org/doc/man-pages/.