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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 *restrict pwbuf,
                      char *restrict buf, size_t buflen,
                      struct passwd **restrict pwbufp);
       int fgetpwent_r(FILE *restrict stream, struct passwd *restrict pwbuf,
                      char *restrict buf, size_t buflen,
                      struct passwd **restrict 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  di‐
       rectory 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).

       ┌──────────────┬───────────────┬─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┐
       │Interface     │ Attribute     │ Value                                                                                                                           │
       ├──────────────┼───────────────┼─────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────┤
       │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 dif‐
       ferent 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.

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

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

           setpwent();
           while (1) {
               i = getpwent_r(&pw, buf, sizeof(buf), &pwp);
               if (i)
                   break;
               printf("%s (%jd)\tHOME %s\tSHELL %s\n", pwp->pw_name,
                      (intmax_t) 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)

GNU                                                                            2021-03-22                                                                  GETPWENT_R(3)