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   getpwent_r    ( 3 )

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Имя (Name)

getpwent_r, fgetpwent_r - get passwd file entry reentrantly

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Синопсис (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

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Описание (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.

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Возвращаемое значение (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.

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Ошибки (Error)

ENOENT No more entries.

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

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Атрибуты (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 different threads of a program, then data races could occur.

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Стандарты (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);

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Примечание (Note)

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

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Примеры (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);
       }

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Смотри также (See also)

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

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