getpwent_r3

Usage

#include <pwd.h>

    Since glibc 2.19:
        _DEFAULT_SOURCE
    glibc 2.19 and earlier:
        _BSD_SOURCE || _SVID_SOURCE

    Since glibc 2.19:
        _DEFAULT_SOURCE
    glibc 2.19 and earlier:
        _SVID_SOURCE

Library

Standard C library (libc, -lc)

Overview

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 size 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

Attributes

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

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.

Versions

Other systems use the prototype

struct passwd *
getpwent_r(struct passwd *pwd, char buf[.size], int size);

or, better,

int
getpwent_r(struct passwd *pwd, char buf[.size], int size,
           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 <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#define BUFLEN 4096
int
main(void)
{
    struct passwd pw;
    struct passwd *pwp;
    char buf[BUFLEN];
    int i;
    setpwent();
    for (;;) {
        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);
}