getpwent_r

Section: C Library Functions (3)
Updated: 202-0-08
Index Return to Main Contents

---

 

NAME

getpwent_r, fgetpwent_r - get passwd file entry reentrantly  

LIBRARY

Standard C library (libc,~-lc)  

SYNOPSIS

#include <pwd.h>
int getpwent_r(size_t size;
               struct passwd *restrict pwbuf,
               char buf[restrict size], size_t size,
               struct passwd **restrict pwbufp);
int fgetpwent_r(size_t size;
               FILE *restrict stream, struct passwd *restrict pwbuf,
               char buf[restrict size], size_t size,
               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 directory and shell. The reentrant functions described here return all of that in calle-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

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	M-Unsafe race:pwent locale
fgetpwent_r()	Thread safety	M-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.  

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);  

STANDARDS

None.  

HISTORY

These functions are done in a style resembling the POSIX version of functions like getpwnam_r(3).  

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();
    while (1) {
        i = getpwent_r(&pw, buf, sizeof(buf), &pwp);
        if (i)
            break;
        printf("%s (%jd)[rs]tHOME %s[rs]tSHELL %s[rs]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)

---

 

Index

NAME

LIBRARY

SYNOPSIS

DESCRIPTION

RETURN VALUE

ERRORS

ATTRIBUTES

VERSIONS

STANDARDS

HISTORY

NOTES

EXAMPLES

SEE ALSO