getpwent_r (3)
Leading comments
Copyright (c) 2003 Andries Brouwer (aeb@cwi.nl) %%%LICENSE_START(GPLv2+_DOC_FULL) This is free documentation; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU General Public License's references to "object code" and "executables" are to be interpreted as the output of any document formatting or typesetting system, including i...
NAME
getpwent_r, fgetpwent_r - get passwd file entry reentrantlySYNOPSIS
#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(),
_BSD_SOURCE || _SVID_SOURCE
fgetpwent_r():
_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).| 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.
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); }