| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON | The Linux Programming Interface |
GETPWENT_R(3) Linux Programmer's Manual GETPWENT_R(3)
getpwent_r, fgetpwent_r - get passwd file entry reentrantly
#include <pwd.h>
int getpwent_r(struct passwd *pwbuf, char *buf,
size_t buflen, struct passwd **pwbufp);
int fgetpwent_r(FILE *fp, 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
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 the stream fp.
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.
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.
ENOENT No more entries.
ERANGE Insufficient buffer space supplied. Try again with larger buffer.
These functions are GNU extensions, done in a style resembling the POSIX
version of functions like getpwnam_r(3). Other systems use 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);
The function getpwent_r() is not really reentrant since it shares the reading
position in the stream with all other threads.
#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);
}
fgetpwent(3), getpw(3), getpwent(3), getpwnam(3), getpwuid(3), putpwent(3),
passwd(5)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
GNU 2010-10-21 GETPWENT_R(3)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface