NAME
getpwent_r, fgetpwent_r - get passwd file entry reentrantly
SYNOPSIS
#define _GNU_SOURCE
#include <pwd.h>
I int getpwent_r(struct passwd * pwbuf , char * buf ,
I size_t buflen , struct passwd ** pwbufp );
I int fgetpwent_r(FILE * fp , struct passwd * pwbuf , char * buf ,
I size_t buflen , struct passwd ** pwbufp );
DESCRIPTION
The functions
R getpwent_r ()
and
R 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
given as parameter.
The
passwd structure is defined in
<pwd.h>
as follows:
struct passwd {
char *pw_name; /* user name */
char *pw_passwd; /* user password */
uid_t pw_uid; /* user ID */
gid_t pw_gid; /* group ID */
char *pw_gecos; /* real name */
char *pw_dir; /* home directory */
char *pw_shell; /* shell program */
};
The non-reentrant 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
ERANGE
Insufficient buffer space supplied.
Try again with larger buffer.
CONFORMING TO
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);
NOTES
The function
R 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);
}
SEE ALSO