GETPWENT(3) Library Functions Manual GETPWENT(3)NAME
getpwent, getpwnam, getpwuid, setpwent, endpwent, setpwfile - password file routines
SYNOPSIS
#include <pwd.h>
struct passwd *getpwent(void)
struct passwd *getpwnam(const char *name)
struct passwd *getpwuid(uid_t uid)
int setpwent(void)
void endpwent(void)
void setpwfile(const char *file)
DESCRIPTION
These functions are used to obtain information from the password file. They return this information in a struct passwd as defined by
<pwd.h>:
struct passwd {
char *pw_name; /* login name */
char *pw_passwd; /* encrypted password */
uid_t pw_uid; /* numeric user id */
gid_t pw_gid; /* numeric group id */
char *pw_gecos; /* user full name and other info */
char *pw_dir; /* user's home directory */
char *pw_shell; /* name of the user's shell */
};
Getpwent() reads the password file entry by entry. Getpwnam() scans the entire password file for the user with the given name. Getpwuid()
looks for the first user with the given uid. The setpwent() and endpwent() functions are used to open and later close the password file.
With setpwfile() one can specify the file to read other than the normal password file. This only sets the name, the next setpwent() call
will open the file. Do not touch the file name while it is active. Use setpwfile(NULL) to revert back to the normal password file.
The usual way to scan the password file is (error checking omitted):
setpwent();
while ((pw = getpwent()) != NULL)
if (appropriate_test(pw)) break;
endpwent();
The pw variable contains the entry that is wanted if non-NULL. The getpwnam() and getpwuid() functions are implemented as in this example,
with error checking of course.
Getpwent() calls setpwent() if this has not yet been done. Setpwent() first calls endpwent() if the password file is still open. (Other
implementations may simply rewind the file.)
FILES
/etc/passwd The password file database.
SEE ALSO cuserid(3), getlogin(3), getgrent(3), passwd(5).
DIAGNOSTICS
Setpwent() has the same return value and error codes as the open(2) call it uses to open the password file. The getxxx() functions return
NULL on end of file, entry not found, or error. You can set errno to zero before the call and check it after.
NOTES
All getxxx() routines return a pointer to static storage that is overwritten in each call.
Only getpwnam() and getpwuid() are defined by POSIX. The _MINIX_SOURCE macro must be defined before including <pwd.h> to make the other
functions visible. The pw_passwd and pw_gecos fields are also not defined by POSIX, but are always visible. Portable code cannot reliably
detect errors by setting errno to zero. Under Minix it is better to make a getpwent() scan if you need to look up several user-id's or
names, but portable code had better use several getpwuid() or getpwnam() calls. The getpwent() is usually available on other systems, but
may be very expensive.
AUTHOR
Kees J. Bot (kjb@cs.vu.nl)
GETPWENT(3)
Check Out this Related Man Page
GETPWENT(3) Library Functions Manual GETPWENT(3)NAME
getpwent, getpwnam, getpwuid, setpassent, setpwfile, setpwent, endpwent - get password file entries
SYNOPSIS
#include <sys/types.h>
#include <pwd.h>
struct passwd *getpwent()
struct passwd *getpwnam(login)
char *login;
struct passwd *getpwuid(uid)
uid_t uid;
int setpassent(stayopen)
int stayopen;
void setpwfile(file)
char *file;
int setpwent()
void endpwent()
DESCRIPTION
Getpwent, getpwuid, and getpwnam each return a pointer to a structure containing the broken-out fields of a line in the password file.
This structure is defined by the include file <pwd.h>, and contains the following fields:
struct passwd {
char *pw_name; /* user name */
char *pw_passwd; /* encrypted password */
uid_t pw_uid; /* user uid */
gid_t pw_gid; /* user gid */
time_t pw_change; /* password change time */
char *pw_class; /* user access class */
char *pw_gecos; /* Honeywell login info */
char *pw_dir; /* home directory */
char *pw_shell; /* default shell */
time_t pw_expire; /* account expiration */
};
These fields are more completely described in passwd(5).
Getpwnam and getpwuid search the password database for a matching user name or user uid, respectively, returning the first one encountered.
Identical user names or user uids may result in undefined behavior.
Getpwent sequentially reads the password database and is intended for programs that wish to step through the complete list of users.
All three routines will open the password file for reading, if necessary.
Setpwfile changes the default password file to file, thus allowing the use of alternate password files.
Setpassent opens the file or rewinds it if it is already open. If stayopen is non-zero, file descriptors are left open, significantly
speeding up subsequent calls. This functionality is unnecessary for getpwent as it doesn't close its file descriptors by default. It
should also be noted that it is dangerous for long-running programs to use this functionality as the password file may be updated by
chpass(1), passwd(1), or vipw(8).
Setpwent is identical to setpassent with an argument of zero.
Endpwent closes any open files.
These routines have been written to ``shadow'' the password file, e.g. allow only certain programs to have access to the encrypted pass-
word. This is done by using the mkpasswd(8) program, which creates ndbm(3) databases that correspond to the password file, with the single
exception that, rather than storing the encrypted password in the database, it stores the offset in the password file where the encrypted
password may be found. Getpwent, getpwnam, and getpwuid will use the ndbm files in preference to the ``real'' password files, only reading
the password file itself, to obtain the encrypted password, if the process is running with an effective user id equivalent to super-user.
If the password file itself is protected, and the ndbm files are not, this makes the password available only to programs running with
super-user privileges.
FILES
/etc/passwd
SEE ALSO getlogin(3), getgrent(3), ndbm(3), passwd(5)DIAGNOSTICS
The routines getpwent, getpwnam, and getpwuid, return a null pointer on EOF or error. Setpassent and setpwent return 0 on failure and 1 on
success. Endpwent and setpwfile have no return value.
BUGS
All information is contained in a static buffer which is overwritten by each new call. It must be copied elsewhere to be retained.
Intermixing calls to getpwent with calls to getpwnam or getpwuid, or intermixing calls to getpwnam and getpwuid, after using setpassent to
require that file descriptors be left open, may result in undefined behavior.
The routines getpwent, endpwent, setpassent, and setpwent are fairly useless in a networked environment and should be avoided, if possible.
7th Edition February 23, 1989 GETPWENT(3)