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Manual Pages  — GETPWENT


getpwent, getpwent_r, getpwnam, getpwnam_r, getpwuid, getpwuid_r, setpassent, setpwent, endpwent – password database operations



Standard C Library (libc, -lc)


#include <sys/types.h>
#include <pwd.h>

struct passwd *

getpwent_r(struct passwd *pwd, char *buffer, size_t bufsize, struct passwd **result);

struct passwd *
getpwnam(const char *login);

getpwnam_r(const char *name, struct passwd *pwd, char *buffer, size_t bufsize, struct passwd **result);

struct passwd *
getpwuid(uid_t uid);

getpwuid_r(uid_t uid, struct passwd *pwd, char *buffer, size_t bufsize, struct passwd **result);

setpassent(int stayopen);




These functions operate on the password database file which is described in passwd(5). Each entry in the database is defined by the structure passwd found in the include file <pwd.h>:
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 */
        int     pw_fields;      /* internal: fields filled in */

The functions getpwnam() and getpwuid() search the password database for the given login name or user uid, respectively, always returning the first one encountered.

The getpwent() function sequentially reads the password database and is intended for programs that wish to process the complete list of users.

The functions getpwent_r(), getpwnam_r(), and getpwuid_r() are thread-safe versions of getpwent(), getpwnam(), and getpwuid(), respectively. The caller must provide storage for the results of the search in the pwd, buffer, bufsize, and result arguments. When these functions are successful, the pwd argument will be filled-in, and a pointer to that argument will be stored in result. If an entry is not found or an error occurs, result will be set to NULL.

The setpassent() function accomplishes two purposes. First, it causes getpwent() to ``rewind'' to the beginning of the database. Additionally, if stayopen is non-zero, file descriptors are left open, significantly speeding up subsequent accesses for all of the routines. (This latter functionality is unnecessary for getpwent() as it does not close its file descriptors by default.)

It is dangerous for long-running programs to keep the file descriptors open as the database will become out of date if it is updated while the program is running.

The setpwent() function is identical to setpassent() with an argument of zero.

The endpwent() function closes any open files.

These routines have been written to ``shadow'' the password file, e.g.amp; allow only certain programs to have access to the encrypted password. If the process which calls them has an effective uid of 0, the encrypted password will be returned, otherwise, the password field of the returned structure will point to the string ‘*’.


The functions getpwent(), getpwnam(), and getpwuid() return a valid pointer to a passwd structure on success or NULL if the entry is not found or if an error occurs. If an error does occur, errno will be set. Note that programs must explicitly set errno to zero before calling any of these functions if they need to distinguish between a non-existent entry and an error. The functions getpwent_r(), getpwnam_r(), and getpwuid_r() return 0 if no error occurred, or an error number to indicate failure. It is not an error if a matching entry is not found. (Thus, if result is NULL and the return value is 0, no matching entry exists.)

The setpassent() function returns 0 on failure and 1 on success. The endpwent() and setpwent() functions have no return value.


/etc/pwd.db The insecure password database file
/etc/spwd.db The secure password database file
  The current password file
/etc/passwd A Version 7 format password file


The historic function setpwfile(3), which allowed the specification of alternate password databases, has been deprecated and is no longer available.


These routines may fail for any of the errors specified in open(2), dbopen(3), socket(2), and connect(2), in addition to the following:
  The buffer specified by the buffer and bufsize arguments was insufficiently sized to store the result. The caller should retry with a larger buffer.


getlogin(2), getgrent(3), nsswitch.conf(5), passwd(5), pwd_mkdb(8), vipw(8), yp(8)


The getpwent(), getpwnam(), getpwnam_r(), getpwuid(), getpwuid_r(), setpwent(), and endpwent() functions conform to IEEE Std 1003.1-96 ("POSIX.1").


The getpwent(), getpwnam(), getpwuid(), setpwent(), and endpwent() functions appeared in AT&T v7 . The setpassent() function appeared in BSD 4.3 Reno . The getpwent_r(), getpwnam_r(), and getpwuid_r() functions appeared in FreeBSD 5.1 .


The functions getpwent(), getpwnam(), and getpwuid(), leave their results in an internal static object and return a pointer to that object. Subsequent calls to the same function will modify the same object.

The functions getpwent(), getpwent_r(), endpwent(), setpassent(), and setpwent() are fairly useless in a networked environment and should be avoided, if possible. The getpwent() and getpwent_r() functions make no attempt to suppress duplicate information if multiple sources are specified in nsswitch.conf(5).

GETPWENT (3) April 16, 2003

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