DESCRIPTION
These functions operate on the password database file which is described in passwd(5). Each entry in the database is defined by the structure
.Vt passwd found in the include file
.In 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 */
intpw_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It is dangerous for long-running programs to keep the file descriptors open as the database will become out of date if it is updated while the program is running.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. 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 ‘*’.
RETURN VALUES
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.
FILES
