These functions shall retrieve information about users.
The getpwent() function shall return a pointer to a structure containing
the broken-out fields of an entry in the user database. Each entry in the user
database contains a passwd structure. When first called,
getpwent() shall return a pointer to a passwd structure
containing the first entry in the user database. Thereafter, it shall return a
pointer to a passwd structure containing the next entry in the user
database. Successive calls can be used to search the entire user database.
If an end-of-file or an error is encountered on reading, getpwent() shall
return a null pointer.
An implementation that provides extended security controls may impose further
implementation-defined restrictions on accessing the user database. In
particular, the system may deny the existence of some or all of the user
database entries associated with users other than the caller.
The setpwent() function effectively rewinds the user database to allow
The endpwent() function may be called to close the user database when
processing is complete.
These functions need not be reentrant. A function that is not required to be
reentrant is not required to be thread-safe.
The following example uses the getpwent() function to get successive
entries in the user database, returning a pointer to a passwd structure
that contains information about each user. The call to endpwent()
closes the user database and cleans up.
These functions are provided due to their historical usage. Applications should
avoid dependencies on fields in the password database, whether the database is
a single file, or where in the file system name space the database resides.
Applications should use getpwuid() whenever possible because it avoids
Portions of this text are reprinted and reproduced in electronic form from IEEE
Std 1003.1, 2003 Edition, Standard for Information Technology -- Portable
Operating System Interface (POSIX), The Open Group Base Specifications Issue
6, Copyright (C) 2001-2003 by the Institute of Electrical and Electronics
Engineers, Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard, the original
IEEE and The Open Group Standard is the referee document. The original
Standard can be obtained online at http://www.opengroup.org/unix/online.html