The Institute of Electrical and Electronics Engineers (IEEE) and The Open Group, have given us permission to reprint portions of their documentation. In the following statement, the phrase ``this text'' refers to portions of the system documentation. Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1, 2013 Edition, Standard for Information Technology -- Portable Operating System Interface (POSIX), The Open Group Base Specifications Issue 7, Copyright (C) 2013 by the Institute of Electri- cal and Electronics Engineers, Inc and The Open Group. (This is POSIX.1-2008 with the 2013 Technical Corrigendum 1 applied.) 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.unix.org/online.html . This notice shall appear on any product containing this material. Redistribution of this material is permitted so long as this notice and the corresponding notices within each POSIX manual page are retained on any distribution, and the nroff source is included. Modifications to the text are permitted so long as any conflicts with the standard are clearly marked as such in the text.