The following environment variables shall affect the execution of sleep:
Provide a default value for the internationalization
variables that are unset or null. (See the Base Definitions volume of
IEEE Std 1003.1-2001, Section 8.2, Internationalization
Variables for the precedence of internationalization variables used to
determine the values of locale categories.)
If set to a non-empty string value, override the values of
all the other internationalization variables.
Determine the locale for the interpretation of sequences of
bytes of text data as characters (for example, single-byte as opposed to
multi-byte characters in arguments).
Determine the locale that should be used to affect the
format and contents of diagnostic messages written to standard error.
Determine the location of message catalogs for the
processing of LC_MESSAGES.
The exit status is allowed to be zero when sleep is interrupted by the
SIGALRM signal because most implementations of this utility rely on the
arrival of that signal to notify them that the requested finishing time has
been successfully attained. Such implementations thus do not distinguish this
situation from the successful completion case. Other implementations are
allowed to catch the signal and go back to sleep until the requested time
expires or to provide the normal signal termination procedures.
As with all other utilities that take integral operands and do not specify
subranges of allowed values, sleep is required by this volume of
IEEE Std 1003.1-2001 to deal with time requests of up to
2147483647 seconds. This may mean that some implementations have to make
multiple calls to the delay mechanism of the underlying operating system if
its argument range is less than this.
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