SLEEP(P) POSIX Programmer's Manual SLEEP(P)
sleep - suspend execution for an interval
The sleep utility shall suspend execution for at least the integral number of seconds
specified by the time operand.
The following operand shall be supported:
time A non-negative decimal integer specifying the number of seconds for which to sus-
The following environment variables shall affect the execution of sleep:
LANG 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, Inter-
nationalization Variables for the precedence of internationalization variables used
to determine the values of locale categories.)
LC_ALL If set to a non-empty string value, override the values of all the other interna-
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 argu-
Determine the locale that should be used to affect the format and contents of diag-
nostic messages written to standard error.
Determine the location of message catalogs for the processing of LC_MESSAGES .
If the sleep utility receives a SIGALRM signal, one of the following actions shall be
1. Terminate normally with a zero exit status.
2. Effectively ignore the signal.
3. Provide the default behavior for signals described in the ASYNCHRONOUS EVENTS section
of Utility Description Defaults . This could include terminating with a non-zero exit
The sleep utility shall take the standard action for all other signals.
The standard error shall be used only for diagnostic messages.
The following exit values shall be returned:
0 The execution was successfully suspended for at least time seconds, or a SIGALRM
signal was received. See the ASYNCHRONOUS EVENTS section.
>0 An error occurred.
CONSEQUENCES OF ERRORS
The following sections are informative.
The sleep utility can be used to execute a command after a certain amount of time, as in:
(sleep 105; command) &
or to execute a command every so often, as in:
command sleep 37
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 implementa-
tions 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.
wait , the System Interfaces volume of IEEE Std 1003.1-2001, alarm(), sleep()
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 orig-
inal Standard can be obtained online at http://www.opengroup.org/unix/online.html .
IEEE/The Open Group 2003 SLEEP(P)