sleep(1p)

1SLEEP(1P)                  POSIX Programmer's Manual                 SLEEP(1P)
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PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
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NAME

12       sleep - suspend execution for an interval
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SYNOPSIS

15       sleep time
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DESCRIPTION

18       The sleep utility shall suspend execution for  at  least  the  integral
19       number of seconds specified by the time operand.
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OPTIONS

22       None.
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OPERANDS

25       The following operand shall be supported:
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27       time   A  non-negative decimal integer specifying the number of seconds
28              for which to suspend execution.
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30

STDIN

32       Not used.
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INPUT FILES

35       None.
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ENVIRONMENT VARIABLES

38       The following environment  variables  shall  affect  the  execution  of
39       sleep:
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41       LANG   Provide  a  default value for the internationalization variables
42              that are unset or null. (See  the  Base  Definitions  volume  of
43              IEEE Std 1003.1-2001,  Section  8.2,  Internationalization Vari‐
44              ables for the precedence of internationalization variables  used
45              to determine the values of locale categories.)
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47       LC_ALL If  set  to a non-empty string value, override the values of all
48              the other internationalization variables.
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50       LC_CTYPE
51              Determine the locale for  the  interpretation  of  sequences  of
52              bytes  of  text  data as characters (for example, single-byte as
53              opposed to multi-byte characters in arguments).
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55       LC_MESSAGES
56              Determine the locale that should be used to  affect  the  format
57              and contents of diagnostic messages written to standard error.
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59       NLSPATH
60              Determine the location of message catalogs for the processing of
61              LC_MESSAGES .
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ASYNCHRONOUS EVENTS

65       If the sleep utility receives a SIGALRM signal, one  of  the  following
66       actions shall be taken:
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68        1. Terminate normally with a zero exit status.
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70        2. Effectively ignore the signal.
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72        3. Provide the default behavior for signals described in the ASYNCHRO‐
73           NOUS EVENTS section of Utility Description Defaults  .  This  could
74           include terminating with a non-zero exit status.
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76       The sleep utility shall take the standard action for all other signals.
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STDOUT

79       Not used.
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STDERR

82       The standard error shall be used only for diagnostic messages.
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OUTPUT FILES

85       None.
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EXTENDED DESCRIPTION

88       None.
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EXIT STATUS

91       The following exit values shall be returned:
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93        0     The  execution was successfully suspended for at least time sec‐
94              onds, or a SIGALRM signal was  received.  See  the  ASYNCHRONOUS
95              EVENTS section.
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97       >0     An error occurred.
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CONSEQUENCES OF ERRORS

101       Default.
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103       The following sections are informative.
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APPLICATION USAGE

106       None.
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EXAMPLES

109       The  sleep  utility  can  be  used to execute a command after a certain
110       amount of time, as in:
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113              (sleep 105; command) &
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115       or to execute a command every so often, as in:
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117
118              while true
119              do
120                  command    sleep 37
121              done
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RATIONALE

124       The exit status is allowed to be zero when sleep is interrupted by  the
125       SIGALRM signal because most implementations of this utility rely on the
126       arrival of that signal to notify them that the requested finishing time
127       has  been successfully attained.  Such implementations thus do not dis‐
128       tinguish this situation from  the  successful  completion  case.  Other
129       implementations  are  allowed  to catch the signal and go back to sleep
130       until the requested time expires or to provide the normal signal termi‐
131       nation procedures.
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133       As  with  all  other  utilities  that take integral operands and do not
134       specify subranges of allowed values, sleep is required by  this  volume
135       of  IEEE Std 1003.1-2001 to deal with time requests of up to 2147483647
136       seconds. This may mean that some implementations have to make  multiple
137       calls  to the delay mechanism of the underlying operating system if its
138       argument range is less than this.
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FUTURE DIRECTIONS

141       None.
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COPYRIGHT

148       Portions  of  this text are reprinted and reproduced in electronic form
149       from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
150       --  Portable  Operating  System  Interface (POSIX), The Open Group Base
151       Specifications Issue 6, Copyright (C) 2001-2003  by  the  Institute  of
152       Electrical  and  Electronics  Engineers, Inc and The Open Group. In the
153       event of any discrepancy between this version and the original IEEE and
154       The  Open Group Standard, the original IEEE and The Open Group Standard
155       is the referee document. The original Standard can be  obtained  online
156       at http://www.opengroup.org/unix/online.html .
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160IEEE/The Open Group                  2003                            SLEEP(1P)