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.
10

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 sec‐
28                 onds for which to suspend execution.
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STDIN

31       Not used.
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INPUT FILES

34       None.
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ENVIRONMENT VARIABLES

37       The following environment  variables  shall  affect  the  execution  of
38       sleep:
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40       LANG      Provide  a  default  value for the internationalization vari‐
41                 ables that are unset or null. (See the Base Definitions  vol‐
42                 ume  of POSIX.1‐2017, Section 8.2, Internationalization Vari‐
43                 ables for the precedence  of  internationalization  variables
44                 used to determine the values of locale categories.)
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46       LC_ALL    If  set  to  a non-empty string value, override the values of
47                 all the other internationalization variables.
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49       LC_CTYPE  Determine the locale for the interpretation of  sequences  of
50                 bytes of text data as characters (for example, single-byte as
51                 opposed to multi-byte characters in arguments).
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53       LC_MESSAGES
54                 Determine the locale that should be used to affect the format
55                 and  contents  of  diagnostic  messages  written  to standard
56                 error.
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58       NLSPATH   Determine the location of message catalogs for the processing
59                 of LC_MESSAGES.
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ASYNCHRONOUS EVENTS

62       If  the  sleep  utility receives a SIGALRM signal, one of the following
63       actions shall be taken:
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65        1. Terminate normally with a zero exit status.
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67        2. Effectively ignore the signal.
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69        3. Provide the default behavior for signals described in the ASYNCHRO‐
70           NOUS  EVENTS  section of Section 1.4, Utility Description Defaults.
71           This could include terminating with a non-zero exit status.
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73       The sleep utility shall take the standard action for all other signals.
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STDOUT

76       Not used.
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STDERR

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

82       None.
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EXTENDED DESCRIPTION

85       None.
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EXIT STATUS

88       The following exit values shall be returned:
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90        0    The execution was successfully suspended for at least  time  sec‐
91             onds,  or  a  SIGALRM  signal  was received. See the ASYNCHRONOUS
92             EVENTS section.
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94       >0    An error occurred.
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CONSEQUENCES OF ERRORS

97       Default.
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99       The following sections are informative.
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APPLICATION USAGE

102       None.
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EXAMPLES

105       The sleep utility can be used to execute  a  command  after  a  certain
106       amount of time, as in:
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108
109           (sleep 105; command) &
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111       or to execute a command every so often, as in:
112
113
114           while true
115           do
116               command
117               sleep 37
118           done
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RATIONALE

121       The  exit status is allowed to be zero when sleep is interrupted by the
122       SIGALRM signal because most implementations of this utility rely on the
123       arrival of that signal to notify them that the requested finishing time
124       has been successfully attained. Such implementations thus do  not  dis‐
125       tinguish  this  situation  from  the  successful completion case. Other
126       implementations are allowed to catch the signal and go  back  to  sleep
127       until the requested time expires or to provide the normal signal termi‐
128       nation procedures.
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130       As with all other utilities that take  integral  operands  and  do  not
131       specify  subranges  of allowed values, sleep is required by this volume
132       of POSIX.1‐2017 to deal with time requests of up to 2147483647 seconds.
133       This  may mean that some implementations have to make multiple calls to
134       the delay mechanism of the underlying operating system if its  argument
135       range is less than this.
136

FUTURE DIRECTIONS

138       None.
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COPYRIGHT

149       Portions of this text are reprinted and reproduced in  electronic  form
150       from  IEEE Std 1003.1-2017, Standard for Information Technology -- Por‐
151       table Operating System Interface (POSIX), The Open Group Base  Specifi‐
152       cations  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of
153       Electrical and Electronics Engineers, Inc and The Open Group.   In  the
154       event of any discrepancy between this version and the original IEEE and
155       The Open Group Standard, the original IEEE and The Open Group  Standard
156       is  the  referee document. The original Standard can be obtained online
157       at http://www.opengroup.org/unix/online.html .
158
159       Any typographical or formatting errors that appear  in  this  page  are
160       most likely to have been introduced during the conversion of the source
161       files to man page format. To report such errors,  see  https://www.ker‐
162       nel.org/doc/man-pages/reporting_bugs.html .
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166IEEE/The Open Group                  2017                            SLEEP(1P)