sleep.1p (5202B)
- '\" et
- .TH SLEEP "1P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
- .\"
- .SH PROLOG
- This manual page is part of the POSIX Programmer's Manual.
- The Linux implementation of this interface may differ (consult
- the corresponding Linux manual page for details of Linux behavior),
- or the interface may not be implemented on Linux.
- .\"
- .SH NAME
- sleep
- \(em suspend execution for an interval
- .SH SYNOPSIS
- .LP
- .nf
- sleep \fItime\fR
- .fi
- .SH DESCRIPTION
- The
- .IR sleep
- utility shall suspend execution for at least the integral number of
- seconds specified by the
- .IR time
- operand.
- .SH OPTIONS
- None.
- .SH OPERANDS
- The following operand shall be supported:
- .IP "\fItime\fR" 10
- A non-negative decimal integer specifying the number of seconds for
- which to suspend execution.
- .SH STDIN
- Not used.
- .SH "INPUT FILES"
- None.
- .SH "ENVIRONMENT VARIABLES"
- The following environment variables shall affect the execution of
- .IR sleep :
- .IP "\fILANG\fP" 10
- Provide a default value for the internationalization variables that are
- unset or null. (See the Base Definitions volume of POSIX.1\(hy2017,
- .IR "Section 8.2" ", " "Internationalization Variables"
- for the precedence of internationalization variables used to determine
- the values of locale categories.)
- .IP "\fILC_ALL\fP" 10
- If set to a non-empty string value, override the values of all the
- other internationalization variables.
- .IP "\fILC_CTYPE\fP" 10
- 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).
- .IP "\fILC_MESSAGES\fP" 10
- .br
- Determine the locale that should be used to affect the format and
- contents of diagnostic messages written to standard error.
- .IP "\fINLSPATH\fP" 10
- Determine the location of message catalogs for the processing of
- .IR LC_MESSAGES .
- .SH "ASYNCHRONOUS EVENTS"
- If the
- .IR sleep
- utility receives a SIGALRM signal, one of the following actions shall
- be taken:
- .IP " 1." 4
- Terminate normally with a zero exit status.
- .IP " 2." 4
- Effectively ignore the signal.
- .IP " 3." 4
- Provide the default behavior for signals described in the ASYNCHRONOUS
- EVENTS section of
- .IR "Section 1.4" ", " "Utility Description Defaults".
- This could include terminating with a non-zero exit status.
- .P
- The
- .IR sleep
- utility shall take the standard action for all other signals.
- .SH STDOUT
- Not used.
- .SH STDERR
- The standard error shall be used only for diagnostic messages.
- .SH "OUTPUT FILES"
- None.
- .SH "EXTENDED DESCRIPTION"
- None.
- .SH "EXIT STATUS"
- The following exit values shall be returned:
- .IP "\00" 6
- The execution was successfully suspended for at least
- .IR time
- seconds, or a SIGALRM signal was received. See the ASYNCHRONOUS EVENTS
- section.
- .IP >0 6
- An error occurred.
- .SH "CONSEQUENCES OF ERRORS"
- Default.
- .LP
- .IR "The following sections are informative."
- .SH "APPLICATION USAGE"
- None.
- .SH EXAMPLES
- The
- .IR sleep
- utility can be used to execute a command after a certain amount of
- time, as in:
- .sp
- .RS 4
- .nf
- (sleep 105; \fIcommand\fP) &
- .fi
- .P
- .RE
- .P
- or to execute a command every so often, as in:
- .sp
- .RS 4
- .nf
- while true
- do
- \fIcommand\fP
- sleep 37
- done
- .fi
- .P
- .RE
- .SH RATIONALE
- The exit status is allowed to be zero when
- .IR 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.
- .P
- As with all other utilities that take integral operands and do not
- specify subranges of allowed values,
- .IR sleep
- is required by this volume of POSIX.1\(hy2017 to deal with
- .IR time
- requests of up to 2\|147\|483\|647 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.
- .SH "FUTURE DIRECTIONS"
- None.
- .SH "SEE ALSO"
- .IR "\fIwait\fR\^"
- .P
- The Base Definitions volume of POSIX.1\(hy2017,
- .IR "Chapter 8" ", " "Environment Variables"
- .P
- The System Interfaces volume of POSIX.1\(hy2017,
- .IR "\fIalarm\fR\^(\|)",
- .IR "\fIsleep\fR\^(\|)"
- .\"
- .SH COPYRIGHT
- Portions of this text are reprinted and reproduced in electronic form
- from IEEE Std 1003.1-2017, Standard for Information Technology
- -- Portable Operating System Interface (POSIX), The Open Group Base
- Specifications Issue 7, 2018 Edition,
- Copyright (C) 2018 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 .
- .PP
- Any typographical or formatting errors that appear
- in this page are most likely
- to have been introduced during the conversion of the source files to
- man page format. To report such errors, see
- https://www.kernel.org/doc/man-pages/reporting_bugs.html .