sleep

- suspend execution for an interval

Synopsis

/usr/bin/sleep

/usr/bin/sleep seconds

ksh93

sleep seconds

Description

sleep suspends execution for at least the time in seconds specified by seconds or until a SIGALRM signal is received. The seconds operand can be specified as a floating point number but the actual granularity normally depends on the underlying system.

Operands

/usr/bin/sleep

The following operands are supported for /usr/bin/sleep and ksh93's sleep built-in command:

seconds

A non-negative floating-point number specifying the number of seconds for which to suspend execution. The floating-point number may be specified in all formats required by C99/XPG6, including constants such as "Inf" or "infinite".

ksh93

The following operands are supported:

time

Specify time in seconds as a floating point number. The actual granularity depends on the underlying system, normally around 1 millisecond.

Examples

Example 1 Suspending Command Execution

The following example executes a command after a certain amount of time:

example% (sleep 105; command)&

Example 2 Executing a Command Every So Often

The following example executes a command every so often:

example% while true do command sleep 37 done

Example 3 Suspend command execution forever (or until a SIGALRM signal is received)

example% sleep Inf

Example 4 Suspending command execution for 0.5 seconds

Suspending command execution for 0.5 seconds using an alternative floating-point representation for the value "0.5"

example% printf "%a\n" 0.5
0x1.0000000000000000000000000000p-01

example% sleep 0x1.0000000000000000000000000000p-01

Environment Variables

See environ(5) for descriptions of the following environment variables that affect the execution of sleep: LANG, LC_ALL, LC_CTYPE, LC_MESSAGES, and NLSPATH.

Exit Status

The following exit values are returned:

0

The execution was successfully suspended for at least time seconds, or a SIGALRM signal was received (see NOTES).

>0

An error has occurred.

Attributes

See attributes(5) for descriptions of the following attributes:

/usr/bin/sleep

ksh93

See Also

ksh93(1), wait(1), alarm(2), sleep(3C), attributes(5), environ(5), standards(5)

Notes

If the sleep utility receives a SIGALRM signal, one of the following actions is taken:

• Terminate normally with a zero exit status.

• Effectively ignore the signal.

The sleep utility takes the standard action for all other signals.

The behavior for input values such as "NaN" (not-a-number) or negative values is undefined.