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Which is more efficient - sleep or infinite while?
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sleep(1) General Commands Manual sleep(1) NAME
sleep - Suspends execution for at least the specified time SYNOPSIS
sleep seconds STANDARDS
Interfaces documented on this reference page conform to industry standards as follows: sleep: XCU5.0 Refer to the standards(5) reference page for more information about industry standards and associated tags. OPTIONS
None OPERANDS
Non-negative integer specifying the number of seconds for which execution is to be suspended. DESCRIPTION
The sleep command suspends execution of a process for at least the interval specified by seconds, which can range from 0 to 2,147,483,647 seconds. Depending on system activity, the actual time of suspension may be longer. See the sleep(3) reference page. [Tru64 UNIX] seconds can be entered as a non-negative decimal, octal, or hexadecimal value. NOTES
If sleep receives a SIGALARM signal before process execution has resumed, sleep takes one of the following actions: Terminates normally with a 0 (zero) exit status. (See the sleep(3) reference page for more information.) Ignores the signal Performs default processing EXIT STATUS
The following exit values are returned: Execution was successfully suspended for at least the requested time, or a SIGALARM signal was received. An error occurred. EXAMPLES
To display a message at 4-minute intervals for 20 minutes, create a shell script called remind containing the following: for i do sleep 240; echo $i sleep 240; echo $i sleep 240; echo $i sleep 240; echo $i sleep 240; echo $i done To display the message Try calling NHK at 4-minute intervals, enter: remind 'Try calling NHK' To run a command at regular intervals, create a shell script containing the following: while true do date sleep 60 done This displays the date and time once a minute. To execute a command after a specified interval, enter the following; (sleep 3600; echo Time's up) & This displays the message "Time's up" after one hour. ENVIRONMENT VARIABLES
The following environment variables affect the execution of sleep: Provides a default value for the internationalization variables that are unset or null. If LANG is unset or null, the corresponding value from the default locale is used. If any of the internationalization vari- ables contain an invalid setting, the utility behaves as if none of the variables had been defined. If set to a non-empty string value, overrides the values of all the other internationalization variables. Determines the locale for the interpretation of sequences of bytes of text data as characters (for example, single-byte as opposed to multibyte characters in arguments). Determines the locale for the for- mat and contents of diagnostic messages written to standard error. Determines the location of message catalogues for the processing of LC_MESSAGES. SEE ALSO
Commands: wait(1) Functions: alarm(3), pause(3), sigaction(2), sleep(3) Standards: standards(5) sleep(1)
