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Top Forums Shell Programming and Scripting Difference between using "echo" builtin and /bin/echo Post 302334365 by ulidtko on Wednesday 15th of July 2009 10:38:09 AM
Old 07-15-2009
Difference between using "echo" builtin and /bin/echo

So in my shell i execute:
Code:
 { while true; do echo string; sleep 1; done } | read line

This waits one second and returns.
But
Code:
 { while true; do /bin/echo string; sleep 1; done } | read line

continues to run, and doesn't stop until i kill it explicitly.

I have tried this in bash as well as zsh, but the behaviour is the same. I wonder, why do these statements execute in such different manner? I understand, that in the first case right part of the pipe finishes after reading single line from its stdin, and terminates. Consequently, the interpretor terminates the whole pipe. But why does this scenario not apply to the second case?..
 

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SLEEP(3)								 1								  SLEEP(3)

sleep - Delay execution

SYNOPSIS
int sleep (int $seconds) DESCRIPTION
Delays the program execution for the given number of $seconds. PARAMETERS
o $seconds - Halt time in seconds. RETURN VALUES
Returns zero on success, or FALSE on error. If the call was interrupted by a signal, sleep(3) returns a non-zero value. On Windows, this value will always be 192 (the value of the WAIT_IO_COMPLETION constant within the Windows API). On other platforms, the return value will be the number of seconds left to sleep. ERRORS
/EXCEPTIONS If the specified number of $seconds is negative, this function will generate a E_WARNING. CHANGELOG
+--------+---------------------------------------------------+ |Version | | | | | | | Description | | | | +--------+---------------------------------------------------+ | 5.3.4 | | | | | | | Before PHP 5.3.4, on Windows, sleep(3) always | | | returns NULL when sleep has occurred, regardless | | | of whether the sleep was interrupted or not. | | | | +--------+---------------------------------------------------+ EXAMPLES
Example #1 sleep(3) example <?php // current time echo date('h:i:s') . " "; // sleep for 10 seconds sleep(10); // wake up ! echo date('h:i:s') . " "; ?> This example will output (after 10 seconds) 05:31:23 05:31:33 SEE ALSO
usleep(3), time_nanosleep(3), time_sleep_until(3), set_time_limit(3). PHP Documentation Group SLEEP(3)
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