10-15-2003
Maybe a couple more examples will make it clear.
echo hello
echo hello > garbage.txt
echo hello > /dev/tty
echo hello > /dev/null
The first one will display hello for you to see, and the second one will send the word hello into a file. I think that you got that much.
The third one is explicitly doing for the shell did automatically. /dev/tty is not your ordinary file, it is a "special file". Instead of being stored in a file on disk, a special little program called a driver is going to get that "hello" string. The tty driver will figure out how to make the characters appear on your screen. And then it will tell the OS, ok...that "hello" string went to the device.
The fourth one is also going to a special file and again a driver will get the string "hello". But this driver is just going to tell the OS, ok...that "hello" string went to the device. But there is no device and the null driver did not try to do anything. It just tosses the characters away.
You can read from /dev/tty. And the driver will wait for you to type something and read those characters and send them on.
You can read from /dev/null too, but the driver will always claim that there is no data.
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TOUCH(3) 1 TOUCH(3)
touch - Sets access and modification time of file
SYNOPSIS
bool touch (string $filename, [int $time = time()], [int $atime])
DESCRIPTION
Attempts to set the access and modification times of the file named in the $filename parameter to the value given in $time. Note that the
access time is always modified, regardless of the number of parameters.
If the file does not exist, it will be created.
PARAMETERS
o $filename
- The name of the file being touched.
o $time
- The touch time. If $time is not supplied, the current system time is used.
o $atime
- If present, the access time of the given filename is set to the value of $atime. Otherwise, it is set to the value passed to the
$time parameter. If neither are present, the current system time is used.
RETURN VALUES
Returns TRUE on success or FALSE on failure.
CHANGELOG
+--------+---------------------------------------------------+
|Version | |
| | |
| | Description |
| | |
+--------+---------------------------------------------------+
| 5.3.0 | |
| | |
| | It became possible to change the modification |
| | time of a directory under Windows. |
| | |
+--------+---------------------------------------------------+
EXAMPLES
Example #1
touch(3) example
<?php
if (touch($filename)) {
echo $filename . ' modification time has been changed to present time';
} else {
echo 'Sorry, could not change modification time of ' . $filename;
}
?>
Example #2
touch(3) using the $time parameter
<?php
// This is the touch time, we'll set it to one hour in the past.
$time = time() - 3600;
// Touch the file
if (!touch('some_file.txt', $time)) {
echo 'Whoops, something went wrong...';
} else {
echo 'Touched file with success';
}
?>
NOTES
Note
Note that time resolution may differ from one file system to another.
Warning
Prior to PHP 5.3.0 it was not possible to change the modification time of a directory with this function under Windows.
PHP Documentation Group TOUCH(3)