PHP exec 不返回 awk 輸出

Question

我正在嘗試通過 PHP 獲取以下 awk 命令的輸出，但沒有輸出

$time_ref = date("Y-m-d\TH:i:s",strtotime(date('c', (time() - 80)))); //2020-03-29T21:00:30

$s_string = 'awk \'$0 > "'.$time_ref.'" && $0 ~ "AAA4311A01A404C4E21ABE55"\' /var/log/syslog | tail -1';  

echo shell_exec($s_string);

直接從控制台運行 awk 它可以工作：

pi@raspberrypi:/var/log $ awk '$0 > "2020-03-30T10:06:28" && $0 ~ "AAA4311A01A404C4E21ABE55"' syslog

2020-03-30T10:07:40.300908+02:00 RadioBridge ESP-RSL: RESULT = {"RfRaw":{"Data":"AAA4311A01A404C4E21ABE55"}}

關於為什么它不能從 PHP 工作的任何建議？

Answer 1

There are many solution. 
1) if  you run the PHP file in web, you should set the permission to the awk file. 
2) we should set the path of the "awk"
$PATH = "real path";
putenv("PATH=$PATH");
$_string = "./awk ...."

Thanks.