bash 是否 $! 在 shell 脚本中意味着什么
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Does $! mean something in shell scripting
提问by pRAShANT
Does $!exists in bash/shell script, if yes, please inform for what it is used for. And why it gives blank when echo $!is run on the command line?
是否$! 存在于 bash/shell 脚本中，如果是，请告知它的用途。为什么它echo $!在命令行上运行时给出空白？
回答by anubhava
In addition to other answer, this echo
除了其他答案，这个回声
echo $!
Will print blank if you haven't yet run any process in backgroundin current shell. If you now run:
如果您尚未在当前 shell 的后台运行任何进程，则将打印为空白。如果你现在运行：
date &
echo $!
Then it will print something like (i.e. process id of last executed background process):
然后它将打印类似的内容（即上次执行的后台进程的进程 ID）：
47833
回答by user000001
$!is the PID of the last program your shell ran in the background
$!是您的 shell 在后台运行的最后一个程序的 PID
回答by Ranjithkumar T
$! - shows last process ID which has started in background.
$! - 显示在后台启动的最后一个进程 ID。
