shell 管道两端的程序，并不是左边的程序先启动 - yanbin's Blog
shell 管道两端的程序，并不是左边的程序先启动
yanbin
posted @ 2015年3月15日 23:05
in Linux-使用
, 1572 阅读
$ ps aux | grep "demo"
这条命令中的 ps 先启动，会导致程序异常退出。
因为写一个没有读端的管道，引发 SIGPIPE 信号，SIGPIPE 信号默认行为是终止程序的执行。
管道的创建者(shell) 先创建管道，启动 read 管道的程序 (grep), 再启动 write 管道的程序(ps aux).
读一个没有写端的管道会阻塞，grep 可以接受阻塞。
$ ps aux | grep "demo" | grep -v "grep"
这样的命令相当于: (ps aux | grep "demo") | grep -v "grep".
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