"shopt -s lastpipe"如何影响bash脚本行为? [英] how does `shopt -s lastpipe` affect bash script behavior?

问题描述

我正在尝试使 ffcast 屏幕投射工具bash 4.1向后兼容.

I am trying to make ffcast screen casting tool bash 4.1 backwards compatible.

，并在此 ffcast.bash 脚本中，有一条线

and in this ffcast.bash script, there is oneline

shopt -s extglob lastpipe

lastpipe选项仅在bash 4.3之后可用，我该如何模拟它的效果?

lastpipe option is only available after bash 4.3, what can I do to emulate its effect?

推荐答案

lastpipe (顺便说一下，在bash 4.2中引入)只能通过不使用管道来模拟.您需要在当前Shell中显式运行管道的最后一条命令，然后从任一过程替换中重定向其输入

lastpipe (introduced in bash 4.2, by the way) can only be simulated by not using a pipe. You need to explicitly run the last command of the pipe line in the current shell, and redirect its input from either a process substitution

# foo | bar | baz becomes ...
baz < <(foo | bar)

或命名管道(也符合POSIX)

or a named pipe (which is POSIX-compliant as well)

# foo | bar | baz becomes ...
mkfifo baz_input
foo | bar > baz_input &
baz < baz_input

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