zsh和bash之间的I/O重定向差异 [英] I/O redirection differences between zsh and bash

问题描述

我在命令行上使用zsh，但是我编写的shell脚本运行bash，以便它们可移植.

I use zsh at the command-line but the shell scripts I write run bash so that they are portable.

当我意识到这种差异时，我正在此处了解有关IO重定向的信息:

I was learning about IO redirection from here when I realized this difference:

请注意，该命令只是任意命令，其第一行输出在stderr之上，第二行输出在stdout之上.

Note that the command is just an arbitrary one whose first line of output is over stderr and the second line comes over stdout.

zsh:

% ls -ld /tmp /tnt 1>&2 2>&1  | sed -e 's/^/++/'
ls: /tnt: No such file or directory
++ls: /tnt: No such file or directory
lrwxr-xr-x@ 1 root  wheel  11 Oct 19  2012 /tmp -> private/tmp
++lrwxr-xr-x@ 1 root  wheel  11 Oct 19  2012 /tmp -> private/tmp

bash:

bash-3.2$ ls -ld /tmp /tnt 1>&2 2>&1  | sed -e 's/^/++/'
ls: /tnt: No such file or directory
lrwxr-xr-x@ 1 root  wheel  11 Oct 19  2012 /tmp -> private/tmp

我很难弄清zsh的输出.

此外，在Linux上，zsh的输出顺序略有不同:

Also, on a Linux the output order's slightly different for zsh:

% ls -ld /tmp /tnt 1>&2 2>&1  | sed -e 's/^/++/'
ls: cannot access /tnt: No such file or directory
drwxrwxrwt. 13 root root 4096 Dec 19 23:11 /tmp
++ls: cannot access /tnt: No such file or directory
++drwxrwxrwt. 13 root root 4096 Dec 19 23:11 /tmp

但是

bash的输出是相同的.

bash output is identical though.

zsh中的更多实验:

% ls -ld /tmp /tnt 1>&2 | sed -e 's/^/++/'
ls: /tnt: No such file or directory
lrwxr-xr-x@ 1 root  wheel  11 Oct 19  2012 /tmp -> private/tmp
++lrwxr-xr-x@ 1 root  wheel  11 Oct 19  2012 /tmp -> private/tmp

% ls -ld /tmp /tnt 2>&1 | sed -e 's/^/++/'
++ls: /tnt: No such file or directory
++lrwxr-xr-x@ 1 root  wheel  11 Oct 19  2012 /tmp -> private/tmp

那里的最后一个产生与bash相同的结果.

That last one there produces identical results to bash.

我认为我更喜欢在研究zsh滴答声之前从内而外地学习bash的行为，但这并不是很理想，因为机会至少是我期望做的IO重定向的一半我肯定会想从zsh提示符尝试尝试一下.而且我实际上在zsh上投入了很多钱，因为我有大量的自定义插件，这时要大力改回bash将是一项巨大的努力.

I figure I should prefer learning bash's behavior inside-out before delving into how zsh ticks, but this isn't really ideal because chances are at least half of the IO redirection I expect to be doing will be spur-of-the-moment hacks that I surely will want to try from the zsh prompt. And I'm actually pretty invested in zsh because I have a ton of custom plugins and it would be a major effort at this point to do a big switch back to bash.

推荐答案

这是由于zsh的 mult_ios功能.

在zsh中，当fd重定向两次时，zsh实现内部的tee:

In zsh, when a fd is redirected twice, zsh implements an internal tee:

ls > foo > bar

将ls的输出发送到管道，并且zsh将其输入到foo和bar.

Sends the output of ls to a pipe and zsh feeds it to both foo and bar.

它可能会与管道混淆.

ls > foo | cmd

将输出发送到foo和cmd.

您可以通过以下方式禁用它:

You can disable it with:

setopt no_mult_ios

这篇关于zsh和bash之间的I/O重定向差异的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！