重定向/管道到读取命令 [英] Redirect / pipe into read command

问题描述

这是我上一个关于 SO .我仍在尝试从另一个脚本shallowScript中命令一个脚本deepScript并处理其输出，然后再显示在终端上.这是一个代码示例:

This is a follow-up to my previous question on SO. I am still trying to command a script deepScript from within another script shallowScript and process its output before display on terminal. Here is a code sample:

deepScript.sh

#!/bin/zsh
print "Hello - this is deepScript"
read "ans?Reading : "
print $ans

shallowScript.sh

#!/bin/zsh

function __process {
    while read input; do
        echo $input | sed "s/e/E/g"
    done }

print "Hello - this is shallowScript"
. ./deepScript.sh |& __process

(此语法的结果以及下面粘贴的2个替代方法的结果)

[UPDATE]

我为上次重定向. ./deepScript.sh |& __process尝试了其他语法，每种语法都有不同的结果，但是当然，它们都不是我想要的.我将粘贴每种语法以及./shallowScript.sh的结果输出(在read等待输入时我在其中键入"input")，以及到目前为止的发现.

I have tried alternative syntaxes for last redirection . ./deepScript.sh |& __process and each syntax has a different outcome, but of course none of them is the one I want. I'll just paste each syntax and the resulting output of ./shallowScript.sh (where I typed "input" when read was waiting for an input), together with my findings so far.

选项1: . ./deepScript.sh |& __process

通过此链接，似乎正在运行. ./deepScript.sh从子shell，但不是__process.输出:

From this link, it seems that . ./deepScript.sh is run from a subshell, but not __process. Output:

zsh : ./shallowScript.sh
Hello - this is shallowScript
HEllo - this is dEEpScript
input
REading : input

基本上，前两行按预期方式打印，然后脚本不等待提示REading :的打印，而是直接等待stdin输入，然后然后打印提示并执行print $ans

Basically, the first two lines are printed as expected, then instead of printing the prompt REading :, the script directly waits for the stdin input, and then prints the prompt and executes print $ans.

选项2: __process < <(. ./deepScript.sh)

Zsh的联机帮助页表示(. ./deepScript.sh)将运行作为子过程.在我看来，这类似于选项1 .输出:

Zsh's manpage indicates that (. ./deepScript.sh) will run as a subprocess. To me, that looks similar to Option 1. Output:

Hello - this is shallowScript
Reading : HEllo - this is dEEpScript
input
input

因此，内 . ./deepScript.sh，它将在打印(脚本第2行)之前打印read的提示(脚本第3行).奇怪.

So, within . ./deepScript.sh, it prints read's prompt (script line 3) before the print (script line 2). Strange.

选项3: __process < =(. ./deepScript.sh)

根据相同的联机帮助页，(. ./deepScript.sh)这里将其输出发送到一个临时文件，然后将其注入__process(我不知道是否有子进程).输出:

According to the same manpage, (. ./deepScript.sh) here sends its output to a temp file, which is then injected in __process (I don't know if there is a subprocess or not). Output:

Hello - this is shallowScript
Reading : input
HEllo - this is dEEpScript
input

同样，deepScript的第3行在第2行之前打印到终端，但是现在它等待读取完成.

Again, deepScript's line 3 prints to the terminal before line 2, but now it waits for the read to be complete.

两个问题:

• 这应该在意料之中吗?
• 是否有修复程序或解决方法?

推荐答案

观察到的延迟源于两个因素:

The observed delay stems from two factors:

1. deepScript.sh和process异步运行
2. read在返回之前先读完整行

1. deepScript.sh and process run asynchronously
2. read reads a complete line before returning

deepScript.sh将提示写入标准错误，但没有换行符.然后，它会等待您的输入，而process继续等待写整行，以便对read的调用可以完成.

deepScript.sh writes the prompt to standard error, but without a newline. It then waits for your input while process continues to wait for a full line to be written so that its call to read can finish.

这篇关于重定向/管道到读取命令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！