如何在Bash中用引号引起来的字符串中使用环境变量 [英] How to use an environment variable inside a quoted string in Bash

问题描述

我在bash脚本中尝试了以下各种形式:

I've tried various forms of the following in a bash script:

#!/bin/bash
svn diff $@ --diff-cmd /usr/bin/diff -x "-y -w -p -W $COLUMNS"

但是我无法正确地扩展COLUMNS环境变量的语法.

But I can't get the syntax to correctly expand the COLUMNS environment variable.

我尝试了以下各种形式:

I've tried various forms of the following:

svn diff $@ --diff-cmd /usr/bin/diff -x '-y -w -p -W $COLUMNS'

和

svn diff $@ --diff-cmd /usr/bin/diff -x '-y -w -p -W ${COLUMNS}'

和

eval svn diff $@ --diff-cmd /usr/bin/diff -x "-y -w -p -W $COLUMNS"

建议?

推荐答案

如果不确定，您可能会在终端上使用"cols"请求，而忘记了"COLUMNS":

If unsure, you might use the 'cols' request on the terminal, and forget COLUMNS:

COLS=$(tput cols)

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