bash - 这行 "BUILD_TARGET=${1:-none}"在 shell 脚本中意味着什么？

Question

我刚开始学习 shell 脚本，所以如果这太基础而不能在这里问，请原谅我。我想运行这个 sh 脚本 (https://github.com/daid/Cura/blob/SteamEngine/package.sh)。 但我无法理解这一行 (BUILD_TARGET=${1:-none}) 的作用？

摘录如下:

#!/usr/bin/env bash

set -e
set -u

# This script is to package the Cura package for Windows/Linux and Mac OS X
# This script should run under Linux and Mac OS X, as well as Windows with Cygwin.

#############################
# CONFIGURATION
#############################

##Select the build target
BUILD_TARGET=${1:-none}
#BUILD_TARGET=win32
#BUILD_TARGET=darwin
#BUILD_TARGET=debian_i386
#BUILD_TARGET=debian_amd64
#BUILD_TARGET=debian_armhf
#BUILD_TARGET=freebsd

##Do we need to create the final archive
ARCHIVE_FOR_DISTRIBUTION=1
##Which version name are we appending to the final archive
export BUILD_NAME=15.04.6
TARGET_DIR=Cura-${BUILD_NAME}-${BUILD_TARGET}

##Which versions of external programs to use
WIN_PORTABLE_PY_VERSION=2.7.2.1

当我试图通过在 Cygwin 中运行来查看它是如何工作时，它抛出以下错误，

$ bash package.sh
package.sh: line 2: $'\r': command not found
: invalid option 3: set: -
set: usage: set [-abefhkmnptuvxBCHP] [-o option-name] [--] [arg ...]
: invalid option 4: set: -
set: usage: set [-abefhkmnptuvxBCHP] [-o option-name] [--] [arg ...]
package.sh: line 5: $'\r': command not found
package.sh: line 8: $'\r': command not found
package.sh: line 12: $'\r': command not found
package.sh: line 21: $'\r': command not found
package.sh: line 27: $'\r': command not found
package.sh: line 30: $'\r': command not found
package.sh: line 48: syntax error near unexpected token `$'{\r''
'ackage.sh: line 48: `{

我在 Cygwin 中缺少什么？

更新 1:我通过将行结尾转换为与 unix 兼容的结尾来解决“找不到命令”的问题。更多信息可以在这里找到，'\r': command not found - .bashrc / .bash_profile

Answer 1

$1 是第一个命令行参数

${1:-none} 表示如果第一个命令行参数未设置或为空，则替换为“none”。
否则，值为第一个命令行参数被替换。

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更多信息，查看[ shell parameter expansion ] .