Question

我尝试使用ENV中的替换字符串创建脚本文件，但也想阻止某些字符串转义

export PLACEHOLDER1="myPlaceholder1Value"
export PLACEHOLDER2="myPlaceholder2Value"
sudo /bin/su -c "cat << EOF > /etc/init.d/my-script
#!/bin/bash
#
### BEGIN INIT INFO
# Provides:          my-script
# Required-Start:    \$remote_fs \$syslog
# Required-Stop:     \$remote_fs \$syslog
# Should-Start:      \$network \$time
# Should-Stop:       \$network \$time
# Default-Start:     2 3 4 5 
# Default-Stop:      0 1 6
# Short-Description: blabla
# Description:       bla bla desc
#
### END INIT INFO
#
myvariable_1=toto$PLACEHOLDER1
myvariable_2=titi$PLACEHOLDER2
myvariable_final=\"dynamicvar=\${myvariable_1},\${myvariable_2}\"
EOF
"

由于 myvariable_final 未被转义并被替换为init脚本依赖项（$ remote_fs，$ syslog，$ network，$ time）

，因此效果不佳

#!/bin/bash
#
### BEGIN INIT INFO
# Provides:          my-script
# Required-Start:
# Required-Stop:
# Should-Start:
# Should-Stop:
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: blabla
# Description:       bla bla desc
#
### END INIT INFO
#
myvariable_1=totomyPlaceholder1Value
myvariable_2=titimyPlaceholder2Value
myvariable_final="dynamicvar=,"

如果我尝试将反斜杠\置于美元$后面，我设法避免替换，但我收到了不必要的反斜杠\：

export PLACEHOLDER1="myPlaceholder1Value"
export PLACEHOLDER2="myPlaceholder2Value"
sudo /bin/su -c "cat << EOF > /etc/init.d/my-script
#!/bin/bash
#
### BEGIN INIT INFO
# Provides:          my-script
# Required-Start:    \$\remote_fs \$\syslog
# Required-Stop:     \$remote_fs \$syslog
# Should-Start:      \$network \$time
# Should-Stop:       \$network \$time
# Default-Start:     2 3 4 5 
# Default-Stop:      0 1 6
# Short-Description: blabla
# Description:       bla bla desc
#
### END INIT INFO
#
myvariable_1=toto$PLACEHOLDER1
myvariable_2=titi$PLACEHOLDER2
myvariable_final=\"dynamicvar=\$\{myvariable_1},\$\{myvariable_2}\"
EOF
"

结果：

#!/bin/bash
#
### BEGIN INIT INFO
# Provides:          my-script
# Required-Start:    $\remote_fs $\syslog
# Required-Stop:
# Should-Start:
# Should-Stop:
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: blabla
# Description:       bla bla desc
#
### END INIT INFO
#
myvariable_1=totomyPlaceholder1Value
myvariable_2=titimyPlaceholder2Value
myvariable_final="dynamicvar=$\{myvariable_1},$\{myvariable_2}"

希望/出席的结果应该是：

#!/bin/bash
#
### BEGIN INIT INFO
# Provides:          my-script
# Required-Start:    $remote_fs $syslog
# Required-Stop:     $remote_fs $syslog
# Should-Start:      $network $time
# Should-Stop:       $network $time
# Default-Start:     2 3 4 5
# Default-Stop:      0 1 6
# Short-Description: blabla
# Description:       bla bla desc
#
### END INIT INFO
#
myvariable_1=totomyPlaceholder1Value
myvariable_2=titimyPlaceholder2Value
myvariable_final="dynamicvar=${myvariable_1},${myvariable_2}"

通过在 EOF 周围加上引号来解决，并在需要时使用反斜杠来控制转义

export PLACEHOLDER1="myPlaceholder1Value"
export PLACEHOLDER2="myPlaceholder2Value"
sudo /bin/su -c "cat << 'EOF' > /etc/init.d/my-script
#!/bin/bash
#
### BEGIN INIT INFO
# Provides:          my-script
# Required-Start:    \$remote_fs \$syslog
# Required-Stop:     \$remote_fs \$syslog
# Should-Start:      \$network \$time
# Should-Stop:       \$network \$time
# Default-Start:     2 3 4 5 
# Default-Stop:      0 1 6
# Short-Description: blabla
# Description:       bla bla desc
#
### END INIT INFO
#
myvariable_1=toto$PLACEHOLDER1
myvariable_2=titi$PLACEHOLDER2
myvariable_final=\"dynamicvar=\${myvariable_1},\${myvariable_2}\"
EOF
"

Answer 1

只需使用'EOF'来阻止变量扩展：

sudo /bin/su -c "cat << 'EOF' > /etc/init.d/my-script
#                       ^   ^

来自man bash：

此处文件

这种重定向指示shell从中读取输入   当前源直到一行只包含分隔符（没有   可见尾随空白）。所有读到的那一行都是   然后用作命令的标准输入。

here-documents的格式为：
      <<[-]word
              here-document
      delimiter
没有参数扩展，命令替换，算术扩展，或者对word执行路径名扩展。如果单词中有任何字符引用，分隔符是单词引用删除的结果，和 here-document中的行未展开。 如果是的话如果没有引用，here-document的所有行都会受到参数的影响扩展，命令替换和算术扩展。在里面后一种情况，字符序列\被忽略，并且必须用来引用字符\，$和`。

Answer 2

当使用su命令时，将命令本身放在sigle引号中，然后用反斜杠转义$。占位符变量必须在命令bash上下文中设置（此处为su）。所以你需要做某事......

su -c 'ph="ph"; cat << EOF > script 
varinscript=$ph
var=\${var}
EOF'

如何避免heredoc扩展变量？

2 个答案: