在 sed 命令语法中调用变量 [重复]答案

【问题标题】：Calling variable within sed command syntax [duplicate]在 sed 命令语法中调用变量 [重复]
【发布时间】：2019-06-24 09:10:56
【问题描述】：

我正在创建一个脚本，以便让我的组织更轻松地将工作站添加到我们的 Nagios 监控系统。

每次脚本运行时，我都希望能够输入主机名、别名和地址（作为用户输入的变量），并在 sed 命令中调用这些变量，以便“创建”一个新的主机速度要快得多，然后全部输入。

我正在尝试在 sed 找到之后添加整个字符串 "主机地址}"

我认为是 /a （在找到所述字符串后追加）尽管如此，使用双引号仍然不允许调用变量。

#!bin/bash

# Prompt for hostname, alias, and IP address of new host
# take user input has variable to be used in sed 

# Takes user input for hostname
echo host_name : 
read var_hostname    
# Takes user input for alias
echo alias : 
read var_alias
# Takes user input for ip address
echo address : 
read var_address
# searches for the top-most instance "address of the host" within the     windows.cfg file
# after said instance is found, appends the new string below, which calls     for the variables received 
# previously by user
sed -i -e  " address of the host } /a 
define host{
    use             windows-server  ; Inherit default values from a     template
    host_name       $var_hostname       ; The name we are giving to this     host
    alias           $var_alias       ; A longer name associated with the host
    address         $var_address     ; IP address of the host
    }" 
    windows.cfg

我希望将字符串“define host{}”与用户输入的变量一起写入文件中。而不是

【问题讨论】：

变量总是用双引号代替，我看不出它在这里不起作用的任何原因。如果用文字字符串替换变量是否有效？
address of the host} a 应该是/address of the host/a
我尝试使用 /option/ 但这否定了变量。现在正在调用变量......但是当我运行脚本时我收到了这个：表达式＃1，char 28：命令后的额外字符
如果你想查看 shell 脚本在做什么，请将 set -x 放在开头。然后它将显示所有正在执行的命令，并填充变量。
@Allan 是的，您的解释写得非常好，有助于澄清分配。我还按照建议完成了 -x 命令，以查看该命令实际上在做什么，这很有用。脚本运行没有错误...但 windows.cfg 文件没有变化。

标签： bash variables sed

【解决方案1】：

要修改的文件windows.cfg

 cat windows.cfg 
#some settings
#more settings
test
abc

lot of stuff

test2

backup

 address of the host }

Sed 脚本：

 cat sed.sh 
#!/bin/bash

# Prompt for hostname, alias, and IP address of new host
# take user input has variable to be used in sed

# Takes user input for hostname
echo host_name :
read var_hostname
# Takes user input for alias
echo alias :
read var_alias
# Takes user input for ip address
echo address :
read var_address
# searches for the top-most instance "address of the host" within the     windows.cfg file
# after said instance is found, appends the new string below, which calls     for the variables received
# previously by user
sed -e  '/address of the host }/r'<(
echo "define host{"
echo "   use             windows-server  ; Inherit default values from a template"
echo "   host_name       $var_hostname       ; The name we are giving to this host"
echo "   alias           $var_alias       ; A longer name associated with the host"
echo "   address         $var_address     ; IP address of the host"
echo "   }") -i -- windows.cfg

执行：

 ./sed.sh 
host_name :
allan.com
alias :
allan
address :
123.123.123.123

输出：

 cat windows.cfg 
#some settings
#more settings
test
abc

lot of stuff

test2

backup

 address of the host }
define host{
   use             windows-server  ; Inherit default values from a template
   host_name       allan.com       ; The name we are giving to this host
   alias           allan       ; A longer name associated with the host
   address         123.123.123.123     ; IP address of the host
   }

说明：

我决定不使用a，而是使用sed 中的r 命令（读取文件的内容以便插入它）。然后我使用符号<() 让sed 操作的所有echo 命令的输出就好像它是一个文件一样。这可以避免 sed 与 { 字符的歧义，这提供了更好的可读性。

进程替换：http://tldp.org/LDP/abs/html/process-sub.html

【讨论】：