问题

I will only translate the non-code part of your text:

感谢Charles Duffy在评论中提供了宝贵的反馈。原始问题出现在项目1的背景下。但根据反馈，似乎项目2是更好的选项来管理系统管理任务。我可能会在完成对perl和/etc/profile.d的研究后，开另一个问题，或者在此回答中发布一些信息。

1. 原始问题：如何使用sed、awk或perl在文件中搜索和替换文字字符串，例如.bashrc文件中的PS1=<string>？
2. 更好的问题：如何使用存储在/etc/profile.d中的脚本来启用所需的提示行为，这些脚本在用户登录时自动执行？

目标是在Debian PC和DietPi（ARM）Linux系统上自动化自定义的bash提示。自定义提示在命令和终端输出之间插入一个空白行，如下所示，但颜色不同：

root@dpiBox /root
#

user@dpiBox /home/user
$

其中，root@dpiBox是红色的，user@dpiBox是绿色的，当前工作目录始终以蓝色显示。

当创建新的user时，会将/etc/skel/.bashrc的副本放置在用户的家目录中，命名为/home/user/.bashrc。root用户已经有一个副本，命名为/root/.bashrc。

我的原始计划是在添加新用户之前通过脚本编辑/etc/skel/.bashrc，并手动编辑/root/.bashrc。但是当root或任何用户登录时，这些脚本会自动在/etc/profile.d下正确执行。Charles Duffy似乎建议使用这个功能来更好地管理系统管理挑战！

默认/etc/skel/.bashrc、/root/.bashrc和/home/user/.bashrc中的相关行：

# /root/bashtest（模拟默认的.bashrc）
# /etc/skel/.bashrc
# /root/.bashrc
# /home/user/.bashrc

#force_color_prompt=yes

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[3[01;32m\]\u@\h\[3[00m\]:\[3[01;34m\]\w\[3[00m\]$ '
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w$ '
fi

步骤1 - 取消注释以打开彩色提示的行：

force_color_prompt=yes

步骤2 - 用新的PS1（在此处显示）替换旧的PS1：

PS1='${debian_chroot:+($debian_chroot)}\n\[3[01;32m\]\u@\h\[3[00m\]\[3[01;34m\] $(pwd -P) \[3[00m\]\n$ '

[01;32m\]代码是/home/user/.bashrc的绿色。将此代码更改为[01;31m\]，这是/root/.bashrc的红色。

步骤1 - sed：好结果

/usr/local/bin/bashsed（用于编辑bashtest/.bashrc的开发脚本）

#!/bin/bash
# 取消注释以强制启用彩色提示
off="#force_color_prompt=yes"
on="force_color_prompt=yes"
sed -i "s|$off|$on|" /root/bashtest

sed代码可以使用双引号或单引号来定义on和off。在sed命令中必须使用双引号。

步骤1 - perl：好结果

/usr/local/bin/bashperl（用于编辑bashtest/.bashrc的开发脚本）

#!/bin/bash
# 取消注释以强制启用彩色提示
perl -i.bak -pe 's/#force_color_prompt=yes/force_color_prompt=yes/' /root/bashtest

i.bak开关将/root/bashtest备份为/root/bashtest.bak，然后在原地编辑该文件。此命令也可以在命令行上使用，而无需使用i.bak开关。

步骤2 - sed：sed -i "s|$old|$new|" /root/bashtest的结果不好

/usr/local/bin/bashsed（用于编辑bashtest/.bashrc的开发脚本）

#!/bin/bash
# 用新的PS1替换旧的PS1
# 旧的                                    \[3[01;32m\]\u@\h\[3[00m\]:\[3[01;34m\]\w\[3[00m\]\
# PS1='${debian_chroot:+($debian_chroot)}\[3[01;32m\]\u@\h\[3[00m\]:\[3[01;34m\]\w\[3[00m\]$ '

old='\\[\3\[01;32m\\]\\u@\\h\\[\3\[00m\\]:\\[\3\[01;34m\\]\\w\\[\3\[00m\\]\\'

# 新的                                    \n\[3[01;32m\]\u@\h\[3[00m\]\[3[01;34m\] $(pwd -P) \[3[00m\]\n\
# PS1='${debian_chroot:+($debian_chroot)}\n\[3[01;32m\]\u@\h\[3[00m\]\[3[01;34m\] $(pwd -P) \[3[00m\]\n$ '

new='\\n\\[\3\[

<details>
<summary>英文:</summary>

**Edit - 06/08/23 - Original Question Kept Substantially the Same**

Thanks to Charles Duffy for providing valuable feedback in comments. The original question occurs in the context of item 1. But based on the feedback it appears that item 2 is the better option for managing system administration tasks. I may open another question or perhaps post some information in my answer here when I finish my research into ```perl``` and ```/etc/profile.d```.

1. Original Question: How to search and replace literal strings in a file, such as ```PS1=&lt;string&gt;``` in a ```.bashrc``` file, using ```sed```, ```awk```, or ```perl```?
2. Better question: How to enable desired prompt behavior using script(s) stored in ```/etc/profile.d``` that automatically execute whenever a user logs in?

Goal is to automate custom bash prompt on Debian PC and DietPi (ARM) Linux systems. The custom prompt inserts a blank line, to separate commands from terminal output, and looks like this but with different colors:

root@dpiBox /root

user@dpiBox /home/user
$

where root@dpiBox is red; user@dpiBox is green; and the present working directory is always shown in blue.

When a new ```user``` is created then a copy of ```/etc/skel/.bashrc``` is placed in the user's home directory as ```/home/user/.bashrc```. The root user already has a copy made as ```/root/.bashrc```.

My original plan was to edit ```/etc/skel/.bashrc``` via script before adding new users and to manually edit the ```/root/.bashrc```. But when root or any user log in this automatically executes scripts properly installed under ```/etc/profile.d```. Charles Duffy seems to be advising the use of this feature for better management of system administration challenges!

Relevant lines in default ```/etc/skel/.bashrc``` and ```/root/.bashrc``` and ```/home/user/.bashrc```

/root/bashtest (simulates default .bashrc)

/etc/skel/.bashrc

/root/.bashrc

/home/user/.bashrc

#force_color_prompt=yes

if [ "$color_prompt" = yes ]; then
PS1='${debian_chroot:+($debian_chroot)}[\033[01;32m]\u@\h[\033[00m]:[\033[01;34m]\w[\033[00m]$ '
else
PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w$ '
fi

Step 1 - Uncomment line to turn on color prompt:

force_color_prompt=yes

Step 2 - Replace old PS1 (above) with new PS1 (shown here) to customize bash prompt:

PS1='${debian_chroot:+($debian_chroot)}\n[\033[01;32m]\u@\h[\033[00m][\033[01;34m] $(pwd -P) [\033[00m]\n$ '

The code ```[01;32m\]``` is green for ```/home/user/.bashrc```. Change this code to ```[01;31m\]``` which is red for ```/root/.bashrc```.

**Step 1 - sed:** good result

/usr/local/bin/bashsed (development script to edit bashtest/.bashrc)

#!/bin/bash

uncomment to force color prompt on

off="#force_color_prompt=yes"
on="force_color_prompt=yes"
sed -i "s|$off|$on|" /root/bashtest

```sed``` code works with double quotes or single quotes used to define ```on``` and ```off```. The double quotes must be used in the sed command.

**Step 1 - perl:** good result 

/usr/local/bin/bashperl (development script to edit bashtest/.bashrc)

#!/bin/bash

uncomment to force color prompt on

perl -i.bak -pe 's/#force_color_prompt=yes/force_color_prompt=yes/' /root/bashtest

The ```i.bak``` switch backs up ```/root/bashtest``` as ```/root/bashtest.bak``` then edits the file in place. This command can be used on the command line without using the ```i.bak``` switch.

**Step 2 - sed:** Bad result for ```sed -i "s|$old|$new|" /root/bashtest```

/usr/local/bin/bashsed (development script to edit bashtest/.bashrc)

#!/bin/bash

replace old PS1 with new PS1

old [\033[01;32m]\u@\h[\033[00m]:[\033[01;34m]\w[\033[00m]\

PS1='${debian_chroot:+($debian_chroot)}[\033[01;32m]\u@\h[\033[00m]:[\033[01;34m]\w[\033[00m]$ '

old='\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\'

new \n[\033[01;32m]\u@\h[\033[00m][\033[01;34m] $(pwd -P) [\033[00m]\n\

PS1='${debian_chroot:+($debian_chroot)}\n[\033[01;32m]\u@\h[\033[00m][\033[01;34m] $(pwd -P) [\033[00m]\n$ '

new='\n\[\033[01;32m\]\u@\h\[\033[00m\]\[\033[01;34m\] $(pwd -P) \[\033[00m\]\n\'

sed -i "s|$old|$new|" /root/bashtest

Step 2 the code runs without error, but produces **no results**, when double quotes are used to define ```old``` and ```new```. The code throws an error ```sed: -e expression #1, char 149: unterminated `s' command``` when single quotes are used to define ```old``` and ```new```.

**Edit - 06/08/23 - Comments**

Posted my solution to **Step 2** using ```perl``` call in a ```bash``` script.

Based on feedback from Charles Duffy the ```perl``` solution for **Step 2** can be modified to use literal strings stored as bash environment variables. Relevant information is provided near the top of the page under this link:

https://mywiki.wooledge.org/BashFAQ/021

According to Charles Duffy scripts should run from ```/etc/profile.d``` when a user logs in to better manage sysadmin tasks. I need to do more research to understand this feedback. Here are two links that might be helpful:

https://serverfault.com/questions/434321/when-are-scripts-inside-etc-profile-d-executed

https://unix.stackexchange.com/questions/64258/what-do-the-scripts-in-etc-profile-d-do

**Links in Original Question**

I have searched extensively, tried dozens of experiments in the context below, and I cannot make sense of these references:

https://linuxhint.com/replace_string_in_file_bash/

https://stackoverflow.com/questions/55540596/why-would-sed-have-trouble-seeing-my-ps1-prompt

https://stackoverflow.com/questions/54599967/replacement-of-ps1-variable-in-bashrc-using-sed-or-perl

https://stackoverflow.com/questions/18376870/regarding-sed-expression-evaluation-in-shell

So I need to have my "sed" examined! I would not mind using awk if it does the job, but then I need to see the simple command structure, before inserting the literal strings. Otherwise I always mess up the syntax.

</details>


# 答案1
**得分**: 1

使用```perl```而不是```sed```或```awk```解决的。主要依赖以下参考文档：

https://www.perl.com/pub/2004/08/09/commandline.html/

```old```在PS1中的文本：

[\033[01;32m]\u@\h[\033[00m]:[\033[01;34m]\w[\033[00m]\

```perl```匹配的转义后的```old```文本：

\[\033[01;32m\]\u@\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\

```new```在PS1中的文本：

\n[\033[01;32m]\u@\h[\033[00m][\033[01;34m] $(pwd -P) [\033[00m]\n\

```perl```替换操作的转义后的```new```文本：

\n\[\033[01;32m\]\u@\h\[\033[00m\]\[\033[01;34m\] $(pwd -P) \[\033[00m\]\n\

用于调试字面字符串的转义序列的命令行模式：

```perl 's/old/DummyString/' < ps1old > ps1out; cat ps1out

这种方法通过在占位符old和占位符new表示的字面字符串上从左到右测试转义序列模式，并将结果写入文件ps1out来调试。当转义序列失败时，文件ps1old或文件ps1new保持不变；文件ps1out恢复为相应输入文件的副本；perl提供有用的调试信息。当转义序列成功时，文件ps1out显示了“DummyString”作为old或new的部分替代，从左到右逐步调试转义模式以系统地隔离语法错误。

在调试占位符old和new的字面字符串后，将工作结果传输到带有perl调用的bash脚本中，如下所示。

一个改进可能是将更改写入新文件，然后将其移动到目标.bashrc并保留.bashrc.bak作为备份。

如果此脚本运行多次，它将用编辑后的版本覆盖备份副本！

Bash脚本调用perl

#!/bin/bash

# 命令行测试将结果写入ps1out而不更改ps1old
# perl -pe 's/#force_color_prompt=yes/force_color_prompt=yes/' < ps1old > ps1out; cat ps1out

# 命令行测试将结果写入ps1out而不更改ps1old
# perl -pe 's/\\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]:\\\[\3\[01;34m\\]\\w\\\[\3\[00m\\]\\/\\n\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]\\\[\3\[01;34m\\] $\(pwd -P\) \\[\3\[00m\\]\\n\\/' < ps1old > ps1old; cat ps1out

# 如果脚本运行两次或更多次，它将覆盖以前的.bashrc.bak！
# 使用-i.bak开关备份目标.bashrc，以在原地取消注释文件！
perl -i.bak -pe 's/#force_color_prompt=yes/force_color_prompt=yes/' .bashrc

# 在测试PS1转义模式后，将旧的PS1替换为新的PS1
perl -i -pe 's/\\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]:\\\[\3\[01;34m\\]\\w\\\[\3\[00m\\]\\/\\n\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]\\\[\3\[01;34m\\] $\(pwd -P\) \\[\3\[00m\\]\\n\\/' .bashrc

\[3[01;32m\]\u@\h\[3[00m\]:\[3[01;34m\]\w\[3[00m\]\

\\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]:\\\[\3\[01;34m\\]\\w\\\[\3\[00m\\]\\

\n\[3[01;32m\]\u@\h\[3[00m\]\[3[01;34m\] $(pwd -P) \[3[00m\]\n\

\\n\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]\\\[\3\[01;34m\\] $\(pwd -P\) \\[\3\[00m\\]\\n\\

perl 's/old/DummyString/' < ps1old > ps1out; cat ps1out

# ~/ps1old

#force_color_prompt=yes

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\[3[01;32m\]\u@\h\[3[00m\]:\[3[01;34m\]\w\[3[00m\]$ '
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w$ '
fi

perl 's/new/DummyString/' < ps1new > ps1out; cat ps1out

# ~/ps1new

#force_color_prompt=yes

if [ "$color_prompt" = yes ]; then
    PS1='${debian_chroot:+($debian_chroot)}\n\[3[01;32m\]\u@\h\[3[00m\]\[3[01;34m\] $(pwd -P) \[3[00m\]\n$ '
else
    PS1='${debian_chroot:+($debian_chroot)}\u@\h:\w$ '
fi

perl 's/old/new/' < ps1old > ps1out; cat ps1out

perl -pe 's/\\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]:\\\[\3\[01;34m\\]\\w\\\[\3\[00m\\]\\/\\n\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]\\\[\3\[01;34m\\] $\(pwd -P\) \\[\3\[00m\\]\\n\\/' < ps1old > ps1old; cat ps1out

#!/bin/bash

# Command line test writes result to ps1out without changing ps1old
# perl -pe 's/#force_color_prompt=yes/force_color_prompt=yes/' < ps1old > ps1out; cat ps1out

# Command line test writes result to ps1out without changing ps1old
# perl -pe 's/\\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]:\\\[\3\[01;34m\\]\\w\\\[\3\[00m\\]\\/\\n\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]\\\[\3\[01;34m\\] $\(pwd -P\) \\[\3\[00m\\]\\n\\/' < ps1old > ps1old; cat ps1out

# If script is run two or more times it overwrites previous .bashrc.bak!
# Backup target .bashrc using -i.bak switch to uncomment file in place!
perl -i.bak -pe 's/#force_color_prompt=yes/force_color_prompt=yes/' .bashrc

# Replace old PS1 with new PS1 after testing PS1 escape pattern on command line
perl -i -pe 's/\\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]:\\\[\3\[01;34m\\]\\w\\\[\3\[00m\\]\\/\\n\\[\3\[01;32m\\]\\u@\\h\\\[\3\[00m\\]\\\[\3\[01;34m\\] $\(pwd -P\) \\[\3\[00m\\]\\n\\/' .bashrc