原创 Linux shell控制台改变显示前缀

同样是linux，为什么shell登录后显示的前缀会不同呢，有些显示包含当前的用户名、主机名等信息，而有些仅显示一个#，如下图：

其实，shell登陆后具体显示的内容由环境变量”PS1″控制，我们可以

echo $PS1

查看一下当前的”PS1″环境变量的内容

通过修改用户的“home”目录下的.bashrc配置文件，添加内容

export PS1=”\u@\h \w> ”

或修改全局配置文件”/etc/profile”

具体的配置内容见这篇文章：

http://www.thegeekstuff.com/2008/09/bash-shell-ps1-10-examples-to-make-your-linux-prompt-like-angelina-jolie/

1. Display username, hostname and current working directory in the prompt

The PS1 in this example displays the following three information in the prompt:

• \u – Username
• \h – Hostname
• \w – Full path of the current working directory

-bash-3.2$ export PS1="\u@\h \w> "

ramesh@dev-db ~> cd /etc/mail
ramesh@dev-db /etc/mail>

2. Display current time in the prompt

In the PS1 environment variable, you can directly execute any Linux command, by specifying in the format $(linux_command). In the following example, the command $(date) is executed to display the current time inside the prompt.

ramesh@dev-db ~> export PS1="\u@\h [\$(date +%k:%M:%S)]> "

ramesh@dev-db [11:09:56]>

You can also use \t to display the current time in the hh:mm:ss format as shown below:

ramesh@dev-db ~> export PS1="\u@\h [\t]> "
ramesh@dev-db [12:42:55]>

You can also use \@ to display the current time in 12-hour am/pm format as shown below:

ramesh@dev-db ~> export PS1="[\@] \u@\h> "
[04:12 PM] ramesh@dev-db>

3. Display output of any Linux command in the prompt

You can display output of any Linux command in the prompt. The following example displays three items separated by | (pipe) in the command prompt:

• \!: The history number of the command
• \h: hostname
  
• $kernel_version: The output of the uname -r command from $kernel_version variable
• \$?: Status of the last command

ramesh@dev-db ~> kernel_version=$(uname -r)
ramesh@dev-db ~> export PS1="\!|\h|$kernel_version|\$?> "
473|dev-db|2.6.25-14.fc9.i686|0>

4. Change foreground color of the prompt

Display prompt in blue color, along with username, host and current directory information

$ export PS1="\e[0;34m\u@\h \w> \e[m"
[Note: This is for light blue prompt]

$ export PS1="\e[1;34m\u@\h \w> \e[m"
[Note: This is for dark blue prompt]

• \e[ – Indicates the beginning of color prompt
• x;ym – Indicates color code. Use the color code values mentioned below.
• \e[m – indicates the end of color prompt

Color Code Table:

Black 0;30
Blue 0;34
Green 0;32
Cyan 0;36
Red 0;31
Purple 0;35
Brown 0;33
[Note: Replace 0 with 1 for dark color]

Make the color change permanent by adding the following lines to .bash_profile or .bashrc

STARTCOLOR='\e[0;34m';
ENDCOLOR="\e[0m"
export PS1="$STARTCOLOR\u@\h \w> $ENDCOLOR"

5. Change background color of the prompt

Change the background color by specifying \e[{code}m in the PS1 prompt as shown below.

$ export PS1="\e[47m\u@\h \w> \e[m"
[Note: This is for Light Gray background]

Combination of background and foreground

export PS1="\e[0;34m\e[47m\u@\h \w> \e[m"
[Note: This is for Light Blue foreground and Light Gray background]

Add the following to the .bash_profile or .bashrc to make the above background and foreground color permanent.

STARTFGCOLOR='\e[0;34m';
STARTBGCOLOR="\e[47m"
ENDCOLOR="\e[0m"
export PS1="$STARTFGCOLOR$STARTBGCOLOR\u@\h \w> $ENDCOLOR"

Play around by using the following background color and choose the one that suites your taste:

• \e[40m
• \e[41m
• \e[42m
• \e[43m
• \e[44m
• \e[45m
• \e[46m
• \e[47m

6. Display multiple colors in the prompt

You can also display multiple colors in the same prompt. Add the following function to .bash_profile

function prompt {
  local BLUE="\[\033[0;34m\]"
  local DARK_BLUE="\[\033[1;34m\]"
  l