Bash PS1、PS2、PS3、PS4 提示符笔记

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PS1    The value of this parameter is expanded (see PROMPTING below) and used as the primary prompt string.  The default value is ``\s-\v\$ ''.
PS2    The value of this parameter is expanded as with PS1 and used as the secondary prompt string.  The default is ``> ''.
PS3    The value of this parameter is used as the prompt for the select command (see SHELL GRAMMAR above).
PS4    The value of this parameter is expanded as with PS1 and the value is printed before each command bash displays during an execution trace.  The first character of PS4 is repli‐
      cated multiple times, as necessary, to indicate multiple levels of indirection.  The default is ``+ ''.

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[root@local ~]# echo -e "\$PS1默认值: $PS1\n\$PS2默认值: $PS2\n\$PS3默认值: $PS3\n\$PS4默认值: $PS4"
$PS1默认值: [\u@\h \W]\$ 
$PS2默认值: > 
$PS3默认值: 
$PS4默认值: +