echo打印换行

shell环境中，echo是常用的数据命令，但有的时候，想通过“\n”使输出换行却换不了，这个时候需要增加-e选项：

$ echo "Hellow.\nHey man~"                                                                                                                                     
Hellow.\nHey man~
$ echo -e "Hellow.\nHey man~"                                                                                                                                  
Hellow.
Hey man~

查看echo手册：

ECHO(1)                          User Commands                         ECHO(1)

NAME
       echo - display a line of text

SYNOPSIS
       echo [SHORT-OPTION]... [STRING]...
       echo LONG-OPTION

DESCRIPTION
       Echo the STRING(s) to standard output.

       -n     do not output the trailing newline

       -e     enable interpretation of backslash escapes

       -E     disable interpretation of backslash escapes (default)

       --help display this help and exit

       --version
              output version information and exit

       If -e is in effect, the following sequences are recognized:

       \\     backslash

       \a     alert (BEL)

       \b     backspace

       \c     produce no further output

       \e     escape

       \f     form feed

       \n     new line

       \r     carriage return

       \t     horizontal tab

       \v     vertical tab

       \0NNN  byte with octal value NNN (1 to 3 digits)

       \xHH   byte with hexadecimal value HH (1 to 2 digits)

       NOTE:  your  shell  may  have  its own version of echo, which usually supersedes the version described here.  Please refer to your shell’s documentation for details
       about the options it supports.

AUTHOR
       Written by Brian Fox and Chet Ramey.

可以看到-e的作用是使带反斜杠'\'的转义符生效。因此想让\n生效，必须带上-e选项。