shell script脚本不同执行方式结果不同，求教
脚本内容如下：
echo "$PATH\n"
echo "I love U."
echo "I Miss U"
第一种执行方式及结果：
root@sophie:/usr/bin# lily.sh
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin\n
I love U.
I Miss U
第二种执行方式及结果：
root@sophie:/usr/bin# sh lily.sh
/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
I love U.
I Miss U
求大鸟解答。
[解决办法]
echo 和 echo -e 的区别？
[解决办法]
估计你用sh lily.sh调的话是直接用sh解析的。用lily.sh直接运行的话，调的是/bin/bash
应该是这个差别导致的。你可以在脚本第一行加一句：echo $BASH确认一下。
你可以分别试用如下方法调用看区别：
sh lily.sh
./lily.sh
bash ./lily.sh
我记得在一本书里看过，说是直接用sh调用不建议。另外，脚本开头一般要明确指定用哪个shell调用，你可以在脚本第一行分别加如下语句看看区别：
#!/bin/bash
#!/bin/sh
[解决办法]
其实答案也很简单， 就是不同shell的echo实现不一样 （注意 这里的 echo 是内置命令）
$sh
$echo "test\n"
test
$bash
$ echo "test\n"
test\n
$
man page 清楚的写明了echo的用法不同
$man sh
DASH(1) BSD General Commands Manual DASH(1)
NAME
dash — command interpreter (shell)
...
echo [-n] args...
Print the arguments on the standard output, separated by spaces. Unless the -n option is present, a new‐
line is output following the arguments.
If any of the following sequences of characters is encountered during output, the sequence is not output.
Instead, the specified action is performed:
\b A backspace character is output.
\c Subsequent output is suppressed. This is normally used at the end of the last argument to sup‐
press the trailing newline that echo would otherwise output.
\f Output a form feed.
\n Output a newline character.
\r Output a carriage return.
\t Output a (horizontal) tab character.
\v Output a vertical tab.
\0digits
Output the character whose value is given by zero to three octal digits. If there are zero dig‐
its, a nul character is output.
\\ Output a backslash.
All other backslash sequences elicit undefined behaviour.
同样的对于bash
$man bash
BASH(1) BASH(1)
NAME
bash - GNU Bourne-Again SHell
...
echo [-neE] [arg ...]
Output the args, separated by spaces, followed by a newline. The return status is always 0. If -n is
specified, the trailing newline is suppressed. If the -e option is given, interpretation of the follow‐
ing backslash-escaped characters is enabled. The -E option disables the interpretation of these escape
characters, even on systems where they are interpreted by default. The xpg_echo shell option may be
used to dynamically determine whether or not echo expands these escape characters by default. echo does
not interpret -- to mean the end of options. echo interprets the following escape sequences:
\a alert (bell)
\b backspace
\c suppress further output
\e
\E an escape character
\f form feed
\n new line
\r carriage return
\t horizontal tab
\v vertical tab
\\ backslash
\0nnn the eight-bit character whose value is the octal value nnn (zero to three octal digits)
\xHH the eight-bit character whose value is the hexadecimal value HH (one or two hex digits)
\uHHHH the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHH (one to four hex
digits)
\UHHHHHHHH
the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHHHHHH (one to eight
hex digits)
如果不使用内置命令，那么你就可以看到同样的输出
$which echo
/bin/echo
$sh
$/bin/echo "test\n"
test\n
$bash
$/bin/echo "test\n"
test\n
$
此处echo 为linux coreutils 的实现
