1、Example 5-2(怎么样才能显示下面这个 $escape ?)
54 escape=$'\033' # 033 is octal for escape.
55 echo "\"escape\" echoes as $escape"
56 # no visible output.
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2、echo -e的用法：
[mdx@localhost abs-exercises]$ echo "\n"
\n
[mdx@localhost abs-exercises]$ echo -e "\n"
[mdx@localhost abs-exercises]$
[mdx@localhost abs-exercises]$ echo "\\"
\
[mdx@localhost abs-exercises]$ echo -e "\\"
\
[mdx@localhost abs-exercises]$ echo -e '\\'
\
[mdx@localhost abs-exercises]$ echo '\\'
\\
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3、可是说是一些非常烦人的用法，不用去记它，平常也用不着吧。
Note The behavior of \ depends on whether it is itself escaped, quoted, or
appearing within command substitution or a here document.
1 # Simple escaping and quoting
2 echo \z # z
3 echo \\z # \z
4 echo '\z' # \z
5 echo '\\z' # \\z
6 echo "\z" # \z
7 echo "\\z" # \z
8
9 # Command substitution
10 echo `echo \z` # z
11 echo `echo \\z` # z
12 echo `echo \\\z` # \z
13 echo `echo \\\\z` # \z
14 echo `echo \\\\\\z` # \z
15 echo `echo \\\\\\\z` # \\z
16 echo `echo "\z"` # \z
17 echo `echo "\\z"` # \z
18
19 # Here document
20 cat <<EOF
21 \z
22 EOF # \z
23
24 cat <<EOF
25 \\z
26 EOF # \z
27
28 # These examples supplied by St?phane Chazelas.
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4、\可以起到续行符的作用，文中的叙述：
The escape also provides a means of writing a multi-line command. Normally,
each separate line constitutes a different command, but an escape at the end of
a line escapes the newline character, and the command sequence continues on to
the next line.
例如：下面的dir这个命令被分成3行来写，每行一个字符：）
[mdx@localhost abs-exercises]$ d\
> i\
> r
ch4-2.txt ctrl-h.sh ex2-1.sh ex2-3.sh ex4-5.sh ex4-7.sh plan2.txt
ch5-2.txt ctrl-m.sh ex2-2.sh ex4-2.sh ex4-6.sh ex5-2.sh plan.txt
[mdx@localhost abs-exercises]$ dir
ch4-2.txt ctrl-h.sh ex2-1.sh ex2-3.sh ex4-5.sh ex4-7.sh plan2.txt
ch5-2.txt ctrl-m.sh ex2-2.sh ex4-2.sh ex4-6.sh ex5-2.sh plan.txt
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