Chapter 5. Quoting

Chapter 5. Quoting

1、那个IFS是什么意思？

Example 5-1. Echoing Weird Variables

1 #!/bin/bash    2 # weirdvars.sh: Echoing weird variables.    3    4 var="'(]\\{}\$\""    5 echo $var        # '(]\{}$"    6 echo "$var"      # '(]\{}$"     Doesn't make a difference.    7    8 echo    9   10 IFS='\'   11 echo $var        # '(] {}$"     \ converted to space. Why?   12 echo "$var"      # '(]\{}$"   13   14 # Examples above supplied by Stephane Chazelas.   15   16 exit 0

2、

[mdx@localhost mdx]$ echo '\'' > > > ...

(回车就显示>，永远不会出现'，除非'没有在两个'之中)

Since even the escape character (\) gets a literal interpretation within single quotes, trying to enclose a single quote within single quotes will not yield the expected result.

1 echo "Why can't I write 's between single quotes"    2    3 echo    4    5 # The roundabout method.    6 echo 'Why can'\''t I write '"'"'s between single quotes'    7 #    |-------|  |----------|   |-----------------------|    8 # Three single-quoted strings, with escaped and quoted single quotes between.    9   10 # This example courtesy of Stéphane Chazelas.

3、太令人难以把握了，没有规律吗？

Of more concern is the inconsistent behavior of "\" within double quotes.

bash$ echo hello\!  hello!      bash$ echo "hello\!"  hello\!          bash$ echo -e x\ty  xty      bash$ echo -e "x\ty"  x       y

4、生词：

Quoting can also suppress echo's  "appetite" for newlines.

Weird

discrete