击：如何来标记一个字符串变量？ [英] Bash: How to tokenize a string variable?

问题描述

如果我有一个字符串变量谁的值是约翰是17岁我怎么记号化这使用空格作为分隔符？我会用 AWK ？

If I have a string variable who's value is "john is 17 years old" how do I tokenize this using spaces as the delimeter? Would I use awk?

推荐答案

使用shell的变量不带引号的自动标记化：

Use the shell's automatic tokenization of unquoted variables:

$ string="john is 17 years old"
$ for word in $string; do echo "$word"; done
john
is
17
years
old

如果你想改变你可以设置 $ IFS 变量，代表内部字段分隔的分隔符。 $ IFS 的默认值为\\ t \\ n（空格，制表符，换行符）。

If you want to change the delimiter you can set the $IFS variable, which stands for internal field separator. The default value of $IFS is " \t\n" (space, tab, newline).

$ string="john_is_17_years_old"
$ (IFS='_'; for word in $string; do echo "$word"; done)
john
is
17
years
old

（注意，在我周围添加第二行括号内第二个例子中，这将创建一个子shell，这样更改为 $ IFS 不存在。您一般不希望永久更改 $ IFS ，因为它可以发泄对不知情的shell命令破坏。）

(Note that in this second example I added parentheses around the second line. This creates a sub-shell so that the change to $IFS doesn't persist. You generally don't want to permanently change $IFS as it can wreak havoc on unsuspecting shell commands.)

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