如何在bash中提取子字符串

Question

我在bash中有以下字符串，长度为＆gt; 4

str = "abcdefghijklmno"

我想要提取str2 str的第一个字符str2="abcde" 。所以

{{1}}

如何用bash做到这一点？

Answer 1

请使用表达式

{string:position:length}

所以在这种情况下：

$ str="abcdefghijklm"
$ echo "${str:0:5}"
abcde

见其他用法：

$ echo "${str:0}"      # default: start from the 0th position
abcdefghijklm
$ echo "${str:1:5}"    # start from the 1th and get 5 characters
bcdef
$ echo "${str:10:1}"   # start from 10th just one character
k
$ echo "${str:5}"      # start from 5th until the end
fghijklm

取自： - wooledge.org - How can I use parameter expansion? How can I get substrings? How can I get a file without its extension, or get just a file's extension?
- Shell Command Language - 2.6.2 Parameter Expansion