Summary of 8 String Interception Methods in Shell Script
Get the path (directory) where the current shell script is located, supports soft links.
DIR=`S=\`readlink "$0"\`; [ -z "$S" ] && S=$0; dirname $S`
String truncation for Linux is useful. There are eight methods.
Suppose there is variable var=http://www.aaa.com/123.htm.
1. Intercept the # sign, delete the characters on the left, and keep the characters on the right.
echo $ {var # * //
Where var is the variable name, the # sign is the operator, *// means to delete the first // sign and all the characters on the left from the left,
that is, delete http://
and the result is: www.aaa.com/123.htm
2. The ## sign is intercepted, the characters on the left are deleted, and the characters on the right are reserved.
echo $ {var ## * /
##*/ means to delete the last (rightmost) / sign from the left and all the characters on the left to
delete http://www.aaa.com/
The result is 123.htm
3. % sign interception, delete the right character, keep the left character
echo $ {var% / *
%/* means start from the right, delete the first / sign and the characters to the right
The result is: http://www.aaa.com
4. %% sign interception, delete the characters on the right, keep the characters on the left
echo $ {var %% / *
%%/* means start from the right, delete the last (leftmost) / sign and the characters on the right. The
result is: http:
5. The first character from the left, and the number of characters
echo $ {var: 0: 5
Where 0 indicates the start of the first character on the left, and 5 indicates the total number of characters.
The result is: http:
6. 从左边第几个字符开始，一直到结束。
echo ${var:7}
其中的 7 表示左边第8个字符开始，一直到结束。
结果是 ：www.aaa.com/123.htm
7. 从右边第几个字符开始，及字符的个数
echo ${var:0-7:3}
其中的 0-7 表示右边算起第七个字符开始，3 表示字符的个数。
结果是：123
8. 从右边第几个字符开始，一直到结束。
echo ${var:0-7}
表示从右边第七个字符开始，一直到结束。
结果是：123.htm
注：（左边的第一个字符是用 0 表示，右边的第一个字符用 0-1 表示）