Pattern matching in bash parameter substitution

Pattern matching in parameter substitution

# and # # start from the left side of the string, and remove the left string,

% and percent are started from the right side of the string, and the right substring is removed.

For example

Name=hello lhhs "Root"

name=${name# ' "'}; Name=${name% ' "'}

Result is root

############################### #Start script#######################################

1 #!/bin/bash

2 # patt-matching.sh

3

4 # use # # #% of percent to match the pattern of the parameter substitution operation.

5

6 var1=abcd12345abc6789

7 Pattern1=a*c # * (wildcard characters) matches any character between a-c.

8

9 Echo

echo "var1 = $var 1" # abcd12345abc6789

echo "var1 = ${var1}" # abcd12345abc6789

# (Alternate form)

echo "Number of characters in ${var1} = ${#var1}"

Echo

15

echo "pattern1 = $pattern 1" # A*c (Everything between ' a ' and ' C ')

echo "--------------"

Echo ' ${var1# $pattern 1} = ' ${var1# $pattern 1} ' # d12345abc6789

19 # The shortest possible match, minus the first 3 characters of the abcd12345abc6789

20 # |-| ^^^

Echo ' ${var1## $pattern 1} = ' ${var1## $pattern 1} ' # 6789

22 # The furthest match, minus the first 12 characters of the abcd12345abc6789.

# |----------| ^^^^

24

echo; Echo Echo

26

Any character between pattern2=b*9 # ' B ' to ' 9 '

echo "var1 = $var 1" # or abcd12345abc6789

Echo

echo "pattern2 = $pattern 2"

echo "--------------"

Echo ' ${var1%pattern2} = ' "${var1% $pattern 2}" # abcd12345a

33 # Recent matches, minus the last 6 characters of abcd12345abc6789

# |----| ^^^^

Echo ' ${var1%%pattern2} = ' "${var1%% $pattern 2}" # A

36 # Furthest match, minus the last 12 characters of abcd12345abc6789

Panax Notoginseng # |-------------| ^^^^^^

38

39 # Remember, # and # # Start with the left side of the string, and remove the left string,

40 #% and percent of zero start from the right side of the string and remove the right substring.

41

Echo

43

0 exit

Pattern matching in bash parameter substitution