Linux bash string processing encyclopedia _linux Shell

Gets the length of the string

Copy Code code as follows:

Code:
%x= "ABCD"
#方法一
%expr length $x
4
# method Two
%echo ${#x}
4
# method Three
%expr "$x": ". *"
4
# Help for expr
# String:regexp anchored pattern Match of REGEXP in STRING

Find substring

Copy Code code as follows:

Code:
%expr index $x "B"
2
%expr index $x "a"
1
%expr index $x "B"
2
%expr index $x "C"
3
%EXPR index $x "D"
4

Get substring

Copy Code code as follows:

Code:
# method One
# expr <string> startpos length
%expr substr "$x" 1 3
Abc
%expr substr "$x" 1 5
Abcd
%expr substr "$x" 2 5
Bcd
# method Two
# ${x:pos:lenght}
%echo ${x:1}
Bcd
%echo ${x:2}
Cd
%echo ${x:0}
Abcd
%echo ${x:0:2}
Ab
%pos=1
%len=2
%echo ${x: $pos: $len}
Bc

Matching Regular expressions

Copy Code code as follows:

Code:
# Print Match length
%expr match $x "."
1
%expr match $x "ABC"
3
%expr match $x "BC"
0

Qiatouquwei of strings

Copy Code code as follows:

Code:
%x=aabbaarealwwvvww
%echo "${x%w*w}"
Aabbaarealwwvv
%echo "${x%%w*w}"
Aabbaareal
%echo "${x# #a *a}"
Lwwvvww
%echo "${x#a*a}"
Bbaarealwwvvww

Where, # means pinch head, because on the keyboard # on the left of $.
Where% represents% because the keyboard is on the right side of the $.
A single representation minimum match, with two representing the maximum match.
In other words, when matching a variety of scenarios, choose the maximum length of the match or the minimum length.

Substitution of strings

Copy Code code as follows:

Code:
%x=abcdabcd
%echo ${x/a/b} # replaces only one
Bbcdabcd
%echo ${x//a/b} # Replaces all
Bbcdbbcd

Can't use RegExp, can only use *? The file extension method.