BASH Shell (string) Operation Summary

Basically, the articles referenced below add a few items to make a record, so you are too lazy to remember them, saving you the trouble of Google every time.

Http://my.oschina.net/aiguozhe/blog/41557

1. Get the length

1	STR = "ABCD"

2	Expr length $ STR #4

3	Echo $ {# STR} #4

4	Expr "$ Str ": ". *" #4

It seems that the second type is generally used.

2. Locate the substring

1	STR = "ABC"

2	Expr index $ Str "" #1

3	Expr index $ Str "B" #2

4	Expr index $ Str "X" #0

5	Expr index $ Str "" #0

3. Select substrings

1	STR = "abcdef"

2	Expr substr "$ Str" 1 3 # Take 3 characters from the first position, ABC

3	Expr substr "$ Str" 2 5 # Start from the second position and take 5 characters, bcdef

4	Expr substr "$ Str" 4 5 # Start from the fourth position with 5 characters, def

5

6	Echo $ {STR: 2} # Extract the string from the second position, bcdef

7	Echo $ {STR: 2: 3} # Extract 3 characters from the second position, BCD

8	Echo $ {STR :(-2 )} # Extract the string from the second position to the left, ABCDE

9	Echo $ {STR :(-2): 3} # Extract 6 characters from the penultimate position to the left, CDE

 

4. Capture substrings

01	STR = "abbc, def, Ghi, abcjkl"

02	Echo $ {STR # A * c} #, def, Ghi, abcjkl A well number (#) indicates the shortest matching from the left

03	Echo $ {STR # A * c} # jkl, The two pound signs (#) represent the longest match on the left.

04	Echo $ {STR # "A * C "}# Null, because STR does not contain the substring "A * C"

05	Echo $ [STR ## "A * C "}# Null. Likewise

06	Echo $ {STR # D * f) # abbc, def, Ghi, abcjkl,

07	Echo $ {STR # * D * f} #, Ghi, abcjkl

08

09	Echo $ {STR % A * l} # A percent sign (%) for abbc, def, and Ghi indicates the shortest match is intercepted from the right side.

10	Echo $ {STR % B * l} # A two percentage signs (%) indicates the longest matching from the right side

11	Echo $ {STR % A * c} # Abbc, def, Ghi, abcjkl

It can be remembered that the pound sign (#) is usually used to represent a number, which is placed in front; The percent sign (%) is unmounted to the back of the number;
Or in this way, in the keyboard layout, the well number (#) is always on the left of the percent sign (%) (that is, the Front ):-)

5. String replacement

1	STR = "Apple, tree, apple tree"

2	Echo $ {str/Apple} # Replace the first Apple

3	Echo $ {STR // Apple/Apple} # Replace all apple

4

5	Echo $ {str/# Apple/Apple }# If the STR string starts with Apple, replace it with Apple.

6	Echo $ {str/% Apple/Apple} # If the string STR ends with Apple, replace it with apple

 

6. Comparison

* A single group [] is acceptable.

1	[["A.txt" = A *] # Pattern matching)

2	[["A.txt" = ~ . * \. Txt] # RegEx matching)

3	[["ABC" = "ABC"] # Logical truth (string comparision)

4	[["11" < "2"] # Logical truth (string comparision), compared by ASCII Value

 

7. Connection

1	S1 = "hello"

2	S2 = "world"

3	Echo ${S1 }$ {S2 }# Of course, you can write $ S1 $ S2 in this way, but you 'd better add braces.

 

8. Save the command execution result in the variable.

1	Platform = 'uname-p'

2	Currentpath = 'pwd'

* Note that the two sides are not single quotes.

9. Split the string into an array.

1	Arguments = ($ (echo $ {x} | tr "," "\ N "))# X is the input parameter, separated by commas

10. case-insensitive Conversion

Debpackname ='Echo $2 | awk '{print tolower ($0 )}''
# Convert to lowercase

Debpackname ='Echo $2 | awk '{print toupper ($0 )}'`
# Convert to uppercase