Shell string operation summary

Shell string operation summary

#! /Bin/bash

######################################## ##
#
# Demonstrate string operations in bash
#
# Output result
#
######################################## ##

STR = "abc123abcabc"
# |-|
# | ------- |

# Calculate the length of a string
Echo $ {# STR} #12

# Operations related to location parameters
Echo $ {# *} # Number of location parameters
Echo $ {## the number of location parameters is the same as the above
Echo $ * # output all location parameters as a string
Echo [email protected] # same effect as above
# String Truncation
#
# $ {String # substring}
# Remove the first matched $ substring from the first character on the left of $ string
#$ {String ## substring}
# Remove the last matched $ substring from the first character on the left of $ string
#
# Start from the left
Echo $ {STR # A * c} # minimum matching between A and C
Echo $ {STR # A * c} # maximum matching between A and C

# Start from the right
Echo $ {STR % A * c} # Start from the last character on the right to find the shortest match between A and B.
Echo $ {STR % a * B} # Find the longest match between A and B starting from the last character on the right
# The mode cannot be found.

#== Substring =
# $ {String: Position}
# $ {String: positon: length}
#
Echo $ {STR: 2} # extract the string value from the first position
Echo $ {STR: 2: 3} # extract a value with a length of 3 characters from the first position
# Reverse extraction of substrings
Echo $ {STR :(-2)} # extract the string from the first position in the reverse direction
Echo $ {STR :(-2): 6} # extract a string with a length of 6 characters from the reverse of 2nd characters (:( it is impossible)
# How to extract 6 characters with only two characters in length?
Echo $ {STR :(-6): 3} #6 medium proposed 3 Total can be

# Location Parameter Extraction

Echo $ {*: 2} # extract the values of all the following parameters from the second parameter
Echo $ {*: 2: 3} # extract the values of the three parameters from the second parameter

# = Substring replacement =
# $ {String/substring/replacement}
# Use $ replacement to replace the first matched $ substring.
# $ {String // substring/replacement}
# Use $ replacement to replace all matched $ substring.
#
# $ {String/# substring/replacement}
# If $ substring matches the starting part of $ string, replace $ substring with $ replacement.
# $ {String/% substring/replacement}
# If $ substring matches the end of $ string, replace $ substring with $ replacement.
#
Str1 = "123abcabcab12"

Echo $ {str1/12/hover} # Replace the first
Echo ${str1 // 12/hover} # Replace all

Echo $ {str1/#12/hover} # Match 12 from the beginning. If yes, replace
Echo $ {str1/% 12/hover} # Match 12 from the end. If it is found, replace

######################################## ############# 3

Assign a single string to an array:

[Email protected] ~
$ STR = abcdefg

[Email protected] ~
$ I = 0; while (I <$ {# STR}); Do array [$ I] =$ {STR: I: 1 }; (I ++); done

[Email protected] ~
$ Set | grep Array
Array = ([0] = "A" [1] = "B" [2] = "C" [3] = "D" [4] = "E" [5] = "F" [6] = "G" [7] = "")

[Email protected] ~
$ Echo $ {array [0]}
A

[Email protected] ~
$ Echo $ {array [1]}
B

[Email protected] ~
$ Echo $ {array [@]}
A B C D E F G

For index in 'seq 0 $ ($ {# STR}-1 ))'
Do
Array [$ Index] =$ {STR: $ index: 1}
Done

 

 

 

Shell String Array Processing

This code is used to process the call of a program (SCRIPT) in the system, but does not know the specific location of the program file, but only knows the possible location. A little smart.

Exp_cmds = "$ base_dir/$ old_version/bin/exp_my_db/
$ Base_dir/$ old_version/bin/exp_db/
$ Base_dir/$ version/bin/exp_db/
$ Base_dir/$ old_version/My/scripts/exp_my_db/
$ Base_dir/$ old_version/My/scripts/exp_db/
$ Base_dir/$ version/My/scripts/exp_db "# create a string array separated by symbols /.

Exp_defaults _found = 0

For CMD in $ exp_cmds # Use for to loop
Do
If [-F $ cmd] # exp_db exists or exp_my_db is the script file.
Then
Echo "exporting database ..."
Run_as_oracle_nolog $ cmd 100 $ my_backup_dir 2> & 1 | $ tee-A $ tmp_file # core program
Exp_1__found = 1
Break # Haha found one and immediately quit after the function is completed.
Fi
Done

Although Sparrow is small, it is very enlightening.