Extract substrings from Shell

/** Reference address of this article: * /// Note: If I use ubuntu11.4 and run shell script sh test, an error is returned. Run/bin/bash test to obtain the correct result.

String Truncation in Shell

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 $ @ # 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