Shell string processing command

Shell string processing string length [plain] shell> echo $ {# string} shell> expr length $ string shell> expr "$ string ":'. * 'www.2cto.com matches the length of the substring starting with a string [plain] expr match "$ string"' $ substring is a regular expression. expr "$ string": '$ substring' index [plain] expr index $ string $ substring extract substring [plain] $ {string: position} in $ string, the substring is extracted from position $ position. if $ string is "*" or "@", the parameter starting from position $ position is extracted. [1] $ {string: position: length} www.2cto.com
Extract the length of $ length substring from position $ position in $ string. [plain] stringZ = abcABC123ABCabc #0123456789 ..... #0-based indexing. echo $ {stringZ: 0} # abcABC123ABCabc echo $ {stringZ: 1} # bcABC123ABCabc echo $ {stringZ: 7} #23 ABCabc echo $ {stringZ: 7: 3} # 23A # The length of the extracted substring is 3.
# Can I start to extract the substring from the right (that is, the end) of the string? Echo $ {stringZ:-4} # abcABC123ABCabc # extracts the entire string by default, just like $ {parameter:-default. # however... echo $ {stringZ :(-4) }# Cabc echo $ {stringZ:-4} # Cabc note: ":" There is a space on the right! # In this way, it can work. # use parentheses or add a space to escape the parameter. if the $ string parameter is "*" or "@", $ length parameters are extracted from the $ position parameter, but because $ length parameters may not exist, then several location parameters are extracted. [plain] echo $ {*: 2} # print out 2nd and all the following location parameters. echo $ {@: 2} # Same as above. echo $ {*: 2: 3} # print three position parameters in a row starting from 2nd. www.2cto.com expr substr $ string $ position $ length in $ string, the Child string of $ length is extracted from $ position. [plain] echo 'expr substr $ stringZ 1 2 'echo 'expr substr $ stringZ 4 3 'expr match "$ string" '\ ($ substring \) 'extract $ substring from the starting position of $ string, and $ substring is a regular expression. expr "$ string": '\ ($ substring \)' extracts $ substring from the starting position of $ string, and $ substring is a regular expression.
[Plain] stringZ = abcABC123ABCabc #======= echo 'expr match "$ stringZ "'\(. [B-c] * [A-Z] .. [0-9] \) ''echo 'expr "$ stringZ ":'\(. [B-c] * [A-Z] .. [0-9] \) ''echo 'expr "$ stringZ ":'\(....... \) ''# Each echo above prints the same result. abcABC1 expr match "$ string "'. * \ ($ substring \) 'extracts $ substring from the end of $ string, and $ substring is a regular expression. expr "$ string ":'. * \ ($ substring \) 'extracts $ substring from the end of $ string, and $ substring is a regular expression.
[Plain] expr match "$ stringZ "'. * \ ([A-C] [A-C] [A-C] [a-c] * \) 'abcabc www.2cto.com expr "$ stringZ ":'. *\(...... \) 'abcabc substrings remove [plain] $ {string # substring} and cut off the minimum matching $ substring from the beginning of $ string. $ {string ## substring} removes the longest matched $ substring from the start of $ string. $ {string % substring} Cut the minimum matching $ substring from the end of $ string. $ {string % substring} truncated the longest matched $ substring from the end of $ string. echo $ {stringZ % B * c} # abcABC123ABCa # Cut off the shortest match between 'B' and 'c' from the end of $ stringZ. echo $ {stringZ % B * c} # a # removes the longest match between 'B' and 'c' from the end of $ stringZ. this operation is especially useful when you need to construct a file name. replace www.2cto.com [plain] $ {string/substring/replacement} with $ 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, $ replacement is used to replace $ substring. $ {string/% substring/replacement} If $ substring matches the end of $ string, $ replacement is used to replace $ substring [extracted from books and processed strings, familiar with the operations provided by Bash, general applications can still handle well]