Brief Analysis of Operation strings

An analysis of the number of string operations supported by Bash is surprising. unfortunately, these tools lack unified standards. some are the subset of parameter replacement, while others are affected by the UNIXexpr command. this leads to inconsistent command syntax and causes... brief analysis on the number of string operations supported by Bash is surprising. unfortunately, these tools lack unified standards. some are subset of parameter replacement, while others are affected by the UNIX expr command. this leads to inconsistent command syntax and redundant functions, but these are not confusing. method to obtain the string length: 1 $ {# string} 2 expr length $ string 3 expr "$ string ":'. * 'root @ ubuntu :~ /Resource/shell-study/0507-2013 # string = "abcdefg" root @ ubuntu :~ /Resource/shell-study/0507-2013 # echo $ {# string} 7 root @ ubuntu :~ /Resource/shell-study/0507-2013 # echo 'expr length $ string' 7 root @ ubuntu :~ /Resource/shell-study/0507-2013 # echo 'expr "$ string": '. *' 7 root @ ubuntu :~ /Resource/shell-study/0507-2013 # How to Learn: Insert blank lines between paragraphs in a text file #! /Bin/bash MINLEN = 3 while read line do echo "$ line" len =$ {# line} if ["$ len"-lt "$ MINLEN"]; then echo fi done exit 0 Result: root @ ubuntu :~ /Resource/shell-study/0507-2013 #./test6.sh