The word hello is a perfectly valid pattern; it matches the word hello, and nothing else. Character ranges. Note that in Bash when the globstar option is enabled, two adjacent asterisk * used as a single pattern will match all files and zero or more directories and subdirectories. Bash Pattern matching and regular expressions. Pattern-matching basics . This guide shows you how to use parameter expansion modifiers to transform Bash shell variables for your scripting needs. This will become a more important distinction as you learn more complex patterns. Pattern matching in BASH. (pattern-list) Matches zero or one occurrence of the given patterns *(pattern-list) Matches zero or more occurrences of the given patterns +(pattern-list) Matches one or more occurrences of the given patterns @(pattern-list) Matches one of the given patterns ! ... Use the == operator with the [[command for pattern matching. Syntax $ shopt -u option # Deactivate Bash's built-in 'option' $ shopt -s option # Activate Bash's built-in 'option' Remarks. Patterns that exactly specify the characters to be matched are called “literals” because they match the pattern literally, character-for-character. Code: The match is performed according to the rules described below (see Pattern Matching). Character Classes. 4.3.1. Here we use =~ instead of == to match a pattern and dollar $ sign to match the last word of the string. Certainly, the most widely used wildcard is the asterisk *.It will match any strings, including the null string. So when you include double-quotes in the pattern, bash expects to see them in the filename. Now since "prasad" is the last word in my name is deepak prasad hence the bash pattern match is successful. Drop the double-quotes and/or the leading * … Apart from grep and regular expressions, there's a good deal of pattern matching that you can do directly in the shell, without having to use an external program. The Match All Wildcard *. If you’ve been thinking about mastering Bash, do yourself a favor and read this book, which will help you take control of your Bash command line and shell scripting. Based on my Bash experience, I’ve written Bash 101 Hacks eBook that contains 101 practical examples on both Bash command line and shell scripting. Extended globbing as described by the bash man page: ? A pattern that matches only part of a string is not considered to have matched that string. Two strings are equal when they have the same length and contain the same sequence of characters. If followed by a slash /, it will match only directories and subdirectories. It is helpful to think of these as matching a string of characters rather than matching a word. Parameter is expanded and the longest match of pattern against its value is replaced with string. if [[ "my name is deepak prasad" =~ "prasad"$]]; then echo "bash regex match" else echo "bash regex nomatch" fi. The pattern is expanded to produce a pattern just as in filename expansion. Networking With Bash; Parallel; Pattern matching and regular expressions; Behaviour when a glob does not match anything; Case insensitive matching; Check if a string matches a regular expression; Extended globbing; Get captured groups from a regex match against a string; Matching hidden files; Regex matching; The * glob; The ** glob; The ? I would like to write a simple if/else that checks if a variable holds a pattern. T he $ character is used for parameter expansion, arithmetic expansion and command substitution. Valid character classes for the [] glob are defined by the POSIX standard: For example, here's how I would write it in perl. 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