When the ‘==’ and ‘!=’ operators are used, the string to the right of the operator is considered a pattern and matched according to the rules described below in Pattern Matching. (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 ! Character ranges. It is helpful to think of these as matching a string of characters rather than matching a word. The match is performed according to the rules described below (see Pattern Matching). Drop the double-quotes and/or the leading * … Valid character classes for the [] glob are defined by the POSIX standard: I would like to write a simple if/else that checks if a variable holds a pattern. Extended globbing as described by the bash man page: ? Linuxize. Now since "prasad" is the last word in my name is deepak prasad hence the bash pattern match is successful. 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. if [[ "my name is deepak prasad" =~ "prasad"$]]; then echo "bash regex match" else echo "bash regex nomatch" fi. The word hello does not match the text hello, world. Character Classes. Bash Pattern matching and regular expressions. This will become a more important distinction as you learn more complex patterns. 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. The pattern is expanded to produce a pattern just as in filename expansion. Syntax $ shopt -u option # Deactivate Bash's built-in 'option' $ shopt -s option # Activate Bash's built-in 'option' Remarks. Pattern matching using Bash features. 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 ? When writing Bash scripts you will often need to compare two strings to check if they are equal or not. In a pattern, most characters match themselves, and only themselves. So when you include double-quotes in the pattern, bash expects to see them in the filename. Pattern-matching basics . If followed by a slash /, it will match only directories and subdirectories. You can use it for manipulating and expanding variables on demands without using external commands such as perl, python, sed or awk. 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. Pattern matching in BASH. 4.3.1. The Match All Wildcard *. From the bash docs it seems you can check if it equals (=) or not (!=), but not if it contains a pattern. This guide shows you how to use parameter expansion modifiers to transform Bash shell variables for your scripting needs. Here we use =~ instead of == to match a pattern and dollar $ sign to match the last word of the string. The word hello is a perfectly valid pattern; it matches the word hello, and nothing else. T he $ character is used for parameter expansion, arithmetic expansion and command substitution. Code: Parameter is expanded and the longest match of pattern against its value is replaced with string. ... Use the == operator with the [[command for pattern matching. 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. Patterns that exactly specify the characters to be matched are called “literals” because they match the pattern literally, character-for-character. Two strings are equal when they have the same length and contain the same sequence of characters. A pattern that matches only part of a string is not considered to have matched that string. Certainly, the most widely used wildcard is the asterisk *.It will match any strings, including the null string. For example, here's how I would write it in perl.

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