Wildcard meaning:

? Any single character * Any character of any length any character [] Single character in the specified range [:space:] : blank character [:punct:] : punctuation [:lower:] : lowercase letters [:upper:]: uppercase letters [:alpha:]: Upper and lower case letters [:digit:]: digit [:alnum:]: digit and upper and lower case letters [^] Single character outside the specified range {} Command line expansion '' command to replace $() command to replace "" weak reference, variable substitution can be implemented '' strong reference, variable substitution is not completedCopy the code

Regular expressions:

.Any single character \? Match the preceding character 0 or 1 times * Match the preceding character any time [] single character within the specified range [^] single character outside the specified range \{m,n\} Match the preceding character at least m times and at most N times ^ line header anchor $line tail anchor \< or \b word header anchor \> or \b word tail anchor \(\ Group \1 matches the contents of the previous first groupCopy the code

Extended regular expressions:

. Any single character? Matches the preceding character 0 or 1 times + matches the preceding character at least 1 times * Matches the preceding character any time [] single character within the specified range [^] Single character outside the specified range {m,n} matches the preceding character at least m times and at most n times ^ line header anchor $line tail anchor \< or \b word header anchor \> or \b terminating anchor () group \1 matches the contents of the previous first groupCopy the code