Wildcards and Globbing Patterns in Bash
Wildcards and globbing patterns are powerful tools in bash for manipulating filenames and paths in a concise and flexible way. They allow you to match multiple files or directories with a single pattern instead of listing them individually. This can save you time and effort, especially when dealing with large numbers of files.
Wildcards
- * (asterisk): Matches any number of characters, including zero, in a filename or directory name.
- ? (question mark): Matches any single character in a filename or directory name.
- [] (square brackets): Defines a character class, matching any single character within the brackets.
Globbing Patterns
Combinations of wildcards and other characters to form complex matching patterns.
- *.txt: Matches all files with the ".txt" extension.
- report-*: Matches all files beginning with "report-".
- data_[0-9]*.csv: Matches all CSV files where the filename starts with "data_", followed by a single digit, and ends with ".csv".
Here are some commonly used wildcards and globbing patterns:
* (asterisk)
Matches any sequence of characters (including an empty sequence). For example, *.txt will match all files with a .txt extension in the current directory.
? (question mark)
Matches any single character. For example, file?.txt will match files like file1.txt, fileA.txt, etc.
[ ] (brackets)
Matches any single character within the specified range or set. For example, file[1-3].txt will match file1.txt, file2.txt, and file3.txt.
You can also use characters separated by commas to define a set, like file[abc].txt.
[! ] or [^ ]
Matches any single character not in the specified range or set. For example, file[!23].txt will match files that do not have 2 or 3 in the specified position.
** (double asterisk)
Matches directories and subdirectories recursively. For example, dir/**/*.txt will match all .txt files in dir and its subdirectories.
{ } (curly braces)
Matches any one of the comma-separated patterns inside the braces. For example, file{1,2}.txt will match both file1.txt and file2.txt.
This can be especially useful for generating sequences, like file{1..5}.txt.
These wildcards and globbing patterns are interpreted by the shell and are used in commands such as ls, cp, mv, and others. They allow for flexible and powerful file selection based on patterns rather than specifying each file individually.
Benefits of using wildcards and globbing patterns:
- Conciseness: Avoid long lists of filenames.
- Flexibility: Match various files with a single pattern.
- Power: Combine wildcards and operators for complex matching.
- Efficiency: Automate tasks involving multiple files.
Conclusion
Wildcards and globbing patterns in Bash are special characters that help match multiple files based on specified patterns. Common wildcards include * (matches any characters), ? (matches any single character), and [ ] (matches a range or set of characters), providing a flexible way to select and operate on groups of files in the command line.