In this article, we will learn how to find all files in a directory based on wildcard matching in Linux.
Table Of Contents
Introduction
Sometime we will get a requirement to find all the files that starts with specific text or ends with specific extension. In that case we will get the files using wildcard matching.
Wildcards are just the special characters or symbols. You can use those wildcards with any command. There are three main wildcards in Linux.
- (*) match the occurrences of one or more characters.
- (?) match the single occurrence of any character
- ([]) match the occurrence of any character which are in those square brackets. In that braces you can give any thing like symbols,alphanumerics.
Syntax :
find [-H] [-L] [-P] [-Olevel] [starting-point...] [expression]
-Olevel: Enables query for optimization.
- O1 – This is the default optimization level
- O2 – Filters the file name and next the file type
- O3 – Reorder the search automatically base don resources
Finding files based on wildcard matching
Lets create a directory with users and inside files in it. Some empty files in it.
Example 1: Search for a file with specific Filename
find -P O1 ./users -name test.json
The above example check in the folder named test and looks for the specific file named test.json. It will search recursively and prints the path of it.
Output:
./testactivate/test.json ./testactivate/routes/test.json
Example 2: Search for a file with specific pattern
find ./test -name *.json
The above example check in the folder named test and looks for the specific file with the extension as .json. It will search recursively and prints the path of it.
Output :
./testactivate/test.json ./testactivate/routes/test.json ./testactivate/routes/test2.json
Example 3: Search for a file with pattern
find . -name "??st*.json"
The above command will check filenames prefixed with any two characters followed by st but ending with one or more occurrence of any character.
Output :
./test.json ./testactivate/test.json ./testactivate/routes/pest.json ./testactivate/routes/rest2.json
Let’s see an another example,
find . -name "[pac]??[k]*"
The above command will check filename starting with [pac] any of these characters followed by any thing for next 2 characters later on [k] and lastly any occurrences.
Output :
./pend/package.json
Example 4: You can Negate the pattern using ^.
find . -name "[^pc]amp*"
The above command will check filename not to start with [pc] any of these characters followed by amp and lastly any occurrences.
Output :
./sample
Normally wildcard matching is case sensitive means abc will not match Abc or aBc. If we want to match both upper and lower case letters in names, then we include both characters in []. For example if we want to match abc and Abc then use the wildcard pattern [aA]bc*.
Finding files based on extended patterns in wildcard matching
Along with the wildcard patterns that come out of the box with most of the linux operating systems, bash allows us to use some additional patterns. We can enable those using below option
shopt -s extglob
After enabling we can use the below patterns
- ?(pattern): Match up to one occurrence of the pattern
- *(pattern): Match any number of occurrences of the pattern
- +(pattern): Match at least one occurrence of the pattern
- @(pattern): Match exactly one occurrence of the pattern
- !(pattern): Match everything except the pattern
Lets looks different examples on using these extended patterns
Example: 1
If we want to display all pdf files in a directory that has zero or one occurrence of “a”, then we can use the below command
ls ?(a).pdf
Output :
a.pdf .pdf
Example: 2
If we want to display all pdf files in a directory that has zero or more occurrence of “a”, then we can use the below command
ls *(a).pdf
Output :
aaa.pdf aa.pdf a.pdf .pdf
Example: 3
If we want to display all pdf files in a directory that has one or more occurrence of “a”, then we can use the below command
ls +(a).pdf
Output :
aaa.pdf aa.pdf a.pdf
Example: 4
If we want to display all pdf files in a directory that has only one occurrence of “a”, then we can use the below command
ls @(a).pdf
Output :
a.pdf
Finding files based on patterns
We can also specify a range of characters using square brackets. This will help us to find all files matching that pattern. Lets look at some of the patterns that we can use.
- [[:alnum:]] – Matches any alphanumeric character
- [[:space:]] – Matches any whitespace character
- [![:space:]] – Matches any character that is not whitespace
- [[:digit:]] – Matches any digit.
Lets look at one of the example to find all files that contains numbers in the filename.
ls [[:digit:]].pdf
Output :
1.pdf
Summary
That’s all for now. We learnt about finding files in a directory that matches the wildcard pattern. Thanks.