How to use Linux find command.

find Command Syntax

The general syntax for the find command is as follows:

find [options] [path...] [expression]

• The options attribute controls the treatment of the symbolic links, debugging options, and optimization method.

• The path… attribute defines the starting directory or directories where find will search the files.

• The expression attribute is made up of options, search patterns, and actions separated by operators.

To search for files in a directory, the user invoking the find command needs to have read permissions on that directory.

Let’s take a look at the following example:

find -L /var/www -name "*.js"

• The option -L (options) tells the find command to follow symbolic links.

• The /var/www (path…) specifies the directory that will be searched.

• The (expression) -name “*.js tells find to search files ending with .js (JavaScript files).

Find Files by Name

Finding files by name is probably the most common use of the find command. To find a file by its name, use the -name option followed by the name of the file you are searching for.

For example, to search for a file named document.pdf in the /home/liviu directory, you would use the following command:

find /home/liviu-test -type f -name document.pdf

To run a case-insensitive search, change the -name option with -iname:

find /home/liviu-test -type f -iname document.pdf

The command above will match “Document.pdf”, “DOCUMENT.pdf” ..etc.

Find Files by Extension

Searching for files by extension is the same as searching for files by name. For example, to find all files ending with .log.gz inside the /var/log/nginx directory, you would type:

find /var/log/nginx -type f -name '*.log.gz'

It is important to mention that you must either quote the pattern or escape the asterisk * symbol with backslash \ so that it doesn’t get interpreted by the shell when you use the wildcard character.

To find all files that don’t match the regex *.log.gz you can use the -not option. For example, to find all files that don’t end in *.log.gz you would use:

find /var/log/nginx -type f -not -name '*.log.gz'

Find Files by Type

Sometimes you might need to search for specific file types such as regular files, directories, or symlinks. In Linux, everything is a file.

To search for files based on their type, use the -type option and one of the following descriptors to specify the file type:

• f: a regular file

• d: directory

• l: symbolic link

• c: character devices

• b: block devices

• p: named pipe (FIFO)

• s: socket

For instance, to find all directories in the current working directory , you would use:

find . -type d

The common example would be to recursively change the website file permissions to 644 and directory permissions to 755 using the chmod command:

.
./.pki
./.pki/nssdb
./.gnupg
./.ssh
./nexonhost.com
./nexonhost.com/how-to-zip-files-and-directories
./nexonhost.com/bash-until-loop
./nexonhost.com/how-to-kill-a-process
./nexonhost.com/how-to-install-gitea-on-ubuntu-20-04
./nexonhost.com/how-to-use-nc-command
./nexonhost.com/colocation
./nexonhost.com/2023
............................................................................................

Find Files by Size

To find files based on the file size, pass the -size parameter along with the size criteria. You can use the following suffixes to specify the file size:

• b: 512-byte blocks (default)

• c: bytes

• w: two-byte words

• k: Kilobytes

• M: Megabytes

• G: Gigabytes

The following command will find all files of exactly 1024 bytes inside the /tmp directory:

find /tmp -type f -size 1024c

The find command also allows you to search for files that are greater or less than a specified size.

In the following example, we search for all files less than 1MB inside the current working directory. Notice the minus – symbol before the size value:

find . -type f -size -1M

If you want to search for files with a size greater than 1MB, then you need to use the plus + symbol:

find . -type f -size +1M

You can even search for files within a size range. The following command will find all files between 1 and 2MB:

find . -type f -size +1M -size 21M

Find Files by Modification Date

The find command can also search for files based on their last modification, access, or change time.

Same as when searching by size, use the plus and minus symbols for “greater than” or “less than”.

Let’s say that a few days ago, you modified one of the dovecot configuration files, but you forgot which one. You can easily filter all files under the /etc/dovecot/conf.d directory that ends with .conf and has been modified in the last five days:

find /etc/dovecot/conf.d -name "*.conf" -mtime 5

Here is another example of filtering files based on the modification date using the -daystart option. The command below will list all files in the /home directory that were modified 30 or more days ago:

find /home -mtime +30 -daystart

Find Files by Permissions

The -perm option allows you to search for files based on the file permissions.

For example, to find all files with permissions of exactly 775 inside the /var/www/html directory, you would use:

find /var/www/html -perm 644

You can prefix the numeric mode with minus – or slash /.

When slash / is used as the prefix, then at least one category (user, group, or others) must have at least the respective bits set for a file to match.

Consider the following example command:

find . -perm /444

The above command will match all the files with read permissions set for either user, group, or others.

If minus - is used as the prefix, then for the file to match, at least the specified bits must be set. The following command will search for files that have read and write permission for the owner and group and are readable by other users:

find . -perm -664

Find Files by Owner

To find files owned by a particular user or group, use the -user and -group options.

For example, to search for all files and directories owned by the user liviu-test, you would run:

find / -user liviu-test

Here is a real-world example. Let’s say you want to find all files owned by the user www-data and change the ownership of the matched files from www-data to nginx:

find / -user www-data -type f  -exec chown nginx {} \;

Find and Delete Files

To delete all matching files, append the -delete option to the end of the match expression.

Ensure you are using this option only when you are confident that the result matches the files you want to delete. It is always a good idea to print the matched files before using the -delete option.

For example, to delete all files ending with .temp from the /var/log/, you would use:

find /var/log/ -name `*.temp` -delete

Use the -delete option with extreme caution. The find command is evaluated as an expression and if you add the -delete option first, the command will delete everything below the starting points you specified.

When it comes to directories, find can delete only empty directories, same as rmdir .

Conclusion

We have shown you how to use the find command with various options and criteria.