JIYIK CN >

In addition to the basic operation of finding files under the directory structure, we can also use findthe command to perform some practical operations, which will make our command line journey easy.

In this article, let us review 15 findpractical examples of Linux commands that are useful for newbies and experts alike.

First, create the following sample empty file in your home directory so that you can easily try out some of findthe command examples mentioned below.

$ vim create_sample_files.sh
touch MybashProgram.sh
touch mycprogram.c
touch MyCProgram.c
touch Program.c

mkdir backup
cd backup

touch MybashProgram.sh
touch mycprogram.c
touch MyCProgram.c
touch Program.c

$ chmod +x create_sample_files.sh

$ ./create_sample_files.sh

Check the running results as follows

1. Find a file using its name

This is the basic usage of the command. This example finds all files with the name MyCProgram.cfind in the current directory and all its subdirectories .

$ find -name "MyCProgram.c"

2. Find files using name and ignore case

This is the basic usage of the command. This example finds all files with the name MyCProgram.cfind (ignoring case) in the current directory and all its subdirectories .

$ find -iname "MyCProgram.c"

3. Use mindepth and maxdepth to limit the search to a specific directory level

Find the passwd file in all subdirectories starting from the root directory .

$ find / -name passwd

Find the passwd file in the root directory and go down one level. (i.e. root directory - 1 level, one subdirectory - 2 levels)

$ find / -maxdepth 2 -name passwd

Find the passwd files in both levels of root . (i.e. root — level 1, and two subdirectories — levels 2 and 3)

$ find / -maxdepth 3 -name passwd

Locate the passwd file between subdirectory levels 2 and 4 .

$ find / -mindepth 3 -maxdepth 5 -name passwd

4. Execute commands on files found by Find command

In the following example, findthe command evaluates all files with the name MyCProgram.cmd5sum (ignoring case). {}Replace with the current file name.

$ find -iname "MyCProgram.c" -exec md5sum {} \;

5. Reverse the search results

Displays files or directories whose names are not MyCProgram.c . Since maxdepth is 1, only the current directory is searched.

$ find -maxdepth 1 -not -iname "MyCProgram.c"

6. Find the file by inode Number.

Each file has a unique inode number using which we can identify the file. Create two files with similar names. i.e. one file has a space at the end.

$ touch "test-file-name"

$ touch "test-file-name " # 注意这后面的空格
[Note: There is a space at the end]

$ ls -1 test*

The results of viewing the file are as follows

From the ls output, we cannot tell which file has the trailing space. Using the -l option -iwe can see inodethe numbers of the files, which will be different for the two files.

$ ls -i1 test*

We can findspecify the inode number on the command as shown below. In this example, the command renames the file findusing the inode number.

$ find -inum 37945133 -exec mv {} new-test-file-name \;

$ ls -i1 *test*

We can use this when we want to do something with a poorly named file, as shown in the following example. For example, file?.txta file named - contains a special character. If we try to execute rm file?.txt, all three of the following files will be deleted. So, follow these steps to delete only the " file?.txt " file.

$ ls
file1.txt  file2.txt  file?.txt

Find the inode number of each file.

$ ls -i1

Delete the files having special characters in them using inode number as shown below.

$ find -inum 37945122 -exec rm {} \;

7. Find files based on file permissions

The following operations can be performed.

• Find files matching exact permissions
• Checks whether the given permission matches, regardless of other permission bits.
• Search by giving octal/symbolic representation

For this example, let's assume that the directory contains the following files. Note that the file permissions for these files are different.

$ ls -l

Find (x)files that have execute permission for the group. Use the following command to find all files in our home directory that are executable, regardless of the other permissions of the file.

$ find . -perm -g=x -type f -exec ls -l {} \;

Find files that have read permissions only for the group.

$ find . -perm g=r -type f -exec ls -l {} \;

Find files with read permissions only for group [search by octal]

$ find . -perm 040 -type f -exec ls -l {} \;

8. Find all empty files (zero-byte files) in your home directory and its subdirectories

Most of the files output by the following command will be lock files and placeholders created by other applications.

$ find ~ -empty

Just list all the empty files in our home directory.

$ find . -maxdepth 1 -empty

List only non-hidden, empty files in the current directory.

$ find . -maxdepth 1 -empty -not -name ".*"

9. Find the top 5 largest files

The following command will display the top 5 largest files in the current directory and its subdirectories. This may take a while to execute, depending on the total number of files the command must process.

$ find . -type f -exec ls -s {} \; | sort -n -r | head -5

10. Find the top 5 small files

The method is the same as for finding larger files, but the only difference in sorting is ascending.

$ find . -type f -exec ls -s {} \; | sort -n  | head -5

In the above command, it is likely that we will see only zero-byte files (empty files). So, we can use the following command to list the smaller files except the zero-byte files.

$ find . -not -empty -type f -exec ls -s {} \; | sort -n  | head -5

11. Use option -type to find files based on file type

Only socket files are found.

$ find . -type s

Search all directories

$ find . -type d

Search only regular files

$ find . -type f

Find all hidden files

$ find . -type f -name ".*"

Find all hidden directories

$ find -type d -name ".*"

12. Find files by comparing modification time of other files

Displays files modified after the specified file. The following findcommand displays all the files created/modified after test-file-name .

$ find -newer test-file-name

13. Find files by size

Using the -size option, we can search for files by size.

Find files larger than a given size

$ find ~ -size +100M

Find files smaller than a given size

$ find ~ -size -100M

Find files that exactly match a given size

$ find ~ -size 100M

注意: - means less than the given size, + means greater than the given size, and unsigned means the exact given size.

14. Create aliases for frequent lookup operations

If you find some lookup operation is very useful, you can set it as an alias and execute it at any time.

Frequently delete files named a.out .

$ alias rmao="find . -iname a.out -exec rm {} \;"
$ rmao

Delete the core files generated by the c program.

$ alias rmc="find . -iname core -exec rm {} \;"
$ rmc

15. Use find command to delete large archive files

The following command deletes files larger than 100M *.zip.

$ find / -type f -name *.zip -size +100M -exec rm -i {} \;"

Use an alias rm100mto delete all files larger than 100M *.tar(delete100M). Use a similar concept and create aliases like rm1g, to delete files larger than 1G , 2G , and 5Grm2g respectively .rm5g

$ alias rm100m="find / -type f -name *.tar -size +100M -exec rm -i {} \;"
$ alias rm1g="find / -type f -name *.tar -size +1G -exec rm -i {} \;"
$ alias rm2g="find / -type f -name *.tar -size +2G -exec rm -i {} \;"
$ alias rm5g="find / -type f -name *.tar -size +5G -exec rm -i {} \;"

$ rm100m
$ rm1g
$ rm2g
$ rm5g