15条 linux Find 命令实际使用方法

This article is written by SathiyaMoorthy

作者： SathiyaMoorthy
 
Apart from the basic operation of looking for files under a directory structure, you can also perform several practical operations using find command that will make your command line journey easy.

Find命令除了在目录结构中查找文件之外，还可以用来做一些其他比较有实际意义的操作。
 
In this article, let us review 15 practical examples of Linux find command that will be very useful to both newbies and experts.

本文中的15条tips，对老鸟和菜鸟都会很有帮助

First, create the following sample empty files under your home directory to try some of the find command examples mentioned below.

首先在你的HOME目录下建立一些空的文件，并尝试下面的一些命令。

# vim create_sample_files.sh //使用vi创建文件，并输入下面的内容
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 //添加可运行属性

# ./create_sample_files.sh //运行脚本

# ls -R //查看执行的结果
.:
backup MybashProgram.sh MyCProgram.c
create_sample_files.sh mycprogram.c Program.c

./backup:
MybashProgram.sh mycprogram.c MyCProgram.c Program.c

1. Find Files Using Name 根据文件名查找

This is a basic usage of the find command. This example finds all files with name — MyCProgram.c in the current directory and all it’s sub-directories.

这个是Find命令最基本的操作，下面的例子是在当前目录和它所有子目录中查找MyCProgramm.c

# find -name "MyCProgram.c"
./backup/MyCProgram.c
./MyCProgram.c

2. Find Files Using Name and Ignoring Case 在1的基础上忽略文件名的大小写

This is a basic usage of the find command. This example finds all files with name — MyCProgram.c (ignoring the case) in the current directory and all it’s sub-directories.

这也是Find命令的基本操作之一.下面的例子是在当前目录及所有子目录中查找MyCProgram.c(忽略大小写)

# find -iname "MyCProgram.c"
./mycprogram.c
./backup/mycprogram.c
./backup/MyCProgram.c
./MyCProgram.c

3. Limit Search To Specific Directory Level Using mindepth and maxdepth

     查找指定目录并且设置查找的目录深度

Find the passwd file under all sub-directories starting from root directory.

下面的例子是在根目录及所有子目录中查找passwd文件

# find / -name passwd
./usr/share/doc/nss_ldap-253/pam.d/passwd
./usr/bin/passwd
./etc/pam.d/passwd
./etc/passwd

Find the passwd file under root and one level down. (i.e root — level 1, and one sub-directory — level 2)

查找根目录和根目录的和只展开一级的子目录中查找

# find -maxdepth 2 -name passwd
./etc/passwd

Find the passwd file under root and two levels down. (i.e root — level 1, and two sub-directories — level 2 and 3 )

在根目录和根目录下展开两级查找passwd文件

# find / -maxdepth 3 -name passwd
./usr/bin/passwd
./etc/pam.d/passwd
./etc/passwd

Find the password file between sub-directory level 2 and 4.

在根目录的第二级和第四级之间查找

# find -mindepth 3 -maxdepth 5 -name passwd
./usr/bin/passwd
./etc/pam.d/passwd

4. Executing Commands on the Files Found by the Find Command.

     查找到文件后，执行其他的命令

In the example below, the find command calculates the md5sum of all the files with the name MyCProgram.c (ignoring case). {} is replaced by the current file name.

下面的例子展示了在查找到文件后，计算文件的MD5值

# find -iname "MyCProgram.c" -exec md5sum {} /;
d41d8cd98f00b204e9800998ecf8427e ./mycprogram.c
d41d8cd98f00b204e9800998ecf8427e ./backup/mycprogram.c
d41d8cd98f00b204e9800998ecf8427e ./backup/MyCProgram.c
d41d8cd98f00b204e9800998ecf8427e ./MyCProgram.c

5. Inverting the match. 查找不匹配的文件

Shows the files or directories whose name are not MyCProgram.c .Since the maxdepth is 1, this will look only under current directory.

查找文件名不是MyCProgramm.c的文件，注意由于maxdepth是1,将只在当前目录中查找。

# find -maxdepth 1 -not -iname "MyCProgram.c"
.
./MybashProgram.sh
./create_sample_files.sh
./backup
./Program.c

6. Finding Files by its inode Number. 根据inode number查找

Every file has an unique inode number, using that we can identify that file. Create two files with similar name. i.e one file with a space at the end.

某些时候，有些文件的文件名非常相似，肉眼比较难以分辨，这时候可以根据他们唯一的inode number进行查找

# touch "test-file-name" # touch "test-file-name " //这个文件名最后有一个空格
[Note: There is a space at the end]

# ls -1 test*
test-file-name
test-file-name

From the ls output, you cannot identify which file has the space at the end. Using option -i, you can view the inode number of the file, which will be different for these two files.

使用ls命令查看的时候，我们不能分辨这两个文件，使用ls命令的选项-i则可以查看他们的inode number

# ls -i1 test*
16187429 test-file-name
16187430 test-file-name

You can specify inode number on a find command as shown below. In this example, find command renames a file using the inode number.

在使用find命令的时候可以指定inode number

# find -inum 16187430 -exec mv {} new-test-file-name /;

# ls -i1 *test*
16187430 new-test-file-name
16187429 test-file-name

You can use this technique when you want to do some operation with the files which are named poorly as shown in the example below. For example, the file with name — file?.txt has a special character in it. If you try to execute “rm file?.txt”, all the following three files will get removed. So, follow the steps below to delete only the “file?.txt” file.

这个技巧还可以适用于当文件名中存在特殊字符的情况

# ls
file1.txt file2.txt file?.txt

Find the inode numbers of each file.

# ls -i1
804178 file1.txt
804179 file2.txt
804180 file?.txt

Use the inode number to remove the file that had special character in it as shown below.

使用inodenumber删除包含特殊字符的文件

# find -inum 804180 -exec rm {} /; # ls
file1.txt file2.txt
[Note: The file with name "file?.txt" is now removed]

7. Find file based on the File-Permissions

根据文件的权限查找

Following operations are possible.

可以进行以下的这几种操作

• Find files that match exact permission
• Check whether the given permission matches, irrespective of other permission bits
• Search by giving octal / symbolic representation

For this example, let us assume that the directory contains the following files. Please note that the file-permissions on these files are different.

# ls -l
total 0
-rwxrwxrwx 1 root root 0 2009-02-19 20:31 all_for_all
-rw-r--r-- 1 root root 0 2009-02-19 20:30 everybody_read
---------- 1 root root 0 2009-02-19 20:31 no_for_all
-rw------- 1 root root 0 2009-02-19 20:29 ordinary_file
-rw-r----- 1 root root 0 2009-02-19 20:27 others_can_also_read
----r----- 1 root root 0 2009-02-19 20:27 others_can_only_read

Find files which has read permission to group. Use the following command to find all files that are readable by the world in your home directory, irrespective of other permissions for that file.

# find . -perm -g=r -type f -exec ls -l {} /;
-rw-r--r-- 1 root root 0 2009-02-19 20:30 ./everybody_read
-rwxrwxrwx 1 root root 0 2009-02-19 20:31 ./all_for_all
----r----- 1 root root 0 2009-02-19 20:27 ./others_can_only_read
-rw-r----- 1 root root 0 2009-02-19 20:27 ./others_can_also_read

Find files which has read permission only to group.

# find . -perm g=r -type f -exec ls -l {} /;
----r----- 1 root root 0 2009-02-19 20:27 ./others_can_only_read

Find files which has read permission only to group [ search by octal ]

# find . -perm 040 -type f -exec ls -l {} /;
----r----- 1 root root 0 2009-02-19 20:27 ./others_can_only_read

8. Find all empty files (zero byte file) in your home directory and it’s subdirectory

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

# find ~ -empty

List all the empty files only in your home directory.

# find . -maxdepth 1 -empty

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

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

9. Finding the Top 5 Big Files

The following command will display the top 5 largest file in the current directory and it’s subdirectory. This may take a while to execute depending on the total number of files the command has to process.

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

10. Finding the Top 5 Small Files

Technique is same as finding the bigger files, but the only difference the sort is ascending order.

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

In the above command, most probably you will get to see only the ZERO byte files ( empty files ). So, you can use the following command to list the smaller files other than the ZERO byte files.

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

11. Find Files Based on file-type using option -type

Find only the socket files.

# find . -type s

Find all directories

# find . -type d

Find only the normal files

# find . -type f

Find all the hidden files

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

Find all the hidden directories

# find -type d -name ".*"

12. Find files by comparing with the modification time of other file.

Show files which are modified after the specified file. The following find command displays all the files that are created/modified after ordinary_file.

# ls -lrt
total 0
-rw-r----- 1 root root 0 2009-02-19 20:27 others_can_also_read
----r----- 1 root root 0 2009-02-19 20:27 others_can_only_read
-rw------- 1 root root 0 2009-02-19 20:29 ordinary_file
-rw-r--r-- 1 root root 0 2009-02-19 20:30 everybody_read
-rwxrwxrwx 1 root root 0 2009-02-19 20:31 all_for_all
---------- 1 root root 0 2009-02-19 20:31 no_for_all

# find -newer ordinary_file
.
./everybody_read
./all_for_all
./no_for_all

13. Find Files by Size

Using the -size option you can find files by size.

Find files bigger than the given size

# find ~ -size +100M

Find files smaller than the given size

# find ~ -size -100M

Find files that matches the exact given size

# find ~ -size 100M

Note: – means less than the give size, + means more than the given size, and no symbol means exact given size.

14. Create Alias for Frequent Find Operations

If you find some thing as pretty useful, then you can make it as an alias. And execute it whenever you want.

Remove the files named a.out frequently.

# alias rmao="find . -iname a.out -exec rm {} /;"
# rmao

Remove the core files generated by c program.

# alias rmc="find . -iname core -exec rm {} /;"
# rmc

 

15. Remove big archive files using find command

The following command removes *.zip files that are over 100M.

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

Remove all *.tar file that are over 100M using the alias rm100m (Remove 100M). Use the similar concepts and create alias like rm1g, rm2g, rm5g to remove file size greater than 1G, 2G and 5G respectively.

# 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

This article was written by SathiyaMoorthy, author of numbertotext Vim plugin, which will replace the numbers with the equivalent text inside Vim. The Geek Stuff welcomes your tips and guest articles.

How do you use find command? What is your favorite find command example? Please leave a comment and let us know. Also, if you would like to know how to use find command under a specific scenario, please let us know your questions in the comments section.