Basic usage of find command in Linux
Common file search commands in Linux: locate, find, ag.
Introduction
In Linux, the find command is used to search for files and directories in a specified directory hierarchy. It is a powerful tool that can locate files based on various criteria such as name, size, type, and modification time.
locate
Simple to use, searches based on database, not real-time. Usage:
locate FILENAME
Manually update database (may take some time):
updatedb
find
Real-time, precise, powerful. Usage:
find PATH SEARCH_STANDARD SEARCH_ACTION
(1) PATH: “.” or “./” both represent current directory
(2) SEARCH_STANDARD:
-name 'FILENAME' Exact filename match (supports wildcard * ? [])
-iname 'FILENAME' Fuzzy filename match (case-insensitive)
-regex PATTERN Regular expression match
-user USERNAME Search based on owner
-group GROUP Search based on group
-uid UID
-gid GID
-nouser Files without owners
-type Search based on file type
-type f File
-type d Directory
-type c Character device
-type b Block device
-type l Link
-type p Pipe
-type s Socket
-size Search based on file size
-size 10k
-size 25M
-size 3G
-size +10k Files larger than 10k
-size -5M Files smaller than 5M
Combination options:
-a AND
-o OR
-not NOT
Search based on time:
-mtime modified time (default unit: days)
-ctime change time
-atime access time
-ctime +5 Changed over 5 days ago
-access -3 Accessed within the last 3 days
-mmin (default unit: minutes)
-cmin
-amin
Search based on permissions:
-perm 755 Exact permission
-perm /644 Any of the three digits match
-perm -700 Includes 600/500/.../000
Example 1: Find all regular files without owners in /tmp
find /tmp -nouser -a -type d
Example 2: Find files in /etc that are neither regular files nor directories
find /etc -not \( -type d -o -type f \)
(3) SEARCH_ACTION:
-print Default action
-ls List
-ok COMMAND \; Requires confirmation to execute COMMAND
-exec COMMAND \; Executes COMMAND without confirmation
Example 3: Find all files in current directory with permission 600 and display their sizes ({} represents found files, \; represents end)
find . -perm 600 -exec du {} \;
Example 4: Find all files in current directory with permission 400 and add “.new” to their filenames
find ./ -perm 400 -exec mv {} {}.new \;
Conclusion
The find command is a powerful tool for searching for files and directories in Linux. With its advanced search criteria and ability to execute commands on each file found, it can be an invaluable tool for managing large file systems.
