Useful Find command examples in UNIX

Find command is one of the most useful commands in UNIX, as there are many options out there to accomplish various search tasks.

• Find files which have been modified for more than or less than a certain time
We can use 'find * -mtime n' to search files under current directory based on modification time. The numeric argument n can be specified as +n, meaning greater than n days; -n, meaning less than n days; or n, meaning exactly n days. For example,
to find files which were last modified for more than 30 days ago

find . -mtime +30

to find files which were last modified for less than 15 days ago

find . -mtime -15

to find files which were last modified for exactly 10 days ago

find . -mtime 10

There are other options like

-mmin n, which refers to file's data was last modified n minutes ago
-amin n, which refers to file's data was last accessed n minutes ago
-atime n, which refers to file's data was last accessed n days ago
-type f, which searches for regular file
-type d, which searches for directory,
-exec command, which executes command by passing in the find results,
-perm /mode, which searches files with given permission 

• Remove files which are older than n days
Since we understand how to search for files which were last modified for more than n days, we can then use the rm command to remove them

find /some-dir/* -mtimes +30 -type f -exec rm {} \;

'-exec' is used to pass in commands like 'rm'; '{}' is replaced by the file name that 'find' returns; and the '-exec' command has to end with '\;'.
Another way will be

find /some-dir/* -mtimes +30 -type f -print0 | xargs -0 rm

where 'xargs' reads 'find' results and execute 'rm' on each of the 'find' results
• Find files which contain particular strings
Below is an example to search all txt files starting from current directory for string "some-string"

find . -name "*.txt" -print | xargs grep "some-string"