Find, Locate, and Grep

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FIND

Find is a linux search tool that can be used to find a variety of files based on the given criteria.

find [options] {search location} {search criteria} [actions]

OPTION	Function
-type	Specify the file type for the search. Either f or d.
-name	Specify file/directory name to search for
-perm	Specify file permissions to search for.
-size	Find files based on file size.
-user & -group	Find files based on ownership properties.
-mmin -00	Find files that have been updated within a specified number of minutes.
ACTION	FUNCTION
-print	Print the specific path of files found.
-exec	Execute a command on the files found.
-delete	Delete the files found.
-fprint	Store the findings in a target file.

Basic find

find / -type f -name hello.txt

wildcards

find / -name "*.txt"

Discard errors (ie permission denied)

find / -name "*.txt" 2>/dev/null

 Find files with specific permissions

Find files with read,write, and execute permissions

find / -perm +rwx

Find files by size

Find files that are greater than 2MB:

find / -size +2M

Find files that are less than 2MB:

find / -size -2M

Find files that are exactly 2MB:

find / -size 2M

Find files by owner/group

Find files based on group

find / -group groupname

Find files based on owner

find / -user username

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LOCATE

Locate is similar to find in its functionality, but it operates quite differently. Locate performs quick searches using its own mlocate database - a database of files that are stored on a server. The database needs to be regularly updated in order for the locate command to work accurately.

Update mlocate DB

updatedb

Locate file based on name

locate [options] test.txt

Option	Function
-r	Search file names using regex
-c	Count the number of matching entries found
-e	Return only files that exist at the time of the search
-i	Ignore casing
--n [number of entries]	Retirn the first few matches up to the specified number.

Additional configuration for locate command

The mlocate database used by the locate command is stored at;
/var/lib/mlocate/mlocate.db

The configuration for this database is stored at;
/etc/updatedb.conf

Within this config file, you can add exclusions for directories to be skipped within the mlocate DB, this is done using the below syntax;
PRUNEPATH = "/path/to/exclude"

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GREP

Option	Function
-i	Case insensitive
-v	Exclude string
'string|string'	OR Statement - used to search for multiple strings.
-r	Recursive
-A & -B	After & Before - used to specify a number of lines either before or after a specified string is found.
-E	Extended Regular Expression.

Extended regular expression

Regular expression is essentially the methodology that we can use to manipulate grep to find advanced string patterns.

Special characters

When trying to grep for special characters, you need to make sure to 'escape' those characters, this is done by proceeding special characters with a \:

grep -E year\'s

Beginning and end of line

line begins with

The below example would show any lines beginning with the character '1'

grep -E "^1" filename

line ends with

The below example would show any lines ending with the character '1'

grep -e "1$" filename

Ranges

grep interprets ranges that are defined through square brackets []. 

line begins with 1 and is followed by numbers in the 0-2 range:

grep -E "^1[0-2]" filename

We can also search for ranges of letters

The below command would search for the letter b, proceeded by any letter in the specified range, followed by the letter g:

grep -E "b[aeiou]g" filename

We can also search a range of letters like this:

grep -E "b[a-z]g" filename

You can also combine ranges

grep -E "b[a-z,A-Z]g" filename

Wildcards

There are a number of wildcard options available to use in egrep.

. - any single character

grep -e "c.t" filename

• Matches: "cat", "cot", "cut", etc.
• Does not match: "ct", "caat"

* - matches zero or more occurrences of the preceding character

grep -e "g*d" filename

• Matches: "gd", "god", "good", "goood"
• Does not match: "go", "goooo", "gdo", "goddy"

.* - match zero or more of any character

grep -e "a.*b" filename

• Matches: "ab", "acb", "axyzb", "a123b"
• Does not match: "a b", "ab ", "acbd", "a"

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