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.

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Basic find

find targetdirectory -name stringtofind

find / -name hello.txt

wildcards

find / -name "*.txt"

Discard errors (ie permission denied)

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

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 Find files with specific permissions

Find files with read,write, and execute permissions

find / -perm +rwx

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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

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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, however,but thereit areoperates somequite importantdifferently. distinctions:

• Locate keepsperforms it'squick searches using its own mlocate database - a database of files that are stored on a system
server.
• LocateThe isdatabase less disk IO intensive since it doesn't haveneeds to scanbe regularly updated in order for the whole hard drive for files, instead it references it's own database.
• Locate isn't installed by default on most systems, the package name is mlocate. Once installed, you'll need to run the updatedlocate command to updatework locate'saccurately.
  database

  Update -mlocate thisDB

  should really be updated every time you use the command

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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

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-i - case insensitive

As with all of Linux, grep is case sensitive. The -i flag can be passed to ignore case type.

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-v -exclude string

The -v flag is used to exclude a string from an output.

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| - or statement

The below will search for string1 or string2 within a file, if both are found then both will be outputted.

grep 'string1|string2' filename

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-r - search files recursively 

grep -r hello /

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-A & -B (before and after)

Sometimes you might want to search for a string, and see the lines before/after that string.

The below will show the 2 lines following the string

grep -A2 string filename

The below will show the 2 lines before the string

grep -B2 string filename

You can also combine these to see the lines before and after

grep -A2 -B2 string filename

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-E or egrep - extended regular expression

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

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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

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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

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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

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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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