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.txtwildcards
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 +2MFind files that are less than 2MB:
find / -size -2MFind files that are exactly 2MB:
find / -size 2M------------------------------------------------------------------------------------------------------------------------------------------------
Find files by owner/group
Find files based on group
find / -group groupnameFind files based on owner
find / -user username====================================================================================
LOCATE
Locate is similar to find in its functionality, however, there are some important distinctions:
- Locate keeps it's own database of files on a system
- Locate is less disk IO intensive since it doesn't have to scan 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 updated command to update locate's database - this should really be updated every time you use the command
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Locate file based on name
locate test.txt====================================================================================
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------------------------------------------------------------------------------------------------------------------------------------------------
-r - search files recursively
grep -r hello /------------------------------------------------------------------------------------------------------------------------------------------------
-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 filenameThe below will show the 2 lines before the string
grep -B2 string filenameYou can also combine these to see the lines before and after
grep -A2 -B2 string filename====================================================================================
-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------------------------------------------------------------------------------------------------------------------------------------------------
Beginning and end of line
line begins with
The below example would show any lines beginning with the character '1'
grep -E "^1" filenameline 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]" filenameWe 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" filenameWe can also search a range of letters like this:
grep -E "b[a-z]g" filenameYou 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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