grep and find are such powerful commands to find resources quickly. The syntax is convenient and you can combine options at will to filter results.

grep

GREP stands for "global regular expression print" and is helpful to search chars and patterns, and filter information in big chunks of data.

7 Basic commands

1. search term (case insensitive)

grep -i "mimiKAtZ" security.log

2. display line numbers

grep -n "mimikatz" security.log

3. search in dir

grep -r "mimikatz" ./

4. exact matches

grep -w "h4ck3r" security.log

5. count results

grep -c "h4ck3r" security.log

6. get filenames only

grep -l "h4ck3r" ./mydir

7. reverse the pattern

grep -v "RTFM" README.md

Common Options

Be aware it's not an exhaustive list:

7 Advanced usages

1. grep in multiple files

grep "h4ck3r" 1.log 2.log 3.log .4log

2. exclude file extensions

grep -rl --exclude=*.{sh,txt} ./

3. exclude dirs

grep -r --exclude-dir={root,log,proc,sys} "test" ./

4. include specific file extension

grep -nr "eth0" --include="*.conf" /etc/

5. only target lines that start with alphanumeric chars

grep "^[[:alnum:]]" README.md

6. another way for exact matches (-w)

grep "\bsudo\b" /etc/

7. quickly list php files (common usage):

ls | grep ".php"

7 Nice tricks

1. multiple searches at the same time

grep -E "^(sudo|root|system)" /etc/

2. grep is taking too long? time it!

time grep "e" ./

3. pipe grep to narrow searches

grep "[nN]urse" romeo-and-juliet.txt | grep -v "\[_.*Nurse.*_]"

Source: https://www.shell-tips.com/linux/grep/#how-to-grep

4. search in all derivatives of an expression (lov)

grep -i "\blov.\+\b" romeo-and-juliet.txt

Source: https://www.shell-tips.com/linux/grep/#how-to-grep

5. pipe grep output to another program

grep -rA 2 "bin/.*sh" ~/scripts | less

Source: https://www.shell-tips.com/linux/grep/#how-to-grep

6. grep in big .gz files without opening them

zgrep -ic "h4ck3r" logs.gz

7. shorten ranges in grep searches

grep {1..7} error.log

Simple or double quotes for search terms?

It depends on what you want to achieve, but in case you need to use a shell variable, which is a pretty common usage, use double quotes.

How to highlight search terms with colors?

It's usually handled by the system itself, but if it's not the case, you can use the following alias in your .bashrc:

alias grep='grep --color=auto'

Commands for hackers

Go check hacktricks

find

find is a command-line utility you can use to search a list of files or directories and apply functions on them.

7 basic commands

1. find a file

find ./ myfile.json

2. find a file by its name

find ./mydir -name myfile

3. case insensitive search

find ./mydir -iname mYfILE

4. find directories within a dir

find ./mydir -type d

5. find in multiple dirs by filename

find ./mydir /mydir2/subdir -type f -name myfile

6. exclude name "README"

find ./mydir -not README

7. find and delete JSON files

find ./mydir –name "*.json" –delete

Common Types

Size units

7 advanced usages

N.B.: When I write -/+, it means either - for smaller or + for bigger than. Don't use the /

1. find by size

find ./mydir -size 1M

2. find by size smaller/bigger than

find ./mydir -size -/+1M

3. find by permission

find ./mydir -perm 777

4. find by X last modified days

find ./mydir -mtime X

X is an integer.

5. find stuff of user X

find ./mydir -user ulysse31

6. find empty folders

find ./mydir -type d -empty

7. limit depth to 2 levels

find -maxdepth 2 ./mydir -type f -name lola

7 nice tricks

1. quickly search in current user homedir

find ~ -type f -name "todo"

2. find files accessed in the last 3 hours

find ./mydir -amin -180

3. find all files matching pattern "[0-9]"

find ./mydir -type f -name "*[0-9]"

4. find read-only files

find ./dir -perm /u=r

5. apply ls -lah on each search result

find ./mydir -type f -name "*.json" -exec ls -lah {} \;

or

find . -type f -name *.json" | xargs ls -lah

6. set permissions for all dirs

find ./mydir -type d -exec chmod 0755 {} \;

or

find ./mydir -type d -print0 | xargs -0 chmod 0755

7. set permissions for all files

find ./mydir -type d -exec chmod 0644 {} \;` or `find ./mydir -type f -print0 | xargs -0 chmod 0644

About find, grep, and more complex commands

There are dozens of combos you might want to try, for example, applying grep on each result of the find command. While it's totally possible, I like to keep it simple, as, most of the time, I only need speed.

If you need more complexity, you can try combos with | (pipe) or use the -exec option:

find . -type f -iname "*.json" -exec grep -L "Wanna be startin' somethin'" {} \;

Remove the annoying "permission denied"

In this cheat sheet, I often use ./mydir as haystack, but if you need more global search, you will probably get messages like "permission denied," as there are system binaries and protected resources you're not supposed to read with your user account.

To remove useless lines, you can send the output to /dev/null at the end of the command line:

COMMAND 2> /dev/null

It's also possible to combine find and grep to achieve the same goal:

find / -type d -name secret 2>&1 | grep -v "Permission denied"

Wrap up

Use grep and find to save time and energy.

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