Useful Linux Commands
# add text to the start of a line
sed -i -e 's_.*_REPLACETHIS&_' <filename>
# Will remove the word Javascript from the file cewlfile
cat cewlfile | tr -d \[:CHAR:Javascript\]

RTFM

Useful tool help remind you of command syntax

git clone https://github.com/leostat/rtfm
cd rtfm
pip3 install terminaltables
./rtfm.py -e hydra #EXAMPLE
# 1. redo last command but as root
sudo !!
# 2. open an editor to run a command
ctrl+x+e
# 3. create a super fast ram disk
mkdir -p /mnt/ram
mount -t tmpfs tmpfs /mnt/ram -o size=8192M
# 4. don't add command to history (note the leading space)
ls -l
# 5. fix a really long command that you messed up
fc
# 6. tunnel with ssh (local port 3337 -> remote host's 127.0.0.1 on port 6379)
ssh -L 3337:127.0.0.1:6379 [email protected] -N
# 7. quickly create folders
mkdir -p folder/{sub1,sub2}/{sub1,sub2,sub3}
# 8. intercept stdout and log to file
cat file | tee -a log | cat > /dev/null
# bonus: exit terminal but leave all processes running
disown -a && exit

Commands Explained

https://explainshell.com/

Kill a process using a port

lsof -t -i:443
kill -9 $PID

Append to end of file

echo 'text here' >> filename

sed

FILE SPACING:
# remove white spacing from a file
sed "s/^[ \t]*//" -i $filename
# extract ports from nmap scan
sed 's/\/tcp.*//g' ports
# then use this command to pring out ports as comma seperated values
awk -vORS=, '{ print $1 }' ports | sed 's/,$/\n/'
# double space a file
sed G
# double space a file which already has blank lines in it. Output file
# should contain no more than one blank line between lines of text.
sed '/^$/d;G'
# triple space a file
sed 'G;G'
# undo double-spacing (assumes even-numbered lines are always blank)
sed 'n;d'
# insert a blank line above every line which matches "regex"
sed '/regex/{x;p;x;}'
# insert a blank line below every line which matches "regex"
sed '/regex/G'
# insert a blank line above and below every line which matches "regex"
sed '/regex/{x;p;x;G;}'
NUMBERING:
# number each line of a file (simple left alignment). Using a tab (see
# note on '\t' at end of file) instead of space will preserve margins.
sed = filename | sed 'N;s/\n/\t/'
# number each line of a file (number on left, right-aligned)
sed = filename | sed 'N; s/^/ /; s/ *\(.\{6,\}\)\n/\1 /'
# number each line of file, but only print numbers if line is not blank
sed '/./=' filename | sed '/./N; s/\n/ /'
# count lines (emulates "wc -l")
sed -n '$='
TEXT CONVERSION AND SUBSTITUTION:
# IN UNIX ENVIRONMENT: convert DOS newlines (CR/LF) to Unix format.
sed 's/.$//' # assumes that all lines end with CR/LF
sed 's/^M$//' # in bash/tcsh, press Ctrl-V then Ctrl-M
sed 's/\x0D$//' # works on ssed, gsed 3.02.80 or higher
# IN UNIX ENVIRONMENT: convert Unix newlines (LF) to DOS format.
sed "s/$/`echo -e \\\r`/" # command line under ksh
sed 's/#x27;"/`echo \\\r`/" # command line under bash
sed "s/$/`echo \\\r`/" # command line under zsh
sed 's/$/\r/' # gsed 3.02.80 or higher
# IN DOS ENVIRONMENT: convert Unix newlines (LF) to DOS format.
sed "s/$//" # method 1
sed -n p # method 2
# IN DOS ENVIRONMENT: convert DOS newlines (CR/LF) to Unix format.
# Can only be done with UnxUtils sed, version 4.0.7 or higher. The
# UnxUtils version can be identified by the custom "--text" switch
# which appears when you use the "--help" switch. Otherwise, changing
# DOS newlines to Unix newlines cannot be done with sed in a DOS
# environment. Use "tr" instead.
sed "s/\r//" infile >outfile # UnxUtils sed v4.0.7 or higher
tr -d \r <infile >outfile # GNU tr version 1.22 or higher
# delete leading whitespace (spaces, tabs) from front of each line
# aligns all text flush left
sed 's/^[ \t]*//' # see note on '\t' at end of file
# delete trailing whitespace (spaces, tabs) from end of each line
sed 's/[ \t]*$//' # see note on '\t' at end of file
# delete BOTH leading and trailing whitespace from each line
sed 's/^[ \t]*//;s/[ \t]*$//'
# insert 5 blank spaces at beginning of each line (make page offset)
sed 's/^/ /'
# align all text flush right on a 79-column width
sed -e :a -e 's/^.\{1,78\}$/ &/;ta' # set at 78 plus 1 space
# center all text in the middle of 79-column width. In method 1,
# spaces at the beginning of the line are significant, and trailing
# spaces are appended at the end of the line. In method 2, spaces at
# the beginning of the line are discarded in centering the line, and
# no trailing spaces appear at the end of lines.
sed -e :a -e 's/^.\{1,77\}$/ & /;ta' # method 1
sed -e :a -e 's/^.\{1,77\}$/ &/;ta' -e 's/\( *\)\1/\1/' # method 2
# substitute (find and replace) "foo" with "bar" on each line
sed 's/foo/bar/' # replaces only 1st instance in a line
sed 's/foo/bar/4' # replaces only 4th instance in a line
sed 's/foo/bar/g' # replaces ALL instances in a line
sed 's/\(.*\)foo\(.*foo\)/\1bar\2/' # replace the next-to-last case
sed 's/\(.*\)foo/\1bar/' # replace only the last case
# substitute "foo" with "bar" ONLY for lines which contain "baz"
sed '/baz/s/foo/bar/g'
# substitute "foo" with "bar" EXCEPT for lines which contain "baz"
sed '/baz/!s/foo/bar/g'
# change "scarlet" or "ruby" or "puce" to "red"
sed 's/scarlet/red/g;s/ruby/red/g;s/puce/red/g' # most seds
gsed 's/scarlet\|ruby\|puce/red/g' # GNU sed only
# reverse order of lines (emulates "tac")
# bug/feature in HHsed v1.5 causes blank lines to be deleted
sed '1!G;h;$!d' # method 1
sed -n '1!G;h;$p' # method 2
# reverse each character on the line (emulates "rev")
sed '/\n/!G;s/\(.\)\(.*\n\)/&\2\1/;//D;s/.//'
# join pairs of lines side-by-side (like "paste")
sed '$!N;s/\n/ /'
# if a line ends with a backslash, append the next line to it
sed -e :a -e '/\\$/N; s/\\\n//; ta'
# if a line begins with an equal sign, append it to the previous line
# and replace the "=" with a single space
sed -e :a -e '$!N;s/\n=/ /;ta' -e 'P;D'
# add commas to numeric strings, changing "1234567" to "1,234,567"
gsed ':a;s/\B[0-9]\{3\}\>/,&/;ta' # GNU sed
sed -e :a -e 's/\(.*[0-9]\)\([0-9]\{3\}\)/\1,\2/;ta' # other seds
# add commas to numbers with decimal points and minus signs (GNU sed)
gsed -r ':a;s/(^|[^0-9.])([0-9]+)([0-9]{3})/\1\2,\3/g;ta'
# add a blank line every 5 lines (after lines 5, 10, 15, 20, etc.)
gsed '0~5G' # GNU sed only
sed 'n;n;n;n;G;' # other seds
SELECTIVE PRINTING OF CERTAIN LINES:
# print first 10 lines of file (emulates behavior of "head")
sed 10q
# print first line of file (emulates "head -1")
sed q
# print the last 10 lines of a file (emulates "tail")
sed -e :a -e '$q;N;11,$D;ba'
# print the last 2 lines of a file (emulates "tail -2")
sed '$!N;$!D'
# print the last line of a file (emulates "tail -1")
sed '$!d' # method 1
sed -n '$p' # method 2
# print the next-to-the-last line of a file
sed -e '$!{h;d;}' -e x # for 1-line files, print blank line
sed -e '1{$q;}' -e '$!{h;d;}' -e x # for 1-line files, print the line
sed -e '1{$d;}' -e '$!{h;d;}' -e x # for 1-line files, print nothing
# print only lines which match regular expression (emulates "grep")
sed -n '/regexp/p' # method 1
sed '/regexp/!d' # method 2
# print only lines which do NOT match regexp (emulates "grep -v")
sed -n '/regexp/!p' # method 1, corresponds to above
sed '/regexp/d' # method 2, simpler syntax
# print the line immediately before a regexp, but not the line
# containing the regexp
sed -n '/regexp/{g;1!p;};h'
# print the line immediately after a regexp, but not the line
# containing the regexp
sed -n '/regexp/{n;p;}'
# print 1 line of context before and after regexp, with line number
# indicating where the regexp occurred (similar to "grep -A1 -B1")
sed -n -e '/regexp/{=;x;1!p;g;$!N;p;D;}' -e h
# grep for AAA and BBB and CCC (in any order)
sed '/AAA/!d; /BBB/!d; /CCC/!d'
# grep for AAA and BBB and CCC (in that order)
sed '/AAA.*BBB.*CCC/!d'
# grep for AAA or BBB or CCC (emulates "egrep")
sed -e '/AAA/b' -e '/BBB/b' -e '/CCC/b' -e d # most seds
gsed '/AAA\|BBB\|CCC/!d' # GNU sed only
# print paragraph if it contains AAA (blank lines separate paragraphs)
# HHsed v1.5 must insert a 'G;' after 'x;' in the next 3 scripts below
sed -e '/./{H;$!d;}' -e 'x;/AAA/!d;'
# print paragraph if it contains AAA and BBB and CCC (in any order)
sed -e '/./{H;$!d;}' -e 'x;/AAA/!d;/BBB/!d;/CCC/!d'
# print paragraph if it contains AAA or BBB or CCC
sed -e '/./{H;$!d;}' -e 'x;/AAA/b' -e '/BBB/b' -e '/CCC/b' -e d
gsed '/./{H;$!d;};x;/AAA\|BBB\|CCC/b;d' # GNU sed only
# print only lines of 65 characters or longer
sed -n '/^.\{65\}/p'
# print only lines of less than 65 characters
sed -n '/^.\{65\}/!p' # method 1, corresponds to above
sed '/^.\{65\}/d' # method 2, simpler syntax
# print section of file from regular expression to end of file
sed -n '/regexp/,$p'
# print section of file based on line numbers (lines 8-12, inclusive)
sed -n '8,12p' # method 1
sed '8,12!d' # method 2
# print line number 52
sed -n '52p' # method 1
sed '52!d' # method 2
sed '52q;d' # method 3, efficient on large files
# beginning at line 3, print every 7th line
gsed -n '3~7p' # GNU sed only
sed -n '3,${p;n;n;n;n;n;n;}' # other seds
# print section of file between two regular expressions (inclusive)
sed -n '/Iowa/,/Montana/p' # case sensitive
SELECTIVE DELETION OF CERTAIN LINES:
# print all of file EXCEPT section between 2 regular expressions
sed '/Iowa/,/Montana/d'
# delete duplicate, consecutive lines from a file (emulates "uniq").
# First line in a set of duplicate lines is kept, rest are deleted.
sed '$!N; /^\(.*\)\n\1$/!P; D'
# delete duplicate, nonconsecutive lines from a file. Beware not to
# overflow the buffer size of the hold space, or else use GNU sed.
sed -n 'G; s/\n/&&/; /^\([ -~]*\n\).*\n\1/d; s/\n//; h; P'
# delete all lines except duplicate lines (emulates "uniq -d").
sed '$!N; s/^\(.*\)\n\1$/\1/; t; D'
# delete the first 10 lines of a file
sed '1,10d'
# delete the last line of a file
sed '$d'
# delete the last 2 lines of a file
sed 'N;$!P;$!D;$d'
# delete the last 10 lines of a file
sed -e :a -e '$d;N;2,10ba' -e 'P;D' # method 1
sed -n -e :a -e '1,10!{P;N;D;};N;ba' # method 2
# delete every 8th line
gsed '0~8d' # GNU sed only
sed 'n;n;n;n;n;n;n;d;' # other seds
# delete lines matching pattern
sed '/pattern/d'
# delete ALL blank lines from a file (same as "grep '.' ")
sed '/^$/d' # method 1
sed '/./!d' # method 2
# delete all CONSECUTIVE blank lines from file except the first; also
# deletes all blank lines from top and end of file (emulates "cat -s")
sed '/./,/^$/!d' # method 1, allows 0 blanks at top, 1 at EOF
sed '/^$/N;/\n$/D' # method 2, allows 1 blank at top, 0 at EOF
# delete all CONSECUTIVE blank lines from file except the first 2:
sed '/^$/N;/\n$/N;//D'
# delete all leading blank lines at top of file
sed '/./,$!d'
# delete all trailing blank lines at end of file
sed -e :a -e '/^\n*$/{$d;N;ba' -e '}' # works on all seds
sed -e :a -e '/^\n*$/N;/\n$/ba' # ditto, except for gsed 3.02.*
# delete the last line of each paragraph
sed -n '/^$/{p;h;};/./{x;/./p;}'
SPECIAL APPLICATIONS:
# remove nroff overstrikes (char, backspace) from man pages. The 'echo'
# command may need an -e switch if you use Unix System V or bash shell.
sed "s/.`echo \\\b`//g" # double quotes required for Unix environment
sed 's/.^H//g' # in bash/tcsh, press Ctrl-V and then Ctrl-H
sed 's/.\x08//g' # hex expression for sed 1.5, GNU sed, ssed
# get Usenet/e-mail message header
sed '/^$/q' # deletes everything after first blank line
# get Usenet/e-mail message body
sed '1,/^$/d' # deletes everything up to first blank line
# get Subject header, but remove initial "Subject: " portion
sed '/^Subject: */!d; s///;q'
# get return address header
sed '/^Reply-To:/q; /^From:/h; /./d;g;q'
# parse out the address proper. Pulls out the e-mail address by itself
# from the 1-line return address header (see preceding script)
sed 's/ *(.*)//; s/>.*//; s/.*[:<] *//'
# add a leading angle bracket and space to each line (quote a message)
sed 's/^/> /'
# delete leading angle bracket & space from each line (unquote a message)
sed 's/^> //'
# remove most HTML tags (accommodates multiple-line tags)
sed -e :a -e 's/<[^>]*>//g;/</N;//ba'
# extract multi-part uuencoded binaries, removing extraneous header
# info, so that only the uuencoded portion remains. Files passed to
# sed must be passed in the proper order. Version 1 can be entered
# from the command line; version 2 can be made into an executable
# Unix shell script. (Modified from a script by Rahul Dhesi.)
sed '/^end/,/^begin/d' file1 file2 ... fileX | uudecode # vers. 1
sed '/^end/,/^begin/d' "[email protected]" | uudecode # vers. 2
# sort paragraphs of file alphabetically. Paragraphs are separated by blank
# lines. GNU sed uses \v for vertical tab, or any unique char will do.
sed '/./{H;d;};x;s/\n/={NL}=/g' file | sort | sed '1s/={NL}=//;s/={NL}=/\n/g'
gsed '/./{H;d};x;y/\n/\v/' file | sort | sed '1s/\v//;y/\v/\n/'
# zip up each .TXT file individually, deleting the source file and
# setting the name of each .ZIP file to the basename of the .TXT file
# (under DOS: the "dir /b" switch returns bare filenames in all caps).
echo @echo off >zipup.bat
dir /b *.txt | sed "s/^\(.*\)\.TXT/pkzip -mo \1 \1.TXT/" >>zipup.bat

Copy output of command to clipboard

xclip -sel c < cat file.txt
Then Ctrl v to paste You may have to install xclip
apt-get install xclip

Crontab

  • Sytanx:
    minute hour day-month month day-week CMD
  • 1 * * * * $ cmd runs every minute

Extracting archives

  • tar xvfj test.tar.bz2
    tar zxvf test.tar.gz
    tar zxvf test.tar
    gzip -d test.gz
    unzip test.zip
    zcat rockyou.txt.gz > rockyou.txt

Compressing archives

  • tar -zcvf test.tar test
    gzip test
    zip -9 test.zip test
    zip -r test.zip test/

Copy files remotely

File Permissions

  • t rwx rwx rwx type / owner / group / world
  • Type is directory (d) or file (-).
  • read (r) 4
  • write (w) 2
  • execute (e) 1
  • chmod 755 test.sh Make a file executable
  • find . -name "*.php" -type f -exec chmod 755 {} \;

Finding Files

  • Update the database of file names on the system
    updatedb
  • Reads the database and shows the location of a file
    locate file
  • Show the path where the app is executed from
    which app
  • Show all the files that start with sbd
    find / -name sbd*
  • Show all world readable directories
    find / -perm -o+w -type d
  • Show all world executable directories
    find / -perm -o+e -type d

Searching within files

  • Search for the pattern xxx in a fil
    grep xxx file
  • Search recursively for a pattern in a director
    grep -r
  • Search for a pattern in a zip file
    zgrep

Locate, Which, Find

Locate

updatedb # builds local database of all files on system
$ locate nc.exe
/usr/share/windows-binaries/nc.exe

Which

Searches directories that are defined in $PATH
$ which ssh
/usr/bin/ssh

Find

More aggressive search tool that can recursively search any given path for various files
$ find / -name nc.exe
/usr/share/windows-binaries/nc.exe
/usr/share/seclists/Web-Shells/FuzzDB/nc.exe

Others

  • Import CA in java store
    sudo keytool -import -alias foo -trustcacerts -keystore cacerts -file cacert.der

curl

display webpage to terminal - text
curl $ip -s -L | html2text -width '99' | uniq

Whats running on a port

ss -lptn 'sport = :443'
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On this page
RTFM
Useful tool help remind you of command syntax
Commands Explained
Kill a process using a port
Append to end of file
sed
Copy output of command to clipboard
Crontab
Extracting archives
Compressing archives
Copy files remotely
File Permissions
Finding Files
Searching within files
Locate, Which, Find
Locate
Which
Find
Others
curl
Whats running on a port