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commandlinefu.com is the place to record those command-line gems that you return to again and again.

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May 19, 2015 - A Look At The New Commandlinefu
I've put together a short writeup on what kind of newness you can expect from the next iteration of clfu. Check it out here.
March 2, 2015 - New Management
I'm Jon, I'll be maintaining and improving clfu. Thanks to David for building such a great resource!
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awk, bash, curl, find, grep, Linux, sed
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Maintained by Jon H.

Site originally by David Winterbottom (user root).

Psst. Open beta.

Wow, didn't really expect you to read this far down. The latest iteration of the site is in open beta. It's a gentle open beta-- not in prime-time just yet. It's being hosted over at UpGuard (link) and you are more than welcome to give it a shot. Couple things:

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Your feedback is appreciated via the form on the beta page. Thanks! -Jon & CLFU Team

Commands using cat from sorted by
Terminal - Commands using cat - 441 results
cat *.txt >output.txt
2010-04-16 14:06:47
User: jmcantrell
Functions: cat
Tags: bash Linux
2
Up
Down
Combining text files into one file
Comments (1) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
ls | grep *.txt | while read file; do cat $file >> ./output.txt; done;
2010-04-16 13:19:38
User: octopus
Functions: cat grep ls read
Tags: bash Linux
-15
Up
Down
Combining text files into one file
Comments (1) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
if cat /proc/cpuinfo | grep " lm " &> /dev/null; then echo "Got 64bit" ; fi
2010-04-10 15:31:58
User: xeor
Functions: cat echo grep
Tags: cpuinfo
4
Up
Down
Determine whether a CPU has 64 bit capability or not

Check if you have 64bit by looking for "lm" in cpuinfo. lm stands for "long mem". This can also be used without being root.

Comments (3) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
cat /etc/apache2/sites-enabled/* | egrep 'ServerAlias|ServerName' | tr -s ' ' | sed 's/^\s//' | cut -d ' ' -f 2 | sed 's/www.//' | sort | uniq
2010-04-08 15:50:34
User: chronosMark
Functions: cat cut egrep sed sort tr
2
Up
Down
Get Unique Hostnames from Apache Config Files

Get a list of all the unique hostnames from the apache configuration files. Handy to see what sites are running on a server. A slightly shorter version.

Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
cat /etc/apache2/sites-enabled/* | egrep 'ServerAlias|ServerName' | tr -s " " | sed 's/^[ ]//g' | uniq | cut -d ' ' -f 2 | sed 's/www.//g' | sort | uniq
2010-04-08 08:51:17
User: chronosMark
Functions: cat cut egrep sed sort tr uniq
0
Up
Down
Get Unique Hostnames from Apache Config Files

Get a list of all the unique hostnames from the apache configuration files. Handy to see what sites are running on a server.

Comments (1) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
cat /proc/acpi/thermal_zone/*/temperature
2010-03-28 01:30:14
User: starchox
Functions: cat
0
Up
Down
Show thermal info

A quick way of know the temperature info.

Show sample output | Comments (0) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
curl -sL xkcd.com | grep '<img [^>]*/><br/>' | sed -r 's|<img src="(.*)" title="(.*)" alt="(.*)" /><br/>|\1\t\2\t\3|' > /tmp/a; curl -s $(cat /tmp/a | cut -f1) | convert - -gravity south -draw "text 0,0 \"$(cat /tmp/a | cut -f2)\"" pdf:- > xkcd.pdf
2010-03-03 03:41:31
User: matthewbauer
Functions: cat cut grep sed
Tags: pdf xkcd caption
6
Up
Down
Save xkcd to a pdf with captions

Saves to a PDF with title and alt text of comic.

As asked for on http://bbs.archlinux.org/viewtopic.php?id=91100

Change xkcd.com to dynamic.xkcd.com/comics/random for a random comic.

Comments (9) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
pdftk A=chapters.pdf B=headings.pdf C=covers.pdf cat C1 B1 A1-7 B2 A8-10 C2 output book.pdf
2010-03-02 16:04:50
User: bw
Functions: cat
7
Up
Down
split and combine different pages from different pdf's

The command shows the real power of the pdftk tool, you can do basically everything you want with multiple pdf's.

In the command a book is created from chapters, headings and covers.

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cat /proc/$(lsof -ti:8888)/cmdline | tr "\0" " "
2010-02-24 17:10:40
User: glaudiston
Functions: cat tr
3
Up
Down
Show the command line of a process that use a specific port (ubuntu)
Comments (2) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
for file in `find . -iname "FILENAME"`; do cat $file | sed "s/SEARCH_STRING/REPLACE_STRING/" > $file.tmp; mv $file.tmp $file; done
2010-02-24 13:46:29
User: unixmonkey6754
Functions: cat file mv sed
-5
Up
Down
a find and replace within text-based files, for batch text replacement, not using perl
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cat authorized_keys_with_broken_lines | sed 's,^ssh,%ssh,' | tr '\n' '\0' | tr '%' '\n' | sed '1d' | sed "/^$/d" > authorized_keys
2010-02-19 08:32:35
User: pepin
Functions: cat sed tr
0
Up
Down
Reconstruct a malformed authorizated_keys for ssh

when someone mail you his ssh public key, and the lines are broken with '\n', you can reconstruct a new file with one key by line with this command.

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echo $(cat file)
2010-02-11 19:07:44
User: tlacuache
Functions: cat echo
2
Up
Down
convert a line to a space
Comments (2) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
cat file | tr '\n' ''
2010-02-11 07:30:29
User: bortoelnino
Functions: cat file tr
4
Up
Down
convert a line to a space
Comments (3) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
#Client# cat "The Meters - People Say.mp3" | nc -vv 192.168.1.100 8080; #Server# nc -vv -l -s 192.168.1.100 -p 8080 | mpg123 -v -
2010-01-30 08:50:17
User: Abiden
Functions: cat mpg123
-3
Up
Down
Pipe music over netcat with mpg123

I think I picked this one up from Hak5 (yeah I know.. kinda lame)

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echo $(( $( cat count.txt | tr "\n" "+" | xargs -I{} echo {} 0 ) ))
2010-01-27 10:02:30
User: glaudiston
Functions: cat echo tr xargs
1
Up
Down
Using numsum to sum a column of numbers.

if you, like me, do not have the numsum, this way can do the same.

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for host in $(cat ftps.txt) ; do if echo -en "o $host 21\nquit\n" |telnet 2>/dev/null |grep -v 'Connected to' >/dev/null; then echo -en "FTP $host KO\n"; fi done
2010-01-26 15:34:18
User: vlan7
Functions: cat echo grep host telnet
Tags: monitoring ftp server
1
Up
Down
Testing ftp server status

I must monitorize a couple of ftp servers every morning WITHOUT a port-scanner

Instead of ftp'ing on 100 ftp servers manually to test their status I use this loop.

It might be adaptable to other services, however it may require a 'logout' string instead of 'quit'.

The file ftps.txt contains the full list of ftp servers to monitorize.

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cat /proc/meminfo
2010-01-22 16:48:03
User: svnlabs
Functions: cat
-1
Up
Down
Get Memeory Info

Get Memeory Info

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nmap -sP <subnet>.* | egrep -o '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+' > results.txt ; for IP in {1..254} ; do echo "<subnet>.${IP}" ; done >> results.txt ; cat results.txt | sort -n -t . -k 1,1 -k 2,2 -k 3,3 -k 4,4 | uniq -u
2010-01-22 00:26:42
User: bortoelnino
Functions: cat echo egrep sort uniq
0
Up
Down
Find unused IPs on a given subnet
Comments (1) | Add to favourites | Report as malicious | Submit alternative | Report as a duplicate
for i in $(ps -ef | awk '{print $2}') ; { swp=$( awk '/Swap/{sum+=$2} END {print sum}' /proc/$i/smaps ); if [[ -n $swp && 0 != $swp ]] ; then echo -n "\n $swp $i "; cat /proc/$i/cmdline ; fi; } | sort -nr
2010-01-22 00:09:46
User: cbrinker
Functions: awk cat echo ps sort
Tags: Linux zsh process swap
0
Up
Down
Linux zsh one-liner to Determine which processes are using the most swap space currently

Col 1 is swapped sum in kb

Col 2 is pid of process

Col 3 is command that was issued

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cat -n <file> | sort -k 2 | uniq -f 1 | sort -n | cut -f 2-
2010-01-21 18:55:58
User: fpunktk
Functions: cat cut sort uniq
4
Up
Down
delete duplicate lines from a file and keep the order of the other lines

i wanted to delete all duplicate lines from .bash_history and keep the order of the other lines.

the command cat's the file and adds line numbers, then sorts by the second column. afterwards uniq omits repeated lines, but skips the first field (the line number). then it sorts by the line numbers and at the end cuts the numbers off.

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# cat file1.mp3 file2.mp3 > file3.mp3
2010-01-17 13:18:34
User: svnlabs
Functions: cat
-4
Up
Down
Merge - Concate MP3 files

cat - concatenate MP3 files and save it...

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(bzcat BZIP2_FILES && cat TEXT_FILES) | grep -E "Invalid user|PAM" | grep -o -E "from .+" | awk '{print $2}' | sort | uniq >> /etc/hosts.deny
2010-01-03 04:41:51
User: jayhawkbabe
Functions: awk cat grep sort uniq
3
Up
Down
Block all IP addresses and domains that have attempted brute force SSH login to computer

Searches all log files (including archived bzip2 files) for invalid user and PAM authentication errors, both of which are indicative of brute force attempts at logging into computer. A list of all unique IP addresses and domain names is appended to hosts.deny. The command (and grep error messages) will work on Mac OS X 10.6, small adjustments may be needed for other OSs.

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ssh HOST cat < LOCALFILE ">" REMOTEFILE
2009-12-22 16:35:34
User: Mandark
Functions: cat ssh
Tags: file transfer
6
Up
Down
Copy a file over SSH without SCP
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ps aux | grep [h]ttpd | cat -n
2009-12-17 20:45:44
User: putnamhill
Functions: cat grep ps
Tags: cat
0
Up
Down
count and number lines of output, useful for counting number of matches

If you're on a system that doesn't have nl, you can use cat -n.

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cat ~/.ssh/id_rsa.pub | ssh <remote_host> "xargs --null echo >> ~/.ssh/authorized_keys"
2009-12-17 15:12:11
User: koushik
Functions: cat ssh
0
Up
Down
Create SSH key exchange from one host to the other

Well its just appending your public key to the remote hosts authorized_keys, but can get messy logging in and out

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