Another combination of seq and awk. Not very efficient, but sufficiently quick. Show Sample Output
Print a row of characters across the terminal. Uses tput to establish the current terminal width, and generates a line of characters just long enough to cross it. In the example '#' is used.
It's possible to use a repeating sequence by dividing the columns by the number of characters in the sequence like this:
seq -s'~-' 0 $(( $(tput cols) /2 )) | tr -d '[:digit:]'
or
seq -s'-~?' 0 $(( $(tput cols) /3 )) | tr -d '[:digit:]'
You will lose chararacters at the end if the length isn't cleanly divisible.
Show Sample Output
"seq 100" outputs 1,2,..,100, separated by newlines. awk adds them up and displays the sum.
"seq 1 2 11" outputs 1,3,..,11.
Variations:
1+3+...+(2n-1) = n^2
seq 1 2 19 | awk '{sum+=$1} END {print sum}' # displays 100
1/2 + 1/4 + ... = 1
seq 10 | awk '{sum+=1/(2**$1)} END {print sum}' # displays 0.999023
Show Sample Output
Displays six rows and five columns of random numbers between 0 and 1. If you need only one column, you can dispense with the "for" loop. Show Sample Output
print multiple increasing years using cal - calendar -. You can also try
seq Start Increment End
It takes over 5 seconds to scan a single port on a single host using nmap
time (nmap -p 80 192.168.1.1 &> /dev/null)
real 0m5.109s
user 0m0.102s
sys 0m0.004s
It took netcat about 2.5 minutes to scan port 80 on the class C
time (for NUM in {1..255} ; do nc -w 1 -z -v 192.168.1.${NUM} 80 ; done &> /dev/null)
real 2m28.651s
user 0m0.136s
sys 0m0.341s
Using parallel, I am able to scan port 80 on the entire class C in under 2 seconds
time (seq 1 255 | parallel -j255 'nc -w 1 -z -v 192.168.1.{} 80' &> /dev/null)
real 0m1.957s
user 0m0.457s
sys 0m0.994s
unset PROMPT_COMMAND to disable. Show Sample Output
This is a slightly modified version of the knoppix5 user oneliner (https://www.commandlinefu.com/commands/view/24571/draw-line-separator). Show Sample Output
Uses 'seq' with formatting parameter to generate the necessary padded sequence. Change '%02.0f' to how many digits you need (for 3, use %03.0f, etc) and replace 5 & 15 with your desired min and max. Show Sample Output
Nice command to create a list, you can create too with for command, but this is so faster. Show Sample Output
If you want a sequence that can be plotted, do: seq 8 | awk '{print "e(" $0 ")" }' | bc -l | awk '{print NR " " $0}' Other bc functions include s (sine), c (cosine), l (log) and j (bessel). See the man page for details. Show Sample Output
yt2mp3(){ for j in `seq 1 301`;do i=`curl -s gdata.youtube.com/feeds/api/users/$1/uploads\?start-index=$j\&max-results=1|grep -o "watch[^&]*"`;ffmpeg -i `wget youtube.com/$i -qO-|grep -o 'url_map"[^,]*'|sed -n '1{s_.*|__;s_\\\__g;p}'` -vn -ab 128k "`youtube-dl -e ${i#*=}`.mp3";done;}
squeezed the monster (and nifty ☺) command from 7776 from 531 characters to 284 characters, but I don't see a way to get it down to 255. This is definitely a kludge!
Calculate pi from the infinite series 4/1 - 4/3 + 4/5 - 4/7 + ... This expansion was formulated by Gottfried Leibniz: http://en.wikipedia.org/wiki/Leibniz_formula_for_pi I helped rubenmoran create the sum of a sequence of numbers and he replied with a command for the sequence: 1 + 2 -3 + 4 ... This set me thinking. Transcendental numbers! seq provides the odd numbers 1, 3, 5 sed turns them into 4/1 4/3 4/5 paste inserts - and + bc -l does the calculation Note: 100 million iterations takes quite a while. 1 billion and I run out of memory. Show Sample Output
In order to create, let's say, 10 directories with a single process we can use the command:
mkdir test{1,2,3,4,5,6,7,8,9,10}
something extremely boring to type! Why not use seq?
seq -s, 1 10
and use its output inside the curly braces?
The obvious solution
mkdir test{$(seq -s, 1 10)}
is, unfortunately, too naive and doesn't work. The answer is the order of the shell expansions (feature of Bourne Shell, actually), where brace expansion happens before command substitution (according to Bash's manual).
The solution is to put another level of substitution, using the powerful and mystic command eval.
I found the trick in a similar problem in the post at http://stackoverflow.com/questions/6549037/bash-brace-expansion-in-scripts-not-working-due-to-unwanted-escaping
creates 100 directories f(1-100) with a file in each matched to the directory (/f1/myfile1, .. /f98/myfile98,/f99/myfile99/,/f100/myfile100,etc ) Show Sample Output
Ever need to get some text that is a specific number of characters long? Use this function to easily generate it! Doesn't look pretty, but sure does work for testing purposes! Show Sample Output
change the time that you would like to have as print interval and just use it to say whatever you want to Show Sample Output
The example runs 'puppet' in a loop for 10 times, but exits the loop before if it returns 0 (that means "no changes on last run" for puppet).
Useful for download mulitple files Show Sample Output
I can't put the last ^2 with seq, so I reverse it to delete the last +N. So for doing sum(N^2) you have to do sum((N+1)^2). Must be a better way. Show Sample Output
With counter format [001, 002, ..., 999] , nice with pictures or wallpapers collections.
Suppose you have 11 marbles, 4 of which are red, the rest being blue. The marbles are indistinguishable, apart from colour. How many different ways are there to arrange the marbles in a line? And how many ways are there to arrange them so that no two red marbles are adjacent? There are simple mathematical solutions to these questions, but it's also possible to generate and count all possibilities directly on the command line, using little more than brace expansion, grep and wc! The answer to the question posed above is that there are 330 ways of arranging the marbles in a line, 70 of which have no two red marbles adjacent. See the sample output. To follow the call to marbles 11 4: after c=''; for i in $(seq $1); do c+='{b,r}'; done;, $c equals {b,r}{b,r}{b,r}{b,r}{b,r}{b,r}{b,r}{b,r}{b,r}{b,r}{b,r} After x=$(eval echo $c), and brace expansion, $x equals bbbbbbbbbbb bbbbbbbbbbr ... rrrrrrrrrrb rrrrrrrrrrr, which is all 2^11 = 2048 strings of 11 b's and r's. After p=''; for i in $(seq $2); do p+='b*r'; done;, $p equals b*rb*rb*rb*r Next, after y=$(grep -wo "${p}b*" Finally, grep -vc 'rr' Show Sample Output
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