[SOLVED] bash scripting homework question

whizje · 05-02-2012, 05:25 PM

No, but I like Gajovy solution very much and maybe studies the OP the solutions. (And it's a rather simple problem if you cheat homework with this you will only cheat on yourself when you get your exam.)

arungala · 05-02-2012, 10:51 PM

@suicidaleggrol:

x=$@ # copy parameters to variable x
result=$(echo $x | rev | cut -d ' ' -f 2-)
echo $result ${x##*' '}

can u pls explain line by line

arungala · 05-02-2012, 10:54 PM

@TBs:

i'm in training right now ....they give probs for us to solve so that we can get familiar with bash..if u cant why criticize..this forum is for help...i'm not asking anyone to do my homework..my intention is not such...and i've tried rev command..it reverses the whole line..but i want last argument to be same...

i got the answer now..thanks to suicedaleggroll

---------- Post added 05-03-12 at 10:24 AM ----------

thank you so much suicedaleggroll...you've been a great help dude..

arungala · 05-02-2012, 10:57 PM

@suicedaleggroll the thing is when typing 1 2 3 54 5 we get>>>45 3 2 1 5...i dont the the number 54 to be reversed

arungala · 05-02-2012, 11:01 PM

@whizje: i know ddude.i'm not cheating...trying to learn new commands..i think all of u have good experience..i 'mm learning bash since 7 days...so understand if i'm stuck it takes forever...and thank you for ur concern

gajovy · 05-02-2012, 11:25 PM

Quote:

Originally Posted by whizje

Your programs gives problems with more then 10 parameters. A little adaptation.

Code:

#!/bin/bash

if [ $# -gt 0 ]; then
	echo "${@:$#} $@ "| tac -s" " | cut -d " "  -f 2-
	exit 0
else
	echo "please enter some args" >> /dev/stderr
	exit 1
fi

Thanks whizje, I've totally forgoten about variable offsets.

_________________________________

arungala, to complete this task I suggest the following lecture:

man bash
use / to search and search for "parameter:\offset"

man tac
you'll probably find "man cat" helpful too

man cut

If this is a homework, I really suggest reading "man bash" a lot.
If you have to write scripts for a company, find yourself another job before they fire you.

arungala · 05-02-2012, 11:33 PM

i have 3 months..i think i wil learn lot more

whizje · 05-03-2012, 02:07 AM

A somewhat nicer output

Code:

#!/bin/bash
if [ $# -gt 0 ]   # $# is number of parameters if number of parameters is greater then 0 the then part is chosen.
  then
    echo -en "\n ${@:$#} ${@:1:$#-1} " | tac -s" "
# echo output string
# -e see \n as a newline
# -n delete newlines in string
# "\n is a newline
# ${@:$#} string is the $# (number of arguments) of $@ (arguments) As number of arguments is 3 and the arguments are 1 2 34 string becomes 34
# ${@:1:$#-1} string is argument 1 until number of arguments minus 1 As number of arguments is 3 and the arguments are 1 2 34 string becomes 1 2
# in between \n,${@:$#} and ${@:1:$#-1} are spaces and after ${@:1:$#-1} ia a space
# we now have he string it only has to be reversed string is "\n 34 1 2 "
# | pipe symbol use output previous command (echo -en "\n ${@:$#} ${@:1:$#-1} ") as input for next command (tac -s" ")
# tac -s" " reverse the string use space as word separator "\n 34 1 2 " becomes "2 1 34 \n " \n is not printed but interpreted as a newline. 
    exit 0
  else
    echo "please enter some args" >> /dev/stderr
    exit 1
fi

arungala · 05-03-2012, 02:57 AM

Whizje my friend thank you...can u also explain this for better understanding of bash

x=$@ # copy parameters to variable x
result=$(echo $x | rev | cut -d ' ' -f 2-)
echo $result ${x##*' '}

cbtshare · 05-03-2012, 03:37 AM

lmaooo @

Quote:

Originally Posted by TB0ne

If it took you FOUR HOURS to do this, you're in trouble. Also, you say you're working for a 'small company', but I cannot think of ANY reason why a 'company' would need a shell script to do what you're asking for. This is homework, so please be honest about it.

didn't take 4hrs but this works well

...I guess there is a number of ways to do these homework type stuff,just study up on positional parameters and you will be good.

I have the least amount of lines so I win :d :d :d (jk)

Quote:

#!/bin/bash

num=${@:? Please enter some number}

last=${@:$#}
rest=$(echo ${@/$last} | tac -s" ")
echo $(echo $rest $last)

acid_kewpie · 05-03-2012, 04:38 AM

Why are we bothering to ask people not to help others cheat when they just do it anyway?

arungala · 05-03-2012, 04:40 AM

no use explaining you guys..its complicated...thank you for helping anyways

acid_kewpie · 05-03-2012, 04:46 AM

Quote:

Originally Posted by arungala

no use explaining you guys..its complicated...thank you for helping anyways

Well I hope that sums things up for everyone who spoonfed someone their answers and has no idea what the code they are going to submit even does... well done.

arungala · 05-03-2012, 04:48 AM

ok i agree you're the honest god of linux..happy?

whizje · 05-03-2012, 05:32 AM

Code:

X=$@ # copy parameters to string x 
echo $x # output $x
| take output of previous commando as input for next command 
rev # reverse string 
cut -d ' ' -f 2 #use  space as delimiter start field 2 of string until end
result =$( ) # create string and put result in result .
echo # output strings 
$result # inverted string  minus first parameter 
${x##*' '} # delete from string  x from beginning (*' ') words followed by space effectively this is all parameters except last