Re: [opensuse] BASH - rankinism - best way to trim string and add ellipses (or other char)?

7 Dec 2011

      On 12/03/2011 12:36 PM, Martti Laaksonen wrote:
...
[[ ${#str} -gt ${lim} ]]&&
   {
     begin=${str:0:$((lim-rem))};
     end=${str:$((lim-rem)):${rem}};
     echo ${begin}${end//?/${char}};
   } || echo "${str}"
OK,

   That is pretty darn slick! Thanks Martti. I wouldn't have thought about 
string substitution using a single char wildcard as the substring no matter 
how many times I looked at ${string//substring/replacement} :) Now the 
question becomes -- which takes less clock cycles? ANSWER - both so close it's 
hard to call even with 100 repeated calls.

   For those interested a brief synopsis of the testing was:

   Hmm... elm.sh=Martti's way; eld.sh=David's way (first run nothing in cache):

10:15 providence:~/scr/dev> time sh elm.sh my-very-long-string-of-stuff 24 4 +
my-very-long-string-++++

real    0m0.010s
user    0m0.003s
sys     0m0.003s

10:17 providence:~/scr/dev> time sh eld.sh my-very-long-string-of-stuff 24 4 +
my-very-long-string-++++

real    0m0.011s
user    0m0.007s
sys     0m0.003s

   Martti's wins -- now let's run it a second time with the files in cache:

10:17 providence:~/scr/dev> time sh elm.sh my-very-long-string-of-stuff 24 4 +
my-very-long-string-++++

real    0m0.010s
user    0m0.007s
sys     0m0.003s

10:19 providence:~/scr/dev> time sh eld.sh my-very-long-string-of-stuff 24 4 +
my-very-long-string-++++

real    0m0.010s
user    0m0.003s
sys     0m0.003s

   Now -- I just don't get it -- results are opposite. (although the times are 
both so small as to be in the noise) Oh well, I still like the elegance of the 
string substitution that eliminates the for loop. OK, what about 100 times:

time for ((i=0;i<100;i++)); do sh elm.sh my-very-long-string-of-stuff 24 4 +; done

real    0m1.021s
user    0m0.587s
sys     0m0.220s

time for ((i=0;i<100;i++)); do sh eld.sh my-very-long-string-of-stuff 24 4 +; done

real    0m1.005s
user    0m0.577s
sys     0m0.220s

   For those interested, the test code was:

10:19 providence:~/scr/dev> cat elm.sh
#!/bin/bash

function emartti() {

   # validate sufficient parameters passed
   [[ -z "$1" ]] || [[ -z "$2" ]] && { echo "ERROR: Insufficient input in fxn 
emartti"; return 1; }

   str="${1}"
   lim="${2}"
   rem=${3:-3}
   char=${4:-.}

   # validate integers
   [ $lim -eq $lim ] 2>/dev/null || return 1
   [ $rem -eq $rem ] 2>/dev/null || return 1

   [[ ${#str} -gt ${lim} ]] &&
   {
     begin=${str:0:$((lim-rem))};
     end=${str:$((lim-rem)):${rem}};
     echo ${begin}${end//?/${char}};
   } || echo "${str}"
}

[[ -n $4 ]] && {
   emartti "$1" "$2" "$3" "$4"
   exit 0
}

[[ -n $3 ]] && {
   emartti "$1" "$2" "$3"
   exit 0
}

[[ -n $2 ]] && {
   emartti "$1" "$2"
   exit 0
}

   [[ -z $1 ]] || [[ -z $2 ]] && { echo "ERROR: Insufficient input in fxn
emartti"; exit 1; }

exit 0

10:22 providence:~/scr/dev> cat eld.sh
#!/bin/bash

ellipse() {

   # validate sufficient parameters passed
   [[ -z "$1" ]] || [[ -z "$2" ]] && { echo "ERROR: Insufficient input in fxn 
ellipse"; return 1; }

   str="$1"
   lim="$2"
   end=${3:-3}
   chr=${4:-.}

   # validate integers
   [ $lim -eq $lim ] 2>/dev/null || return 1
   [ $end -eq $end ] 2>/dev/null || return 1

   [[ ${#str} -gt $lim ]] &&
   {
     newstr=${str:0:$((lim-end))}
     for((i=$((lim-end));i<$lim;i++)); do
       newstr=${newstr}${chr}
     done

     echo "$newstr"
   } || {
     echo "$str"
   }
}

[[ -n $4 ]] && {
   ellipse "$1" "$2" "$3" "$4"
   exit 0
}

[[ -n $3 ]] && {
   ellipse "$1" "$2" "$3"
   exit 0
}

[[ -n $2 ]] && {
   ellipse "$1" "$2"
   exit 0
}

   [[ -z $1 ]] || [[ -z $2 ]] && { echo "ERROR: Insufficient input in fxn
ellipse"; exit 1; }

exit 0

-- 
David C. Rankin, J.D.,P.E.
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