Patterns

som_kurian · 11-16-2007, 02:48 AM

Hi guys

I want to get the output of shell script as

1
12
123
1234
12345
123456
........

what I did is
for (( a=1; a <= 9; a++ ))
do
for (( b=a; b <= a; b++ ))
do
echo :$b\n"
done
done

But I am not getting the desired output

Rawoof · 11-16-2007, 04:13 AM

Quote:

Originally Posted by som_kurian

Hi guys

I want to get the output of shell script as

1
12
123
1234
12345
123456
........

what I did is
for (( a=1; a <= 9; a++ ))
do
for (( b=a; b <= a; b++ ))
do
echo :$b\n"
done
done

But I am not getting the desired output

IN the second for loop variable b must be assigned 1 instead of a to get
the required output

Hobbletoe · 11-16-2007, 07:54 AM

Wouldn't one loop do the trick?

Code:

for i in $(seq 1 9)
do
 j=${j}${i}
 echo ${j}
done

archtoad6 · 11-18-2007, 08:28 AM

If the ending digit is fixed, have a look at brace expansion (find it in man bash):

Code:

for i in {1..6}
do
 j=${j}${i}
 echo ${j}
done

It's more compact, & possibly faster, than $(seq 1 6).

Using seq & tr inside the loop can eliminate a line from it:

Code:

for X in {1..6}
do echo $(seq 1 $X)  | tr -d ' '
done

If you're going to seq in the loop definition, you might as well get the benefit of variable limits:

Code:

n=6
for X in $(seq 1 $n)
do echo $(seq 1 $X)  | tr -d ' '
done

ghostdog74 · 11-18-2007, 10:03 PM

Code:

awk 'BEGIN {
    a=1
    print 1
    for(i=2;i<=6;i++){
        printf "%s%s\n", a,i
        a=a i
    }
}'

output:

Code:

#./test.sh
1
12
123
1234
12345
123456

som_kurian · 11-23-2007, 03:20 AM

can anyone reply what is wrong in this program

for (( a=1; a <= 9; a++ ))
do
for (( b=1; b <= a; b++ ))
do
echo "$b\n"
done
done

The output I am getting is
1\n
1\n
2\n
1\n
2\n
3\n
1\n
2\n
3\n
4\n

bigearsbilly · 11-23-2007, 03:25 AM

echo on bash doesn't do "\n"
you need echo -e
or, leave it off as it does one anyway,
or use printf

get in the habit of reading the manual

som_kurian · 11-23-2007, 04:21 AM

Thank you dear "bigearsbilly"...I understand...I will try some other way.Thanks for your advice

archtoad6 · 11-24-2007, 07:33 AM

RT

M for echo -- the option you want is "-n'.

While I consider them too long & complex to be considered elegant, your nested loops can be easily fixed:

Code:

for (( a=1; a <= 9; a++ ))
do
  for (( b=1; b <= a; b++ ))
  do
     echo -n "$b"
  done
  echo
done

Timing
Just for fun, I checked the time used by the various techniques suggested using time. To get some to register a measurable time, I had to push n/a/i to 99.

The results surprised me: The hands down winner was:

Code:

for ((i=1;i<=99;i++))
do
   j=${j}${i}
   echo ${j} 
done

2nd:

Code:

for i in {1..99}
do
   j=${j}${i}
   echo ${j} 
done

3rd was my repaired ver. of the orig. code.

So much for "elegance" when production matters.

som_kurian · 12-05-2007, 11:37 PM

Thank you very much dear "archtoad6".......I was looking for this answer...Thank you once again for everyone who helped me...I got the output....YOU GUYS ROCK!!!!!!

matthewg42 · 12-06-2007, 01:46 AM

Now the awk and shell script is out of the way, we can have some fun with Perl:

Code:

$ perl -e 'map {printf "%s\n",$s.=$_;} (1..6);'

bigearsbilly · 12-06-2007, 04:20 AM

darn it, a bit longer matthew

Code:

perl -l012 -e 'foreach (1..6) { push @L, $_;print @L}'

enemorales · 12-06-2007, 08:43 AM

I took the three scripts from archtoad6's post and run the same tests, but got different results. After several running and looking at the times, the three scripts were very close to each other (in my --slow-- machine, about 0.050 s).

Then, only for curiosity, I took one the scripts and changed it a "little":

Code:

for ((i=1;i<=99;i++))
do
   j=${j}${i}
   echo "echo \"${j}\""
done

to create a new script with goes like

Code:

echo "1"
echo "12"
echo "123"
...

Which turned to be slower (first 2 runs), but after the third one it was slightly faster

( about 0.040s), some caching probably helping...

bigearsbilly · 12-06-2007, 09:01 AM

well, the perl thrashes the bash up to 99, but make it 999 and the perl loses.
I guess it is constructing a large list.

punnu6789 · 06-29-2023, 02:04 PM

read n
for (( i=1 ; i<=$n ; i++ ))
do
seq -s " " $i
done