loop through a string 3

[dbadmin]

Hi,

In my korn shell script I have a string of length 9 characters which I need to loop through and get each character out to do a comparison. I know AWK could do that trick, but any way to do it with SHELL?

Thanks,
dbadmin

 

[PHV]

man expr (the substr operator)

Hope This Helps, PH.
Want to get great answers to your Tek-Tips questions? Have a look at FAQ219-2884 or FAQ181-2886

 

[dbadmin]

Thank you! PHV

dbadmin

 

[feherke]

Hi

I found [tt]expr[/tt] abit slow. You can cycle through the characters with [tt]while[/tt] and [tt]read[/tt].

echo -n "abcdefghi" | \
while read -n 1 c; do
  [[ "$c" = [aeiou] ]] && echo -n "vowel : "
  echo "- $c"
done

I tested it with [tt]bash[/tt], but works in [tt]sh[/tt] compatibility mode, so should work on [tt]ksh[/tt] too.

Feherke.

http://rootshell.be/~feherke/

 

[PHV]

so should work on ksh too
Not on mine (as I expected ...)
-n is not a standard option for the read builtin.

 

[feherke]

Hi

Uff. Thanks PHV. Seems that I really need to install [tt]ksh[/tt]. In my distribution's CD is only [tt]dpksh[/tt] 5.2.14 ( Public Domain Korn Shell ). Ok, I know, that is just a "fake" one, but what do you think, could be significant differences between that and the original [tt]ksh[/tt] ?

Feherke.

http://rootshell.be/~feherke/

 

[Annihilannic]

pdksh should be fine, I have only noticed minor differences to "standard" ksh. The ones I can recall are:

pdksh supports brace expansion, Solaris ksh doesn't.

[tt]pdksh-5.2.14-22 $ echo blah{1,2,3}
blah1 blah2 blah3
pdksh-5.2.14-22 $

Solaris 8 ksh $ echo blah{1,2,3}
blah{1,2,3}
Solaris 8 ksh $[/tt]

In pdksh, variables read in a pipeline are not inherited by the parent shell. This may be due to Linux' handling of pipelines rather than pdksh itself... bash behaves in the same way:

[tt]pdksh-5.2.14-22 $ echo "blah" | read n ; echo $n

pdksh-5.2.14-22 $

Solaris 8 ksh $ echo "blah" | read n ; echo $n
blah
Solaris 8 ksh $[/tt]

pdksh doesn't support process substitution, which I really miss!:

[tt]pdksh-5.2.14-22 $ diff <(echo one) <(echo two)
ksh: syntax error: `(' unexpected
pdksh-5.2.14-22 $

Solaris 8 ksh $ diff <(echo one) <(echo two)
1c1
< one
---
> two
Solaris 8 ksh $[/tt]

These differences could be because Sun have stuck with the ksh88 standard and pdksh uses ksh93... or something? I haven't checked. Visit

http://kornshell.com/

for the lowdown from the creator of ksh.

Annihilannic.

 

[Annihilannic]

Interesting! I just downloaded ksh.2005-02-02.linux.i386 from Kornshell.com to a Linux system and it passed all three of these tests, so perhaps that's what you (and I!) should use:

[tt]ksh.2005-02-02.linux.i386 $ echo blah{1,2,3}
blah1 blah2 blah3
ksh.2005-02-02.linux.i386 $ diff <(echo one) <(echo two)
1c1
< one
---
> two
ksh.2005-02-02.linux.i386 $ echo blah | read n ; echo $n
blah
ksh.2005-02-02.linux.i386 $[/tt]

That proves my theory about Linux pipelines wrong as well...

It's possible that this version not normally included with Linux because it uses the AT&T CPL instead of GPL?

Annihilannic.

 

[feherke]

Hi

Thanks Annihilannic. Now I know that I will do this evening.

Feherke.

http://rootshell.be/~feherke/

 

[dbadmin]

Hi all,

Thanks for the replies. I have used substr, but it doesn't look neat, if I could use something like the while loop example... but in ksh it doesn't work.

Thanks,
dbadmin

 

[p5wizard]

not at a shell prompt right now, but this is how I would try it:

echo "abcdefgh"|fold -w1|while read char
do
echo $char
done

HTH,

p5wizard

 

[Annihilannic]

Another idea:

for char in $(echo abcdefgh | sed 's/\(.\)/\1 /g')
do
    echo $char
done

Annihilannic.