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problem with for loop and a variable with spaces...Hi

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Top Forums Shell Programming and Scripting problem with for loop and a variable with spaces...Hi
# 1  
Old 04-20-2010
Question problem with for loop and a variable with spaces...Hi
Hi there,

I don't understand the following behavior:
Code:
toto:~$ for word in un "deux trois"; do echo $word; done
un
deux trois
toto:~$ sentence='un "deux trois"'
toto:~$ for word in $sentence; do echo $word; done
un
"deux
trois"
toto:~$ sentence="un 'deux trois'"
toto:~$ for word in $sentence; do echo $word; done
un
'deux
trois'

Why is the word with a space split in two parts even though it is surrounded by quotes in the variable $sentence?
Is there any way to get the same behavior with a variable and with an explicit string?

Thanks for your help.
Santiago
# 2  
Old 04-20-2010
Hi.

Unless you quote $sentence itself in your for loop, it's still just a collection of words each individually assigned to $word.

Code:
$ sentence="un 'deux trois'"
$ for word in "$sentence"; do echo "$word"; done
un 'deux trois'

# 3  
Old 04-20-2010
... and if you quote $sentence, there's no point in using a loop, since without field splitting there will always be just one word after the parameter expansion Smilie

Quote characters stored in a variable are not special in any way. The variable's expansion occurs after the shell has identified quoted strings.
# 4  
Old 04-20-2010
Quote:
Originally Posted by alister
... and if you quote $sentence, there's no point in using a loop, since without field splitting there will always be just one word after the parameter expansion Smilie
Of course Smilie But I suppose if there were more than one "sentence" it would hold water!
# 5  
Old 04-21-2010
Hi all and thanks for your cooperation.
I think I didn't express myself correctly.

What I'm expecting is to have the sentence un "deux trois" split in two words: un and deux trois.

It's easy to achieve using an explicit string. But is there any way I can do that with the sentence in a variable?

Thanks
Santiago
# 6  
Old 04-21-2010
Code:
$ eval "for word in $sentence; do echo \$word; done"
un
deux trois

As always, eval should not be used on untrusted, unsanitized input.

Regards,
Alister
# 7  
Old 04-21-2010
Some shells support arrays.

For example zsh, bash and ksh93 support this syntax:

Code:
sentence=(un "deux trois")
for w in "${sentence[@]}"; do
  printf '%s\n' "$w"
done

With the Bourne shell, you can use something like this (you'll loose any previously set positional parameters):

Code:
set -- un "deux trois"
for w in "$@"; do
  printf '%s\n' "$w"
done

Some shells support the following shortcut in this context:

Code:
set -- un "deux trois"
for w; do
  printf '%s\n' "$w"
done
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