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How to remove new line from variable?

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# 1  
Old 04-20-2013
How to remove new line from variable?
I have following codes:

Code:
~$ var_1="ABC"
~$ echo $var_1 | wc -m
4
~$ echo -n $var_1 | wc -m
3
~$ var_2=`echo -n $var_1`
~$ echo $var_2
ABC
~$ echo $var_2 | wc -m
4
~$

I would suppose the last command
Code:
~$ echo $var_2 | wc -m

would give 3; but apparently, var_2 still has the new line character and has 4 character in total.


So how to remove this new line character from a variable? Thanks.
# 2  
Old 04-20-2013
The variable does not have a newline.

The echo command adds the newline, which "wc -m" counts. That's why you get a different count with "echo -n", which does not add a newline.
This User Gave Thanks to hanson44 For This Post:
littlewenwen
# 3  
Old 04-20-2013
The echo command writes its argument to standard output, followed by a <newline>. If there are no arguments, only the <newline> is written.
Code:
$ echo | od -c
0000000  \n
0000001

This is why you have to use -n option to suppress the trailing <newline>
Code:
$ echo -n | od -c
0000000

You can also use built-in printf instead:
Code:
$ printf "%s" "$var_1" | wc -m
3

This User Gave Thanks to Yoda For This Post:
littlewenwen
# 4  
Old 04-20-2013
Thank you very much for educating me.

Now suppose I have following codes:

Code:
$ var999=abc$'\n'def$'\n'defabc$'\n'def$'\n'def
$ echo "$var999"
abc
def
defabc
def
def
$

var999 has several new line characters; is there a quick way to find out: how many new line characters (and how may other characters) are in this variable?
# 5  
Old 04-20-2013
That's a little tricky. I would suggest the following as the best simple solution:
Code:
$ var999=abc$'\n'def$'\n'defabc$'\n'def$'\n'def
$ echo -n "$var999" | wc -l
4

Reports the right number of newline characters.

------------------------
Code:
$ var999=abc
$ echo -n "$var999" | wc -l
0

Verifies that works for case where no newlines.

------------------------
Code:
$ var999=abc$'\n'def$'\n'defabc$'\n'def$'\n'def
$ echo -n "$var999" | wc -m
23

Shows the total number of characters in the variable.

-------------------

This can get kind of complicated and confusing. Consider the following, where with the -e option '\n' is translated to newline character:
Code:
$ var999="abc\nabc"
$ echo $var999
abc\nabc
$ echo -e $var999
abc
abc
$ echo $var999 | wc -m
9
$ echo -e $var999 | wc -m
8

This User Gave Thanks to hanson44 For This Post:
littlewenwen
# 6  
Old 04-20-2013
Thank you very much.
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