Numbered string in bash Linux

Question

I want to define numbered string in series in bash such as follows:

String1
String2
String3
String4
String5

What I did till now is as follows which it does not work well.

#!/bin/bash
str_name='String'
for i in `seq 1 5`
do
expr=$(($str_name + $i)) #this part is what I cannot deal with it.
echo $expr
done

Thanks

"it does not work well" - you'd help the guys here by saying what doens't work! f.e.: Error Messages? What is the output you get? — Jeff
– Jeff, Commented Jun 20, 2016 at 23:32

Jonny Henly · Accepted Answer · 2016-06-20 23:36:39Z

1

What you're doing is adding variables in an arithmetic sense. You want to use the following:

expr="${str_name}${i}"

Note: It's not necessary to surround the variables with brackets. I just do it because it's easier to read sometimes, it also keeps me from making stupid mistakes.

To go into more detail, $(...) executes anything between the parentheses in a sub-shell and returns the results. I'm not sure what output you where getting when echoing $expr, but I gather it was an error message. Something like Command String + 1 cannot be found but I really don't know.

edited Jun 20, 2016 at 23:36

answered Jun 20, 2016 at 23:26

Jonny Henly

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2 Comments

gniourf_gniourf Over a year ago

No errors: here it's not about $( ... ) but about $(( ... )), which is an arithmetic expansion, not a command substitution. In OP's case, String is undefined, hence expands to 0 in arithmetic, so the expansion $expr is 1, 2, 3, 4, 5 respectively.

Jonny Henly Over a year ago

You're completely right @gniourf_gniourf - don't know what I was thinking. I'll edit my last paragraph out. Do you mind if I add your comment to my answer, with attribution?

sumitya · Accepted Answer · 2016-06-21 05:27:32Z

0

You even don't require echo in another line. try this.

#!/bin/bash
str_name='String'
for i in `seq 1 5`
do
echo $str_name$i
done

answered Jun 21, 2016 at 5:27

sumitya

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Comments

David C. Rankin · Accepted Answer · 2016-06-21 08:20:27Z

0

Brace Expansion is another manner in which you can iterate over a range:

for i in {1..5}; do
    printf "String%d\n" $i
done

For example:

$ for i in {1..5}; do printf "String%d\n" $i; done
String1
String2
String3
String4
String5

answered Jun 21, 2016 at 8:20

David C. Rankin

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