Shell Script split concatenate and re-use

Question

In Shell script I want to achieve something like below:

str="india,uk,us,uae"

I want to split it and concatenate each item as below and assign to some variable

newstr = '-myParam="india" -myParam="uk" -myParam="us" -myParam="uae"'

so that I can use above concatenated string in my next command as below

curl "admin/admin" "localhost" $newstr.

I found a way using local IFS and for loop but the variable updated inside loop is not retaining value outside of loop because it runs in a separate bash.

Michael Vehrs · Accepted Answer · 2016-05-19 07:22:54Z

3

str="india,uk,us,uae"
var=-myparam=\"${str//,/\" -myparam=\"}\"
echo $var

answered May 19, 2016 at 7:22

Michael Vehrs

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2 Comments

Jeffrey Cash Over a year ago

I believe this is the best and simplest way to go about it

Scott Yang Over a year ago

I believe this is the simplest and shortest answer. But could you give a little explanation when you have time? Thanks

Community · Accepted Answer · 2017-05-23 12:31:46Z

2

Read the params into an array:

IFS=, read -a params <<< "$str"

And then loop through them and store the command in an array:

for i in "${params[@]}"; do
   command+=(-myparam=\"$i\")
done

Now you can expand it using printf "${command[@]}":

$ printf "%s " "${command[@]}"
-myparam="india" -myparam="uk" -myparam="us" -myparam="uae"

That is, now you have to say:

curl "admin/admin" "localhost" "${command[@]}"

This is based on this answer by chepner: command line arguments fed from an array.

edited May 23, 2017 at 12:31

CommunityBot

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answered May 19, 2016 at 6:25

fedorqui

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6 Comments

Benjamin W. Over a year ago

It it weren't for the quotes, we could use "${params[@]/#/-myparam=}".

rici Over a year ago

It seems unlikely to me that OP really wants those quotes. But there aren't enough details to hazard a definite opinion. The array substitution suggestion has lots of merit.

Ronnie Over a year ago

IFS=, read -a params <<< "$str" will reset the delimeter globally or only for this statement ?

fedorqui Over a year ago

@Ronnie just for this statement. You can test by saying IFS=, read -a params <<< "a,b,c" and then read -a params <<< "a,b,c". After each one, execute printf "%s\n" "${params[@]}". Prepending IFS to a command makes it affect just the scope of the command.

Ronnie Over a year ago

@BenjaminW. You were right. I did not want the quotes and used the one line that you mentioned which solved my other issues with for loop. :)

|

sjsam · Accepted Answer · 2016-05-19 07:14:03Z

0

Below code would do :

$ str="india,uk,us,uae"
$ newstr=$(awk 'BEGIN{RS=","}{printf "-myParam=\"%s\" ",$1}' <<<"$str")
$ echo "$newstr"
-myParam="india" -myParam="uk" -myParam="us" -myParam="uae"

Also when you pass new string as parameter to curl, double quote it to prevent word splitting and globbing, so do :

curl "admin/admin" "localhost" "$newstr"

Note: <<< or herestring is only supported in a few shells (Bash, ksh, or zsh) if I recall correctly. If your shell does not support it use echo,pipe combination.

edited May 19, 2016 at 7:14

answered May 19, 2016 at 6:26

sjsam

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Jeffrey Cash · Accepted Answer · 2016-05-19 11:14:28Z

0

IFS=',' read -ra a <<< "${str//,/\",}";
curl "admin/admin" "localhost" "${a[@]/#/ -myParam=\"}\""

Explanation:

Starting with:

str="india,uk,us,uae";

Next, split the string into an array, using parameter substitution to insert " before each comma:

IFS=',' read -ra a <<< "${str//,/\",}";

Finally, we can get newstr through parameter substitution (while also appending the final "):

newstr="${a[@]/#/ -myParam=\"}\"";

newstr is now set to '-myParam="india" -myParam="uk" -myParam="us" -myParam="uae"'. We can skip the previous step and go straight to:

curl "admin/admin" "localhost" "${a[@]/#/ -myParam=\"}\""

edited May 19, 2016 at 11:14

answered May 19, 2016 at 10:55

Jeffrey Cash

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