Bash – How to Join an Array of Strings with Spaces

arraybashquotingshell-script

My bash script:

#!bin/bash
MY_ARRAY=("Some string" "Another string")
function join { local IFS="$1"; shift; echo -e "$*"; }
join "," ${MY_ARRAY[@]}

I want the output to be:
Some string,Another string.

Instead, I get Some,string,Another,string.

What must I change to get the result I want?

Best Answer

My modified version of your script:

#!bin/bash
my_array=("Some string" "Another string")
my_join() {
  [ "$#" -ge 1 ] || return 1
  local IFS="$1"
  shift
  printf '%s\n' "$*"
}
my_join , "${my_array[@]}"

Notes:

Don't use uppercase variable names
- See Are there naming conventions for variables in shell scripts?
join is a standard tool. Use a different name.
Use quoting
- See Why does my shell script choke on whitespace or other special characters?
Use printf, not echo
- See Why is printf better than echo?

Related Solutions

Bash : Native way to get rid of quotation around each array member

This might work:

in_file=./data
vector=($(./readdata.sh 0 $in_file))
for index in ${!vector[@]}
do
    echo ${vector[index]//\"/}
done

Ref: http://www.tldp.org/LDP/abs/html/refcards.html#AEN22828

Bash Arguments – Joining Arguments into a Single String with Spaces

I believe that this does what you want. It will put all the arguments in one string, separated by spaces, with single quotes around all:

str="'$*'"

$* produces all the scripts arguments separated by the first character of $IFS which, by default, is a space.

Inside a double quoted string, there is no need to escape single-quotes.

Example

Let us put the above in a script file:

$ cat script.sh 
#!/bin/sh
str="'$*'"
echo "$str"

Now, run the script with sample arguments:

$ sh script.sh one two three four 5
'one two three four 5'

This script is POSIX. It will work with bash but it does not require bash.

A variation: concatenating with slashes instead of spaces

We can change from spaces to another character by adjusting IFS:

$ cat script.sh 
#!/bin/sh
old="$IFS"
IFS='/'
str="'$*'"
echo "$str"
IFS=$old

For example:

$ sh script.sh one two three four       
'one/two/three/four'