How do I convert a bash array variable to a string delimited with newlines?
Here's a way that utilizes bash parameter expansion and its IFS
special variable.
$ System=('s1' 's2' 's3' 's4 4 4')
$ ( IFS=$'\n'; echo "${System[*]}" )
We use a subshell to avoid overwriting the value of IFS
in the current environment. In that subshell, we then modify the value of IFS
so that the first character is a newline (using $'...'
quoting). Finally, we use parameter expansion to print the contents of the array as a single word; each element is separated by the first charater of IFS
.
To capture to a variable:
$ var=$( IFS=$'\n'; echo "${System[*]}" )
If your bash is new enough (4.2 or later), you can (and should) still use printf
with the -v
option:
$ printf -v var "%s\n" "${System[@]}"
In either case, you may not want the final newline in var
. To remove it:
$ var=${var%?} # Remove the final character of var
You can use printf
to print each array item on its own line:
$ System=('s1' 's2' 's3' 's4 4 4')
$ printf "%s\n" "${System[@]}"
s1
s2
s3
s4 4 4
awk -v sep='\n' 'BEGIN{ORS=OFS="";for(i=1;i<ARGC;i++){print ARGV[i],ARGC-i-1?sep:""}}' "${arr[@]}"
or
perl -le 'print join "\n",@ARGV' "${arr[@]}"
or
python -c 'import sys;print "\n".join(sys.argv[1:])' "${arr[@]}"
or
sh -c 'IFS=$'\''\n'\'';echo "$*"' '' "${arr[@]}"
or
lua <(echo 'print(table.concat(arg,"\n"))') "${arr[@]}"
or
tclsh <(echo 'puts [join $argv "\n"]') "${arr[@]}"
or
php -r 'echo implode("\n",array_slice($argv,1));' -- "${arr[@]}"
or
ruby -e 'puts ARGV.join("\n")' "${arr[@]}"
that's all I can remind so far.