Appending argv entries to an array (dynamically populating an array) in bash

Question

I'm trying to append content from the argument list ("$@"), excluding $1 and also any value starting with a dash, to an array in bash.

My current code follows, but doesn't operate correctly:

BuildTypeList=("armv7" "armv6")
BuildTypeLen=${#BuildTypeList[*]}

while [ "$2" != "-*" -a "$#" -gt 0 ]; do
    BuildTypeList["$BuildTypeLen"] = "$2"
    BuildTypeLen=${#BuildTypeList[*]}
    shift
done

My intent is to add content to BuildTypeList at runtime, rather than defining its content statically as part of the source.

Solution 1

It's simpler to just iterate over all the arguments, and selectively append them to your list.

BuildTypeList=("armv7" "armv6")
first_arg=$1
shift;

for arg in "$@"; do
    [[ $arg != -* ]] && BuildTypeList+=( "$arg" )
done

# If you really need to make sure all the elements
# are shifted out of $@
shift $#

Solution 2

Append to an array with the += operator:

ary=( 1 2 3 )
for i in {10..15}; do
    ary+=($i)
done
echo "${ary[@]}" # => 1 2 3 10 11 12 13 14 15

Solution 3

There is a plenty of manuals on this subject. See http://www.gnu.org/software/bash/manual/html_node/Arrays.html, for example. Or http://mywiki.wooledge.org/BashGuide/Arrays, or http://www.linuxjournal.com/content/bash-arrays.

Comments

[chepner]

Bash has supported simple arrays for a very long time; bash 2.0, released in the mid 90s, supported them. I hope no one is using a version that doesn't.

[glenn jackman]

make sure you quote "$arg" when you append it to the array.

[Charles Duffy]

Please don't suggest the ABS as a documentation source -- it's out-of-date and often has advice that's flat wrong. mywiki.wooledge.org/BashGuide is more actively supported and maintained.

[Qnan]

@CharlesDuffy might be, I just picked the top link from Google, mostly because pointing to lmgtfy is not too constructive. The point is that there're numerous resources on the subject.