iOS/sh: Extract sub-libraries from a given library without access to source code to avoid namespace clashes

strip-lib.sh

#!/bin/zsh

# We at WeltN24 were facing the problem that two libraries that we integrated
# in our iOS project, used the same sub-library which resulted in naming
# conflicts due to the non-existing namespaces in Swift.
#
# If you know what you are doing you can try to solve this conflict by
# extracting the shared sub-library from one of the libraries you want to
# integrate. You can even do this if you don't have access to the source code
# using the lipo (create or operate on universal files) and ar (create and
# maintain library archives) commands.
#
# Why you should know what you are doing?
# Manipulating unknown archives can result in unforseen effects because of the
# fact that you don't know anything about how the provider of the archive uses
# the sub-library, which version of the library was used or if the source
# code of the library was manipulated. So...
# You should know what you are doing manipulting archives :)
#
# The script is processing the files in following order:
# 1. Extracting architecture slices of multi-architecture file $src_lib
# 2. Excluding library archives which match regular expression $reg_exp_remove
# 3. Writing new multi-architecture file $dst_lib
#
# Usage example:
# ./strip-lib.sh sourceLib.a targetLib.a "MyRegularExpression"
#
# Initial script and bash brain: https://github.com/bonkey
# Generalization and eager padawan: https://github.com/pkcpkc (Paul.Hackenberger@weltn24.de)

test $# -ne 3 && echo "strip-lib.sh <sourceLibrary.a> <targetLibrary.a> <regExpRemove>" && exit 1

tmp_prefix="strip-tmp-"
src_lib=$1
dst_lib=$2
reg_exp_remove=$3

# identify supported architectures
archs=$(lipo -info $src_lib | sed 's/.*: \(.*\)/\1/')
archs_array=("${(@s/ /)archs}")

replace_args=()

for arch in $archs_array ; do
	thin_lib=${tmp_prefix}${arch}.a
	lipo $src_lib -thin $arch -output $thin_lib
    echo "Removing from $arch:"
    ar -t $thin_lib | grep -E "$reg_exp_remove"
	ar -t $thin_lib | grep -E "$reg_exp_remove" | xargs ar -d $thin_lib
	replace_args=($replace_args -replace $arch $thin_lib)
done

echo "\nWriting $dst_lib."
lipo $src_lib $replace_args -output $dst_lib

echo "\nRemoving tmp files."
for arch in $archs_array ; do
	rm ${tmp_prefix}${arch}.a
done