Split a file into named files

codesplit.sh

#!/bin/bash

# Given a text file like this:
#  /* HEADER */
#  import x
#  import y
#  /* END HEADER */
#  ...code...
#  /* TO: codeFile.swift */
#  ...more code...
#  /* DONE */
#  ...yet more code...
#  /* TO: codeFile2.swift */
#  ...even more code...
#  /* DONE */
#  * APPEND: codeFile.swift */
#  ...yay more code...
#  /* DONE */
#
# Output will be 2 files , 'codeFile.swift' and 'codeFile2.swift' with content:
#     codeFile.swift
#     --------------
#     import x
#     import y
#     ...more code...
#     ...yay more code...
#
#     codeFile2.swift
#     ---------------
#     import x
#     import y
#     ...even more code...
#
#
# The original file minus the moved sections is output to the terminal. Note that the header remains.
#     Terminal output
#     ---------------
#     import x
#     import y
#     ...code...
#     ...yet more code...
#
#
# - Original file is NOT changed
# - TO: files must be unique, any existing file is deleted.  Use APPEND: to add to an existing file (which could be
#     created by an earlier TO:)

FILENAME=$1
awk -F' ' 'BEGIN{file="";pr=1}; /\/\* HEADER/{system("rm -f _header"); file="_header";pr=0}; /\/\* TO:/{file=$3; pr=0;system("rm -f " file); system("cat _header > " file)}; /\/\* APPEND:/{file=$3;pr=0}; /\/\* DONE/{file="";pr=0};/\/* END HEADER/{file="";pr=0};{if (file!="" && pr==1) {print $0  >> file; if (file=="_header") {print $0}} else if (file=="" && pr==1) { print $0};; pr=1}' $FILENAME