setup.sh

@@ -1,5 +1,19 @@
 #!/bin/bash
 
+# Whatever comes in on file descriptor (FD) 3 gets redirected to where file
+# descriptor 1 is pointing. File descriptor 1 points to stdout so when we
+# output-redirect something into FD 3 it shows up on stdout. We can use this
+# to produce arbitrary logging output inside a subshell like so:
+#
+# function my_func () {
+#     some_command "${1:?}"
+#     >&3 echo 'A log message'
+# }
+#
+# var="$(my_func arg_1)"
+#
+# Here "${var}" will only capture the output of some_command "${1:?}". It
+# will not capture 'echo' which will instead show up on our stdout/FD 1.
 exec 3>&1
 
 declare this_script_url
@@ -250,7 +264,7 @@ function setup_zpool () {
         export_pool
         import_pool
     else
-        printf -- '%s\n' 'A zpool already exists, that is unexpected. Cowardly exiting 1 ...'
+        >&3 printf -- '%s\n' 'A zpool already exists, that is unexpected. Cowardly exiting 1 ...'
         exit 1
     fi
 }
@@ -299,7 +313,7 @@ function prepare_zfsbootmenu_efi_bin_pkg () {
     mount --bind '/mnt/efi' '/efi'
     pushd "${git_zbm_efi_bin_dir}"
     sudo -u 'arch' makepkg -s || {
-        printf -- '%s\n' 'Failed building zfsbootmenu-efi-bin package. Exiting ...'
+        >&3 printf -- '%s\n' 'Failed building zfsbootmenu-efi-bin package. Exiting ...'
         exit 77
     }
     popd
@@ -310,7 +324,7 @@ function prepare_zfsbootmenu_efi_bin_pkg () {
     package_file="$(basename "${package_file_abs}")"
     mkdir -p "${chroot_pacman_cache_dir}"
     rsync -av "${package_file_abs}" "${chroot_pacman_cache_dir}"'/'"${package_file}" || {
-        printf -- '%s\n' 'Failed rsyncing zfsbootmenu-efi-bin package file into chroot. Exiting ...'
+        >&3 printf -- '%s\n' 'Failed rsyncing zfsbootmenu-efi-bin package file into chroot. Exiting ...'
         exit 77
     }
     export ZFSBOOTMENU_EFI_BIN_PKG_PATH="${pacman_cache_dir}"'/'"${package_file}"
@@ -539,7 +553,7 @@ function paru_install () {
     [[ "${1}" ]] && while :; do
         case "${1}" in
             -[[:alnum:]]*)
-                printf -- '%s\n' \
+                >&3 printf -- '%s\n' \
                     'Short-form argument '"'${1}'"' not supported for function '"'${FUNCNAME[0]}()'"'. Only known accepted argument' \
                     'is '"'"'--replace-conflicting'"'"' without a value given. Exiting ...'
                 exit 77
@@ -550,7 +564,7 @@ function paru_install () {
                 continue
                 ;;
             --*)
-                printf -- '%s\n' \
+                >&3 printf -- '%s\n' \
                     'Long-form argument '"'${1}'"' not supported for function '"'${FUNCNAME[0]}()'"'. Only known accepted argument' \
                     'is '"'"'--replace-conflicting'"'"' without a value given. Exiting ...'
                 exit 77
@@ -565,7 +579,7 @@ function paru_install () {
                 ;;
             esac
     done || {
-        printf -- '%s\n' \
+        >&3 printf -- '%s\n' \
             'No argument '"'${1}'"' given for function '"'${FUNCNAME[0]}'"'. Exiting ...'
         exit 77
     }