Bash - 扩展命令参数的变量会导致引用地狱

这是我完成的剧本。非常感谢对我问题的评论者。在你的提示下，我能够取得进步。

就其价值而言，目标是定期备份正在使用 .git 存储库的 /etc 并保留 .git 存储库，但忽略 .gitignore 中的内容etckeeper

一些观察：

• 在为命令构建参数列表时，数组完全是要走的路。
• 使用数组时，shell 会漂亮地用空格引用值。Yo 可以通过在下面的脚本中使用来看到这一点。set -x
• 使用真的很有帮助。set -x
• 当您努力获得某些东西时，shellcheck 是一个了不起的诊断工具。

#!/bin/bash
COMMAND=$(basename "${0}")
SRC="/etc"
BACKUP_DIR="/root/backup prep"
TMP_DIR="${BACKUP_DIR}/tmp"
LOG_DIR="${TMP_DIR}"

if ! sudo -v
then
    echo ${COMMAND} quitting...
    exit 1
fi

SRC=$(realpath "${SRC}") # make relative paths absolute
SRC="${SRC}"/ # force rsync to disallow symlinks to the parent path

# https://www.shellcheck.net/wiki/SC2086
# Note that $( ) starts a new context, and variables in it have to
# be quoted independently
LOG_FILE="${LOG_DIR}/${COMMAND}-$(date +%Y-%b-%d-%H-%M-%S-%N).log"
for DIR in "${BACKUP_DIR}" "${TMP_DIR}" "${LOG_DIR}"
do
    if sudo test ! -d "${DIR}";
    then
        echo Creating "${DIR}"
        sudo mkdir "${DIR}"
    fi
done

RSYNC_OPTS=()

# ------------------------------------
# -------------Testing----------------
# ------------------------------------
#
#--dry-run, -n
#RSYNC_OPTS+=("--dry-run")

# ------------------------------------
# -------------Verbosity--------------
# ------------------------------------
#
# --verbose, -v            increase verbosity
#RSYNC_OPTS+=("--verbose")
# --progress               show progress during transfer
#RSYNC_OPTS+=("--progress")
# --itemize-changes, -i    output a change-summary for all updates
#RSYNC_OPTS+=("--itemize-changes")
# --stats                  give some file-transfer stats
#RSYNC_OPTS+=("--stats")
# --human-readable, -h     output numbers in a human-readable format
RSYNC_OPTS+=("--human-readable")
# --log-file=FILE          log what we're doing to the specified FILE
RSYNC_OPTS+=("--log-file=${LOG_FILE}")
# --log-file-format=FMT    log updates using the specified FMT


# ------------------------------------
# -------------Permissions------------
# ------------------------------------
#
# --owner, -o              preserve owner (super-user only)
RSYNC_OPTS+=("--owner")
# --group, -g              preserve group
RSYNC_OPTS+=("--group")
# --perms, -p              preserve permissions
RSYNC_OPTS+=("--perms")
# --xattrs, -X             preserve extended attributes
RSYNC_OPTS+=("--xattrs")
# --acls, -A               preserve ACLs (implies --perms)
RSYNC_OPTS+=("--acls")

# ------------------------------------
# -------------Times------------------
# ------------------------------------
#
# --times, -t              preserve modification times
RSYNC_OPTS+=("--times")
# --crtimes, -N            preserve create times (newness)
# rsync: This rsync does not support --crtimes (-N)
# RSYNC_OPTS+=("--crtimes")
# --atimes, -U             preserve access (use) times
RSYNC_OPTS+=("--atimes")
# --open-noatime           avoid changing the atime on opened files
RSYNC_OPTS+=("--open-noatime")

# ------------------------------------
# -------------Where------------------
# ------------------------------------
#
# --mkpath                 create the destination's path component
RSYNC_OPTS+=("--mkpath")
# --recursive, -r          recurse into directories
RSYNC_OPTS+=("--recursive")
# --links, -l              copy symlinks as symlinks
RSYNC_OPTS+=("--links")
# Rsync can also distinguish "safe" and "unsafe" symbolic links.  An
# example where this might be used is a web site mirror that wishes to
# ensure that the rsync module that is copied does not include symbolic
# links to /etc/passwd in  the public section of the site.  Using
# --copy-unsafe-links will cause any links to be copied as the file they
# point to on the destination.  Using --safe-links will cause unsafe
# links to be omitted altogether. (Note that you  must  specify --links
# for --safe-links to have any effect.)
# --copy-unsafe-links      where the link would point outside of the new tree, copy the file
RSYNC_OPTS+=("--copy-unsafe-links")
# --hard-links, -H         preserve hard links
RSYNC_OPTS+=("--hard-links")
# --one-file-system, -x    don't cross filesystem boundaries
RSYNC_OPTS+=("--one-file-system")

# ------------------------------------
# -------------Exclusions-------------
# ------------------------------------
#
#--filter=RULE, -f        add a file-filtering RULE
RSYNC_OPTS+=("--filter=dir-merge,p- .gitignore")
# --delete-excluded        also delete excluded files from dest dirs
RSYNC_OPTS+=("--delete-excluded")
#--delete-after           receiver deletes after transfer, not during
RSYNC_OPTS+=("--delete-after")
# --force                  force deletion of dirs even if not empty
RSYNC_OPTS+=("--force")
# --update, -u             skip files that are newer on the receiver
#RSYNC_OPTS=${RSYNC_OPTS}" --update")

# ------------------------------------
# -------------Misc-------------------
# ------------------------------------
#
# --protect-args, -s       no space-splitting; wildcard chars only
# This option sends all filenames and most options to the remote rsync
# without allowing the remote shell  to  interpret  them.
RSYNC_OPTS+=("--protect-args")
# --checksum, -c           skip based on checksum, not mod-time & size
RSYNC_OPTS+=("--checksum")
# --temp-dir=DIR, -T       create temporary files in directory DIR
RSYNC_OPTS+=("--temp-dir=${TMP_DIR}")

#echo sudo rsync "${RSYNC_OPTS[@]}" "'${SRC}'" "'${DEST}'"
#echo
#set -x
sudo rsync "${RSYNC_OPTS[@]}" "${SRC}" "${DEST}"