initial commit

LICENSE

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+The MIT License (MIT)
+
+Copyright 2020 "fox"
+
+Permission is hereby granted, free of charge, to any person obtaining a copy of
+this software and associated documentation files (the "Software"), to deal in
+the Software without restriction, including without limitation the rights to
+use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of
+the Software, and to permit persons to whom the Software is furnished to do so,
+subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS
+FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR
+COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER
+IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
+CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

README

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+lyr
+====
+
+an abbreviation of "layer."
+
+maintains a repository of overlayfs upper directories, work directories, and
+mount paths at LYRREPO.  simplifies mounting, unmounting, creating, and
+deleting layers.
+
+62 ELOC.
+
+usage: lyr.sh [command] <layer name>
+
+commands:
+    workdir
+        returns the work directory path for the layer.
+
+    upperdir
+        returns the upper directory path for the layer.
+
+    mountdir
+        returns the mount directory path for the layer.
+
+    mk
+        create a new layer with the given name.
+
+    rm
+        unmount and delete the layer with the given name.
+
+    up [<lower path>[:<lower path>]]
+        mount the given layer with the given lower paths. print the mount path.
+
+    dn
+        unmount the given layer.

lyr.sh

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+#!/bin/sh
+
+set -e
+
+export LYRROOT="$(dirname "$(readlink -f "$0")")"
+export LYRREPO="${LYRREPO:-/usr/var/lyr}"
+
+[ -n "$1" ] || { \
+echo "
+usage: $(basename $0) <command> <layer name>
+
+commands:
+    workdir
+        returns the work directory path for the layer.
+
+    upperdir
+        returns the upper directory path for the layer.
+
+    mountdir
+        returns the mount directory path for the layer.
+
+    mk
+        create a new layer with the given name.
+
+    rm
+        unmount and delete the layer with the given name.
+
+    up [<lower path>[:<lower path>]]
+        mount the given layer with the given lower paths. print the mount path.
+
+    dn
+        unmount the given layer.
+" && exit 0; }
+
+# if this is running on an interactive
+# terminal (as opposed to in a script), if tput is installed, and if tput
+# knows some color codes, then set the color values.
+if [ -t 1 ] && [ "$(tput colors 2>/dev/null || echo 0)" -ge 8 ]; then
+    _clr="$(tput sgr0)"
+    _blu="$(tput setaf 6)"
+    _ylw="$(tput setaf 3)"
+    _red="$(tput setaf 1)"
+fi
+log() { echo "$_blu[LOG]$_clr $@"; }
+wrn() { echo "$_ylw[WRN]$_clr $@" >&2; }
+err() { echo "$_red[ERR]$_clr $@" >&2; exit 1; }
+
+case "$1" in
+    workdir) echo "$LYRREPO/work/$2";;
+    upperdir) echo "$LYRREPO/upper/$2";;
+    mountdir) echo "$LYRREPO/mount/$2";;
+    mk) mkdir -p "$LYRREPO/upper/$2";;
+
+    rm)
+        { ! mountpoint -q "$LYRREPO/mount/$2" || umount "$LYRREPO/mount/$2"; } \
+        && rm -fr "$LYRREPO/upper/$2" "$LYRREPO/mount/$2" "$LYRREPO/work/$2"
+        ;;
+
+    up)
+        [ -n "$3" ] && { layer="$3" && lower="$2"; } || layer="$2"
+        work="$LYRREPO/work/$layer"
+        upper="$LYRREPO/upper/$layer"
+        mnt="$LYRREPO/mount/$layer"
+        [ -d "$upper" ] || err "layer '$layer' not recognized!"
+
+        mkdir -p "$work" "$mnt"
+
+        if [ -n "$lower" ]; then
+            mount -t overlay -o lowerdir=$lower,upperdir=$upper,workdir=$work \
+            none "$mnt"
+        else
+            mount -o bind "$upper" "$mnt"
+        fi
+
+        echo "$mnt"
+        ;;
+
+    dn) umount "$LYRREPO/mount/$2" && rm -r "$LYRREPO/mount/$2";;
+    *) err "unrecognized command '$1'";;
+esac

makefile

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+SRCDIR = $(dir $(realpath $(firstword $(MAKEFILE_LIST))))
+PREFIX ?= /usr
+DESTDIR ?= $(PREFIX)/bin
+LYRREPO ?= $(PREFIX)/var/lyr
+LYRROOT ?= $(PREFIX)/share/lyr
+
+install: 
+	mkdir -p $(LYRREPO)
+	ln -sf $(SRCDIR) $(LYRROOT)
+	ln -sf $(LYRROOT)/lyr.sh $(DESTDIR)/lyr
+
+uninstall:
+	rm $(DESTDIR)/lyr
+	rm $(LYRROOT)
+	rm -fr $(LYRREPO)

sloc.sh

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+#!/bin/sh
+
+# find all *.sh files not under `pkg` that are not symbolic links, strip all
+# trailing whitespace, then all leading whitespace, then all lines starting
+# with '#', then all empty lines. then count the remaining lines.
+
+find . -name "*.sh" ! -path "**/pkg/**" ! -type l \
+| xargs sed 's/[[:space:]]*$//g; s/^[[:space:]]*//g; s/^#.*$//g; /^$/d' \
+| wc -l - \
+| cut -d' ' -f1
+
+# note that this script's ELOC is also included in the count.