cpt: keep the file structure simpler

FossilOrigin-Name: b548c2cdb7abfada1c7527565e5a58b2de5bbb6d620682454828cee7ae15b5db

1 files changed, 1526 insertions, 0 deletions

diff --git a/tools/cpt-lib b/tools/cpt-lib
new file mode 100644
index 0000000..c72f7f9
--- /dev/null
+++ b/tools/cpt-lib
@@ -0,0 +1,1526 @@
+#!/bin/sh -ef
+# shellcheck source=/dev/null
+#
+# This is a simple package manager written in POSIX 'sh' for use
+# in KISS Linux (https://k1ss.org).
+#
+# This script runs with '-ef' meaning:
+# '-e': Abort on any non-zero exit code.
+# '-f': Disable globbing globally.
+#
+# [1] Warnings related to word splitting and globbing are disabled.
+# All word splitting in this script is *safe* and intentional.
+#
+# Dylan Araps.
+
+version() {
+    log "Carbs Packaging Tools" 3.0.0
+    exit 0
+}
+
+out() {
+    # Print a message as is.
+    printf '%s\n' "$@"
+}
+
+log() {
+    # Print a message prettily.
+    #
+    # All messages are printed to stderr to allow the user to hide build
+    # output which is the only thing printed to stdout.
+    #
+    # '\033[1;32m'        Set text to color '2' and make it bold.
+    # '\033[m':           Reset text formatting.
+    # '${3:-->}':         If the 3rd argument is missing, set prefix to '->'.
+    # '${2:+\033[1;3Xm}': If the 2nd argument exists, set text style of '$1'.
+    printf '\033[1;33m%s \033[m%b%s\033[m %s\n' \
+           "${3:-->}" "${2:+"\033[1;36m"}" "$1" "$2" >&2
+}
+
+die() {
+    # Print a message and exit with '1' (error).
+    log "$1" "$2" "!>"
+    exit 1
+}
+
+warn() {
+    # Print a warning message
+    log "WARN" "$1" "${2:-!>}"
+}
+
+contains() {
+    # Check if a "string list" contains a word.
+    case " $1 " in *" $2 "*) return 0; esac; return 1
+}
+
+regesc() {
+    # Escape special regular expression characters as
+    # defined in POSIX BRE. '$.*[\^'
+    printf '%s\n' "$1" | sed 's|\\|\\\\|g;s|\[|\\[|g;s|\$|\\$|g;s|\.|\\.|g;s|\*|\\*|g;s|\^|\\^|g'
+}
+
+
+prompt() {
+    # If a CPT_NOPROMPT variable is set, continue.
+    # This can be useful for installation scripts and
+    # bootstrapping.
+    [ "$CPT_PROMPT" = 0 ] && return 0
+
+    # Ask the user for some input.
+    [ "$1" ] && log "$1"
+    log "Continue?: Press Enter to continue or Ctrl+C to abort here"
+
+    # POSIX 'read' has none of the "nice" options like '-n', '-p'
+    # etc etc. This is the most basic usage of 'read'.
+    # '_' is used as 'dash' errors when no variable is given to 'read'.
+    read -r _ || return 1
+}
+
+as_root() {
+    # Simple function to run a command as root using either 'sudo',
+    # 'doas' or 'su'. Hurrah for choice.
+    [ "$uid" = 0 ] || log "Using '${su:-su}' (to become ${user:=root})"
+
+    case ${su##*/} in
+        sudo) sudo -E -u "$user" -- "$@" ;;
+        doas) doas    -u "$user" -- "$@" ;;
+        su)   su -pc "env USER=$user $* <&3" "$user" 3<&0 </dev/tty ;;
+        *)    die "Invalid CPT_SU value: $su" ;;
+    esac
+}
+
+pop() {
+    # Remove an item from a "string list". This allows us
+    # to remove a 'sed' call and reuse this code throughout.
+    del=$1
+    shift 2
+
+    for i do [ "$i" = "$del" ] || printf %s " $i "; done
+}
+
+run_hook() {
+    # If a fourth parameter 'root' is specified, source
+    # the hook from a predefined location to avoid privilige
+    # escalation through user scripts.
+    [ "$4" ] && CPT_HOOK=$CPT_ROOT/etc/cpt-hook
+
+    # This is not a misspelling, can be ignored safely.
+    # shellcheck disable=2153
+    [ -f "$CPT_HOOK" ] || return 0
+
+    log "$2" "Running $1 hook"
+
+    TYPE=${1:-null} PKG=${2:-null} DEST=${3:-null} . "$CPT_HOOK"
+}
+
+decompress() {
+    case $1 in
+        *.tar)      cat       ;;
+        *.bz2)      bzip2 -cd ;;
+        *.xz|*.txz) xz -dcT 0 ;;
+        *.tgz|*.gz) gzip -cd  ;;
+        *.zst)      zstd -cd  ;;
+    esac < "$1"
+}
+
+sh256() {
+    # This is a sha256sum function for outputting a standard
+    # hash digest. sha256 on BSD systems require an '-r' flag
+    # for outputting the same way with sha256sum, and still,
+    # it outputs a single space between the hash and the file
+    # whereas sha256sum outputs double spaces. It fallbacks to
+    # openssl, but that is rarely ever needed.
+    { sha256sum "$1" 2>/dev/null   ||
+      sha256 -r "$1" 2>/dev/null   ||
+      openssl dgst -r -sha256 "$1" ||
+      die "No sha256 program could be run." ;} |
+
+        while read -r hash _; do printf '%s  %s\n' "$hash" "$1"; done
+}
+
+pkg_isbuilt() (
+    # Check if a package is built or not.
+    repo_dir=$(pkg_find "$1")
+    read -r ver rel < "$repo_dir/version"
+
+    set +f
+    for tarball in "$bin_dir/$1#$ver-$rel.tar."*; do
+        [ -f "$tarball" ] && return 0
+    done
+    return 1
+)
+
+pkg_lint() {
+    # Check that each mandatory file in the package entry exists.
+    log "$1" "Checking repository files"
+
+    repo_dir=$(pkg_find "$1")
+
+    cd "$repo_dir" || die "'$repo_dir' not accessible"
+    [ -f sources ] || die "$1" "Sources file not found"
+    [ -x build ]   || die "$1" "Build file not found or not executable"
+    [ -s version ] || die "$1" "Version file not found or empty"
+
+    read -r _ release 2>/dev/null < version || die "Version file not found"
+    [ "$release" ] || die "Release field not found in version file"
+
+    [ "$2" ] || [ -f checksums ] || die "$pkg" "Checksums are missing"
+}
+
+pkg_find() {
+    # Use a SEARCH_PATH variable so that we can get the sys_db into
+    # the same variable as CPT_PATH. This makes it easier when we are
+    # searching for executables instead of CPT_PATH.
+    : "${SEARCH_PATH:=$CPT_PATH:$sys_db}"
+
+    # Figure out which repository a package belongs to by
+    # searching for directories matching the package name
+    # in $CPT_PATH/*.
+    query=$1 match=$2 type=$3 IFS=:; set --
+
+    # Word splitting is intentional here.
+    # shellcheck disable=2086
+    for path in $SEARCH_PATH ; do
+        set +f
+
+        for path2 in "$path/"$query; do
+            test "${type:--d}" "$path2" && set -f -- "$@" "$path2"
+        done
+    done
+
+    unset IFS
+
+    # A package may also not be found due to a repository not being
+    # readable by the current user. Either way, we need to die here.
+    [ "$1" ] || die "Package '$query' not in any repository"
+
+    # Show all search results if called from 'cpt search', else
+    # print only the first match.
+    [ "$match" ] && printf '%s\n' "$@" || printf '%s\n' "$1"
+}
+
+pkg_list() {
+    # List installed packages. As the format is files and
+    # directories, this just involves a simple for loop and
+    # file read.
+
+    # Change directories to the database. This allows us to
+    # avoid having to 'basename' each path. If this fails,
+    # set '$1' to mimic a failed glob which indicates that
+    # nothing is installed.
+    cd "$sys_db" 2>/dev/null || set -- "$sys_db/"\*
+
+    # Optional arguments can be passed to check for specific
+    # packages. If no arguments are passed, list all. As we
+    # loop over '$@', if there aren't any arguments we can
+    # just set the directory contents to the argument list.
+    [ "$1" ] || { set +f; set -f -- *; }
+
+    # If the 'glob' above failed, exit early as there are no
+    # packages installed.
+    [ "$1" = "$sys_db/"\* ] && return 1
+
+    # Loop over each package and print its name and version.
+    for pkg do
+        [ -d "$pkg" ] || { log "$pkg" "not installed"; return 1; }
+
+        read -r version 2>/dev/null < "$pkg/version" || version=null
+        printf '%s\n' "$pkg $version"
+    done
+}
+
+pkg_cache() {
+    read -r version release 2>/dev/null < "$(pkg_find "$1")/version"
+
+    set +f; set -f -- "$bin_dir/$1#$version-$release.tar."*
+    tar_file=$1
+
+    [ -f "$tar_file" ]
+}
+
+pkg_sources() {
+    # Download any remote package sources. The existence of local
+    # files is also checked.
+    log "$1" "Downloading sources"
+
+    # Store each downloaded source in a directory named after the
+    # package it belongs to. This avoid conflicts between two packages
+    # having a source of the same name.
+    mkdir -p "$src_dir/$1" && cd "$src_dir/$1"
+
+    repo_dir=$(pkg_find "$1")
+
+    while read -r src dest || [ "$src" ]; do
+        # Comment.
+        if [ -z "${src##\#*}" ]; then :
+
+        # Remote source (cached).
+        elif [ -f "${src##*/}" ]; then
+            log "$1" "Found cached source '${src##*/}'"
+
+        # Remote git repository.
+        elif [ -z "${src##git+*}" ]; then
+            # This is a checksums check, skip it.
+            [ "$2" ] && continue
+
+            # Since git is an optional dependency, make sure
+            # it is available on the system.
+            command -v git >/dev/null ||
+                die "git must be installed in order to acquire ${src##git+}"
+
+            mkdir -p "$mak_dir/$1/$dest"
+
+            # Run in a subshell to keep the variables, path and
+            # argument list local to each loop iteration.
+            (
+                repo_src=${src##git+}
+
+                log "$1" "Cloning ${repo_src%[@#]*}"
+
+                # Git has no option to clone a repository to a
+                # specific location so we must do it ourselves
+                # beforehand.
+                cd "$mak_dir/$1/$dest" 2>/dev/null || die
+
+                # Clear the argument list as we'll be overwriting
+                # it below based on what kind of checkout we're
+                # dealing with.
+                set -- "$repo_src"
+
+                # If a branch was given, shallow clone it directly.
+                # This speeds things up as we don't have to grab
+                # a lot of unneeded commits.
+                [ "${src##*@*}" ] ||
+                    set -- -b "${src##*@}" "${repo_src%@*}"
+
+                # Maintain compatibility with older versions of
+                # cpt by shallow cloning all branches. This has
+                # the added benefit of allowing checkouts of
+                # specific commits in specific branches.
+                [ "${src##*#*}" ] ||
+                    set -- --no-single-branch "${repo_src%#*}"
+
+                # Always do a shallow clone as we will unshallow it if
+                # needed later (when a commit is desired).
+                git clone --depth=1 "$@" .
+
+            ) || die "$1" "Failed to clone $src"
+
+        # Remote source.
+        elif [ -z "${src##*://*}" ]; then
+            log "$1" "Downloading $src"
+
+            curl "$src" -fLo "${src##*/}" || {
+                rm -f "${src##*/}"
+                die "$1" "Failed to download $src"
+            }
+
+        # Local source.
+        elif [ -f "$repo_dir/$src" ]; then
+            log "$1" "Found local file '$src'"
+
+        else
+            die "$1" "No local file '$src'"
+        fi
+    done < "$repo_dir/sources"
+}
+
+pkg_extract() {
+    # Extract all source archives to the build directory and copy over
+    # any local repository files.
+    log "$1" "Extracting sources"
+
+    repo_dir=$(pkg_find "$1")
+
+    while read -r src dest || [ "$src" ]; do
+        mkdir -p "$mak_dir/$1/$dest" && cd "$mak_dir/$1/$dest"
+
+        case $src in
+            # Git repository with supplied commit hash.
+            git+*\#*)
+                log "Checking out ${src##*#}"
+
+                # A commit was requested, unshallow the repository.
+                # This will convert it to a regular repository with
+                # full history.
+                git fetch --unshallow
+
+                # Try to checkout the repository. If we fail here,
+                # the requested commit doesn't exist.
+                git -c advice.detachedHead=false checkout "${src##*#}" ||
+                    die "Commit hash ${src##*#} doesn't exist"
+            ;;
+
+            # Git repository, comment or blank line.
+            git+*|\#*|'') continue ;;
+
+            # Only 'tar' an 'zip' archives are currently supported for
+            # extraction. Other filetypes are simply copied to '$mak_dir'
+            # which allows for manual extraction.
+            *://*.tar|*://*.tar.??|*://*.tar.???|*://*.tar.????|*://*.tgz|*://*.txz)
+
+                decompress "$src_dir/$1/${src##*/}" > .ktar
+
+                "$tar" xf .ktar || die "$1" "Couldn't extract ${src##*/}"
+
+                # We now list the contents of the tarball so we can do our
+                # version of 'strip-components'.
+                "$tar" tf .ktar |
+                    while read -r file; do printf '%s\n' "${file%%/*}"; done |
+
+                    # Do not repeat files.
+                    uniq |
+
+                    # For every directory in the base we move each file
+                    # inside it to the upper directory.
+                    while read -r dir ; do
+
+                        # Skip if we are not dealing with a directory here.
+                        # This way we don't remove files on the upper directory
+                        # if a tar archive doesn't need directory stripping.
+                        [ -d "${dir#.}" ] || continue
+
+                        # Change into the directory in a subshell so we don't
+                        # need to cd back to the upper directory.
+                        (
+                            cd "$dir"
+
+                            # We use find because we want to move hidden files
+                            # as well.
+                            #
+                            # Skip the file if it has the same name as the directory.
+                            # We will deal with it later.
+                            #
+                            # Word splitting is intentional here.
+                            # shellcheck disable=2046
+                            find . \( ! -name . -prune \) ! -name "$dir" \
+                                 -exec mv -f {} .. \;
+
+                            # If a file/directory with the same name as the directory
+                            # exists, append a '.cptbak' to it and move it to the
+                            # upper directory.
+                            ! [ -e "$dir" ] || mv "$dir" "../${dir}.cptbak"
+                        )
+                        rmdir "$dir"
+
+                        # If a backup file exists, move it into the original location.
+                        ! [ -e "${dir}.cptbak" ] || mv "${dir}.cptbak" "$dir"
+                done
+
+                # Clean up the temporary tarball.
+                rm -f .ktar
+            ;;
+
+            *://*.zip)
+                unzip "$src_dir/$1/${src##*/}" ||
+                    die "$1" "Couldn't extract ${src##*/}"
+
+            ;;
+
+            *)
+                # Local file.
+                if [ -f "$repo_dir/$src" ]; then
+                    cp -f "$repo_dir/$src" .
+
+                # Remote file.
+                elif [ -f "$src_dir/$1/${src##*/}" ]; then
+                    cp -f "$src_dir/$1/${src##*/}" .
+
+                else
+                    die "$1" "Local file $src not found"
+                fi
+            ;;
+        esac
+    done < "$repo_dir/sources"
+}
+
+pkg_depends() {
+    # Resolve all dependencies and generate an ordered list.
+    # This does a depth-first search. The deepest dependencies are
+    # listed first and then the parents in reverse order.
+    contains "$deps" "$1" || {
+        # Filter out non-explicit, aleady installed dependencies.
+        # Only filter installed if called from 'pkg_build()'.
+        [ "$pkg_build" ] && [ -z "$2" ] &&
+            (pkg_list "$1" >/dev/null) && return
+
+        # Recurse through the dependencies of the child packages.
+        while read -r dep _ || [ "$dep" ]; do
+            [ "${dep##\#*}" ] && pkg_depends "$dep"
+        done 2>/dev/null < "$(pkg_find "$1")/depends" ||:
+
+        # After child dependencies are added to the list,
+        # add the package which depends on them.
+        [ "$2" = explicit ] || deps="$deps $1 "
+    }
+}
+
+pkg_order() {
+    # Order a list of packages based on dependence and
+    # take into account pre-built tarballs if this is
+    # to be called from 'cpt i'.
+    order=; redro=; deps=
+
+    for pkg do case $pkg in
+        *.tar.*) deps="$deps $pkg "  ;;
+        *)       pkg_depends "$pkg" raw
+    esac done
+
+    # Filter the list, only keeping explicit packages.
+    # The purpose of these two loops is to order the
+    # argument list based on dependence.
+    for pkg in $deps; do ! contains "$*" "$pkg" || {
+        order="$order $pkg "
+        redro=" $pkg $redro"
+    } done
+
+    deps=
+}
+
+pkg_strip() {
+    # Strip package binaries and libraries. This saves space on the
+    # system as well as on the tarballs we ship for installation.
+
+    # Package has stripping disabled, stop here.
+    [ -f "$mak_dir/$pkg/nostrip" ] && return
+
+    log "$1" "Stripping binaries and libraries"
+
+    find "$pkg_dir/$1" -type f | while read -r file; do
+        case $(od -A o -t c -N 18 "$file") in
+            # REL (object files (.o), static libraries (.a)).
+            *177*E*L*F*0000020\ 001\ *|*\!*\<*a*r*c*h*\>*)
+                strip -g -R .comment -R .note "$file"
+            ;;
+
+            # EXEC (static binaries).
+            # DYN (shared libraries, dynamic binaries).
+            # Shared libraries keep global symbols in a separate ELF section
+            # called '.dynsym'. '--strip-all/-s' does not touch the dynamic
+            # symbol entries which makes this safe to do.
+            *177*E*L*F*0000020\ 00[23]\ *)
+                strip -s -R .comment -R .note "$file"
+            ;;
+        esac
+    done 2>/dev/null ||:
+}
+
+pkg_fixdeps() {
+    # Dynamically look for missing runtime dependencies by checking
+    # each binary and library with 'ldd'. This catches any extra
+    # libraries and or dependencies pulled in by the package's
+    # build suite.
+    log "$1" "Checking for missing dependencies"
+
+    # Go to the directory containing the built package to
+    # simplify path building.
+    cd "$pkg_dir/$1/$pkg_db/$1"
+
+    # Make a copy of the depends file if it exists to have a
+    # reference to 'diff' against.
+    if [ -f depends ]; then
+        cp -f depends "$mak_dir/d"
+        dep_file=$mak_dir/d
+    else
+        dep_file=/dev/null
+    fi
+
+    # Generate a list of all installed manifests.
+    pkg_name=$1
+    set +f; set -f -- "$sys_db/"*/manifest
+
+    # Get a list of binaries and libraries, false files
+    # will be found, however it's faster to get 'ldd' to check
+    # them anyway than to filter them out.
+    find "$pkg_dir/$pkg_name/" -type f 2>/dev/null |
+
+    while read -r file; do
+        # Run 'ldd' on the file and parse each line. The code
+        # then checks to see which packages own the linked
+        # libraries and it prints the result.
+        ldd "$file" 2>/dev/null | while read -r dep; do
+            # Skip lines containing 'ldd'.
+            [ "${dep##*ldd*}" ] || continue
+
+            # Extract the file path from 'ldd' output, and
+            # canonicalize the path.
+            dep=${dep#* => }
+            dep=${dep% *}
+            dep=$(cpt-readlink "$dep")
+
+            # Figure out which package owns the file.
+            own=$("$grep" -lFx "${dep#$CPT_ROOT}" "$@")
+
+            # If the package wasn't found, retry by removing
+            # the '/usr' prefix.
+            if [ -z "$own" ] && [ -z "${dep##$CPT_ROOT/usr*}" ]; then
+                own=$("$grep" -lFx "${dep#$CPT_ROOT/usr}" "$@")
+                dep=${dep#/usr}
+            fi
+
+            # Extract package name from 'grep' match.
+            own=${own%/*}
+            own=${own##*/}
+
+            case $own in "$pkg_name"|"$pkg_name-bin"|"") continue ; esac
+            printf 'Found %s (%s) in (%s)\n' "$own" "$dep" \
+                   "${file##$pkg_dir/$pkg_name}" >/dev/tty
+
+            printf '%s\n' "$own"
+        done ||:
+    done >> depends
+
+    # Remove duplicate entries from the new depends file.
+    # This removes duplicate lines looking *only* at the
+    # first column.
+    sort -uk1,1 -o depends depends 2>/dev/null ||:
+
+    # Display a diff of the new dependencies against the old ones.
+    diff -U 3 "$dep_file" depends 2>/dev/null ||:
+
+    # Remove the depends file if it is empty.
+    [ -s depends ] || rm -f depends
+}
+
+pkg_manifest() (
+    # Generate the package's manifest file. This is a list of each file
+    # and directory inside the package. The file is used when uninstalling
+    # packages, checking for package conflicts and for general debugging.
+    log "$1" "Generating manifest"
+
+    # This function runs as a sub-shell to avoid having to 'cd' back to the
+    # prior directory before being able to continue.
+    cd "${2:-$pkg_dir}/$1"
+
+    # find: Print all files and directories and append '/' to directories.
+    # sort: Sort the output in *reverse*. Directories appear *after* their
+    #       contents.
+    # sed:  Remove the first character in each line (./dir -> /dir) and
+    #       remove all lines which only contain '.'.
+    find . -type d -exec printf '%s/\n' {} + -o -print |
+        sort -r | sed '/^\.\/$/d;ss.ss' > "${2:-$pkg_dir}/$1/$pkg_db/$1/manifest"
+)
+
+pkg_etcsums() (
+    # This function runs as a sub-shell to avoid having to 'cd' back to the
+    # prior directory before being able to continue.
+    cd "$pkg_dir/$1/etc" 2>/dev/null || return 0; cd ..
+
+    # Generate checksums for each configuration file in the package's
+    # /etc/ directory for use in "smart" handling of these files.
+    log "$1" "Generating etcsums"
+
+
+    find etc -type f | while read -r file; do
+        sh256 "$file"
+    done > "$pkg_dir/$1/$pkg_db/$1/etcsums"
+)
+
+pkg_tar() {
+    # Create a tarball from the built package's files.
+    # This tarball also contains the package's database entry.
+    log "$1" "Creating tarball"
+
+    # Read the version information to name the package.
+    read -r version release < "$(pkg_find "$1")/version"
+
+    # Create a tarball from the contents of the built package.
+    "$tar" cf - -C "$pkg_dir/$1" . |
+        case $CPT_COMPRESS in
+            bz2) bzip2 -z ;;
+            xz)  xz -zT 0 ;;
+            gz)  gzip -6  ;;
+            zst) zstd -3  ;;
+            *)   gzip -6  ;;  # Fallback to gzip
+        esac \
+    > "$bin_dir/$1#$version-$release.tar.$CPT_COMPRESS"
+
+    log "$1" "Successfully created tarball"
+
+    run_hook post-package "$1" "$bin_dir/$1#$version-$release.tar.$CPT_COMPRESS"
+}
+
+pkg_build() {
+    # Build packages and turn them into packaged tarballs. This function
+    # also checks checksums, downloads sources and ensure all dependencies
+    # are installed.
+    pkg_build=1
+
+    log "Resolving dependencies"
+
+    for pkg do contains "$explicit" "$pkg" || {
+        pkg_depends "$pkg" explicit
+
+        # Mark packages passed on the command-line
+        # separately from those detected as dependencies.
+        explicit="$explicit $pkg "
+    } done
+
+    [ "$pkg_update" ] || explicit_build=$explicit
+
+    # If an explicit package is a dependency of another explicit
+    # package, remove it from the explicit list as it needs to be
+    # installed as a dependency.
+    # shellcheck disable=2086
+    for pkg do
+        contains "$deps" "$pkg" && explicit=$(pop "$pkg" from $explicit)
+    done
+
+    # See [1] at top of script.
+    # shellcheck disable=2046,2086
+    set -- $deps $explicit
+
+    log "Building: $*"
+
+    # Only ask for confirmation if more than one package needs to be built.
+    [ $# -gt 1 ] || [ "$pkg_update" ] && { prompt || exit 0 ;}
+
+    log "Checking for pre-built dependencies"
+
+    for pkg do pkg_lint "$pkg"; done
+
+    # Install any pre-built dependencies if they exist in the binary
+    # directory and are up to date.
+    for pkg do ! contains "$explicit_build" "$pkg" && pkg_cache "$pkg" && {
+        log "$pkg" "Found pre-built binary, installing"
+        (CPT_FORCE=1 cpt-install "$tar_file")
+
+        # Remove the now installed package from the build list.
+        # See [1] at top of script.
+        # shellcheck disable=2046,2086
+        set -- $(pop "$pkg" from "$@")
+    } done
+
+    for pkg do pkg_sources "$pkg"; done
+
+    pkg_verify "$@"
+
+    # Finally build and create tarballs for all passed packages and
+    # dependencies.
+    for pkg do
+        log "$pkg" "Building package ($((in = in + 1))/$#)"
+
+        pkg_extract "$pkg"
+        repo_dir=$(pkg_find "$pkg")
+
+        read -r build_version _ < "$repo_dir/version"
+
+        # Install built packages to a directory under the package name
+        # to avoid collisions with other packages.
+        mkdir -p "$pkg_dir/$pkg/$pkg_db"
+
+        # Move to the build directory.
+        cd "$mak_dir/$pkg"
+
+        log "$pkg" "Starting build"
+
+        run_hook pre-build "$pkg" "$pkg_dir/$pkg"
+
+        # Call the build script, log the output to the terminal
+        # and to a file. There's no PIPEFAIL in POSIX shelll so
+        # we must resort to tricks like killing the script ourselves.
+        { "$repo_dir/build" "$pkg_dir/$pkg" "$build_version" "$sys_arch" 2>&1 || {
+            log "$pkg" "Build failed"
+            log "$pkg" "Log stored to $log_dir/$pkg-$time-$pid"
+            run_hook build-fail "$pkg" "$pkg_dir/$pkg"
+            pkg_clean
+            kill 0
+        } } | tee "$log_dir/$pkg-$time-$pid"
+
+        # Delete the log file if the build succeeded to prevent
+        # the directory from filling very quickly with useless logs.
+        [ "$CPT_KEEPLOG" = 1 ] || rm -f "$log_dir/$pkg-$time-$pid"
+
+        # Copy the repository files to the package directory.
+        # This acts as the database entry.
+        cp -LRf "$repo_dir" "$pkg_dir/$pkg/$pkg_db/"
+
+        # We never ever want this. Let's end the endless conflicts
+        # and remove it. This will be the only exception for a
+        # specific removal of this kind.
+        find "$pkg_dir/$pkg" -name charset.alias -exec rm -f {} +
+
+        log "$pkg" "Successfully built package"
+
+        run_hook post-build "$pkg" "$pkg_dir/$pkg"
+
+        # Create the manifest file early and make it empty.
+        # This ensures that the manifest is added to the manifest.
+        : > "$pkg_dir/$pkg/$pkg_db/$pkg/manifest"
+
+        # If the package contains '/etc', add a file called
+        # 'etcsums' to the manifest. See comment directly above.
+        [ -d "$pkg_dir/$pkg/etc" ] &&
+            : > "$pkg_dir/$pkg/$pkg_db/$pkg/etcsums"
+
+        pkg_strip    "$pkg"
+        pkg_fixdeps  "$pkg"
+        pkg_manifest "$pkg"
+        pkg_etcsums  "$pkg"
+        pkg_tar      "$pkg"
+
+        # Install only dependencies of passed packages.
+        # Skip this check if this is a package update.
+        contains "$explicit" "$pkg" && [ -z "$pkg_update" ] && continue
+
+        log "$pkg" "Needed as a dependency or has an update, installing"
+
+        (CPT_FORCE=1 cpt-install "$pkg")
+    done
+
+    # End here as this was a system update and all packages have been installed.
+    [ "$pkg_update" ] && return
+
+    log "Successfully built package(s)"
+
+    # Turn the explicit packages into a 'list'.
+    # See [1] at top of script.
+    # shellcheck disable=2046,2086
+    set -- $explicit
+
+    # Only ask for confirmation if more than one package needs to be installed.
+    [ $# -gt 1 ] && prompt "Install built packages? [$*]" && {
+        cpt-install "$@"
+        return
+    }
+
+    log "Run 'cpt i $*' to install the package(s)"
+}
+
+pkg_checksums() {
+    # Generate checksums for packages.
+    repo_dir=$(pkg_find "$1")
+
+    while read -r src _ || [ "$src" ]; do
+        # Comment.
+        if [ -z "${src##\#*}" ]; then
+            continue
+
+        # File is local to the package.
+        elif [ -f "$repo_dir/$src" ]; then
+            src_path=$repo_dir/${src%/*}
+
+        # File is remote and was downloaded.
+        elif [ -f "$src_dir/$1/${src##*/}" ]; then
+            src_path=$src_dir/$1
+
+        # File is a git repository.
+        elif [ -z "${src##git+*}" ]; then
+            printf 'git  %s\n' "$src"
+            continue
+
+        # Die here if source for some reason, doesn't exist.
+        else
+            die "$1" "Couldn't find source '$src'"
+        fi
+
+        # An easy way to get 'sha256sum' to print with the 'basename'
+        # of files is to 'cd' to the file's directory beforehand.
+        (cd "$src_path" && sh256 "${src##*/}") ||
+            die "$1" "Failed to generate checksums"
+    done < "$repo_dir/sources"
+}
+
+pkg_verify() {
+    # Verify all package checksums. This is achieved by generating
+    # a new set of checksums and then comparing those with the old
+    # set.
+    for pkg do pkg_checksums "$pkg" | diff - "$(pkg_find "$pkg")/checksums" || {
+        log "$pkg" "Checksum mismatch"
+
+        # Instead of dying above, log it to the terminal. Also define a
+        # variable so we *can* die after all checksum files have been
+        # checked.
+        mismatch="$mismatch$pkg "
+    } done
+
+    [ -z "$mismatch" ] || die "Checksum mismatch with: ${mismatch% }"
+}
+
+pkg_conflicts() {
+    # Check to see if a package conflicts with another.
+    log "$1" "Checking for package conflicts"
+
+    # Filter the tarball's manifest and select only files
+    # and any files they resolve to on the filesystem
+    # (/bin/ls -> /usr/bin/ls).
+    while read -r file; do
+        case $file in */) continue; esac
+
+        # Use $CPT_ROOT in filename so that we follow its symlinks.
+        file=$CPT_ROOT/${file#/}
+
+        # We will only follow the symlinks of the directories, so we
+        # reserve the directory name in this 'dirname' value. cpt-readlink
+        # functions in a similar fashion to 'readlink -f', it makes sure
+        # every component except for the first one to be available on
+        # the directory structure. If we cannot find it in the system,
+        # we don't need to make this much more complex by trying so
+        # hard to find it. Simply use the original directory name.
+        dirname="$(cpt-readlink "${file%/*}" 2>/dev/null)" ||
+            dirname="${file%/*}"
+
+
+        # Combine the dirname and file values, and print them into the
+        # temporary manifest to be parsed.
+        printf '%s/%s\n' "${dirname#$CPT_ROOT}" "${file##*/}"
+
+    done < "$tar_dir/$1/$pkg_db/$1/manifest" > "$CPT_TMPDIR/$pid-m"
+
+    p_name=$1
+
+    # Generate a list of all installed package manifests
+    # and remove the current package from the list.
+    # shellcheck disable=2046,2086
+    set -- $(set +f; pop "$sys_db/$p_name/manifest" from "$sys_db"/*/manifest)
+
+    [ -s "$CPT_TMPDIR/$pid-m" ] || return 0
+
+    # In rare cases where the system only has one package installed
+    # and you are reinstalling that package, grep will try to read from
+    # standard input if we continue here.
+    #
+    # Also, if we don't have any packages installed grep will give an
+    # error. This will not cause the installation to fail, but we don't
+    # need to check for conflicts if that's the case anyway. If we have
+    # only zero packages or one package, just stop wasting time and continue
+    # with the installation.
+    [ "$1" ] && [ -f "$1" ] || return 0
+
+    # Store the list of found conflicts in a file as we will be using the
+    # information multiple times. Storing it in the cache dir allows us
+    # to be lazy as they'll be automatically removed on script end.
+    "$grep" -Fxf "$CPT_TMPDIR/$pid-m" -- "$@" > "$CPT_TMPDIR/$pid-c" ||:
+
+
+    # Enable alternatives automatically if it is safe to do so.
+    # This checks to see that the package that is about to be installed
+    # doesn't overwrite anything it shouldn't in '/var/db/cpt/installed'.
+    "$grep" -q ":/var/db/cpt/installed/" "$CPT_TMPDIR/$pid-c" || choice_auto=1
+
+    # Use 'grep' to list matching lines between the to
+    # be installed package's manifest and the above filtered
+    # list.
+    if [ "$CPT_CHOICE" != 0 ] && [ "$choice_auto" = 1 ]; then
+
+        # This is a novel way of offering an "alternatives" system.
+        # It is entirely dynamic and all "choices" are created and
+        # destroyed on the fly.
+        #
+        # When a conflict is found between two packages, the file
+        # is moved to a directory called "choices" and its name
+        # changed to store its parent package and its intended
+        # location.
+        #
+        # The package's manifest is then updated to reflect this
+        # new location.
+        #
+        # The 'cpt choices' command parses this directory and
+        # offers you the CHOICE of *swapping* entries in this
+        # directory for those on the filesystem.
+        #
+        # The choices command does the same thing we do here,
+        # it rewrites manifests and moves files around to make
+        # this work.
+        #
+        # Pretty nifty huh?
+        while IFS=: read -r _ con; do
+            printf '%s\n' "Found conflict $con"
+
+            # Create the "choices" directory inside of the tarball.
+            # This directory will store the conflicting file.
+            mkdir -p "$tar_dir/$p_name/${cho_dir:=var/db/cpt/choices}"
+
+            # Construct the file name of the "db" entry of the
+            # conflicting file. (pkg_name>usr>bin>ls)
+            con_name=$(printf %s "$con" | sed 's|/|>|g')
+
+            # Move the conflicting file to the choices directory
+            # and name it according to the format above.
+            mv -f "$tar_dir/$p_name/$con" \
+                  "$tar_dir/$p_name/$cho_dir/$p_name$con_name" 2>/dev/null || {
+                log "File must be in ${con%/*} and not a symlink to it"
+                log "This usually occurs when a binary is installed to"
+                log "/sbin instead of /usr/bin (example)"
+                log "Before this package can be used as an alternative,"
+                log "this must be fixed in $p_name. Contact the maintainer"
+                die "by checking 'git log' or by running 'cpt-maintainer'"
+            }
+        done < "$CPT_TMPDIR/$pid-c"
+
+        # Rewrite the package's manifest to update its location
+        # to its new spot (and name) in the choices directory.
+        pkg_manifest "$p_name" "$tar_dir" 2>/dev/null
+
+    elif [ -s "$CPT_TMPDIR/$pid-c" ]; then
+        log "Package '$p_name' conflicts with another package" "" "!>"
+        log "Run 'CPT_CHOICE=1 cpt i $p_name' to add conflicts" "" "!>"
+        die "as alternatives."
+    fi
+}
+
+pkg_swap() {
+    # Swap between package alternatives.
+    pkg_list "$1" >/dev/null
+
+    alt=$(printf %s "$1$2" | sed 's|/|>|g')
+    cd "$sys_db/../choices"
+
+    [ -f "$alt" ] || [ -h "$alt" ] ||
+        die "Alternative '$1 $2' doesn't exist"
+
+    if [ -f "$2" ]; then
+        # Figure out which package owns the file we are going to swap for
+        # another package's.
+        #
+        # Print the full path to the manifest file which contains
+        # the match to our search.
+        pkg_owns=$(set +f; "$grep" -lFx "$2" "$sys_db/"*/manifest) ||:
+
+        # Extract the package name from the path above.
+        pkg_owns=${pkg_owns%/*}
+        pkg_owns=${pkg_owns##*/}
+
+        [ "$pkg_owns" ] ||
+            die "File '$2' exists on filesystem but isn't owned"
+
+        log "Swapping '$2' from '$pkg_owns' to '$1'"
+
+        # Convert the current owner to an alternative and rewrite
+        # its manifest file to reflect this. We then resort this file
+        # so no issues arise when removing packages.
+        cp  -Pf "$CPT_ROOT/$2" "$pkg_owns>${alt#*>}"
+        sed "s#^$(regesc "$2")#${PWD#$CPT_ROOT}/$pkg_owns>${alt#*>}#" \
+            "../installed/$pkg_owns/manifest" |
+            sort -r -o "../installed/$pkg_owns/manifest"
+    fi
+
+    # Convert the desired alternative to a real file and rewrite
+    # the manifest file to reflect this. The reverse of above.
+    mv -f "$alt" "$CPT_ROOT/$2"
+    sed "s#^${PWD#$CPT_ROOT}/$(regesc "$alt")#$2#" "../installed/$1/manifest" |
+        sort -r -o "../installed/$1/manifest"
+}
+
+pkg_etc() {
+    [ -d "$tar_dir/$pkg_name/etc" ] || return 0
+
+    (cd "$tar_dir/$pkg_name"
+
+    # Create all directories beforehand.
+    find etc -type d | while read -r dir; do
+        mkdir -p "$CPT_ROOT/$dir"
+    done
+
+    # Handle files in /etc/ based on a 3-way checksum check.
+    find etc ! -type d | while read -r file; do
+        { sum_new=$(sh256 "$file")
+          sum_sys=$(cd "$CPT_ROOT/"; sh256 "$file")
+          sum_old=$("$grep" "$file$" "$mak_dir/c"); } 2>/dev/null ||:
+
+        log "$pkg_name" "Doing 3-way handshake for $file"
+        printf '%s\n' "Previous: ${sum_old:-null}"
+        printf '%s\n' "System:   ${sum_sys:-null}"
+        printf '%s\n' "New:      ${sum_new:-null}"
+
+        # Use a case statement to easily compare three strings at
+        # the same time. Pretty nifty.
+        case ${sum_old:-null}${sum_sys:-null}${sum_new} in
+            # old = Y, sys = X, new = Y
+            "${sum_new}${sum_sys}${sum_old}")
+                log "Skipping $file"
+                continue
+            ;;
+
+            # old = X, sys = X, new = X
+            # old = X, sys = Y, new = Y
+            # old = X, sys = X, new = Y
+            "${sum_old}${sum_old}${sum_old}"|\
+            "${sum_old:-null}${sum_sys}${sum_sys}"|\
+            "${sum_sys}${sum_old}"*)
+                log "Installing $file"
+                new=
+            ;;
+
+            # All other cases.
+            *)
+                warn "($pkg_name) saving /$file as /$file.new" "->"
+                new=.new
+            ;;
+        esac
+
+        cp -fPp "$file"  "$CPT_ROOT/${file}${new}"
+        chown root:root "$CPT_ROOT/${file}${new}" 2>/dev/null
+    done) ||:
+}
+
+pkg_remove() {
+    # Remove a package and all of its files. The '/etc' directory
+    # is handled differently and configuration files are *not*
+    # overwritten.
+    pkg_list "$1" >/dev/null || return
+
+    # Make sure that nothing depends on this package.
+    [ "$CPT_FORCE" = 1 ] || {
+        log "$1" "Checking for reverse dependencies"
+
+        (cd "$sys_db"; set +f; grep -lFx "$1" -- */depends) &&
+            die "$1" "Can't remove package, others depend on it"
+    }
+    # Block being able to abort the script with 'Ctrl+C' during removal.
+    # Removes all risk of the user aborting a package removal leaving
+    # an incomplete package installed.
+    trap '' INT
+
+    if [ -x "$sys_db/$1/pre-remove" ]; then
+        log "$1" "Running pre-remove script"
+        "$sys_db/$1/pre-remove" ||:
+    fi
+
+    # Create a temporary list of all directories, so we don't accidentally
+    # remove anything from packages that create empty directories for a
+    # purpose (such as baselayout).
+    manifest_list="$(set +f; pop "$sys_db/$1/manifest" from "$sys_db/"*/manifest)"
+    # shellcheck disable=2086
+    [ "$manifest_list" ] && grep -h '/$' $manifest_list | sort -ur > "$mak_dir/dirs"
+
+    run_hook pre-remove "$1" "$sys_db/$1" root
+
+    while read -r file; do
+        # The file is in '/etc' skip it. This prevents the package
+        # manager from removing user edited configuration files.
+        [ "${file##/etc/*}" ] || continue
+
+        if [ -d "$CPT_ROOT/$file" ]; then
+            "$grep" -Fxq "$file" "$mak_dir/dirs" 2>/dev/null && continue
+            rmdir "$CPT_ROOT/$file" 2>/dev/null || continue
+        else
+            rm -f "$CPT_ROOT/$file"
+        fi
+    done < "$sys_db/$1/manifest"
+
+    # Reset 'trap' to its original value. Removal is done so
+    # we no longer need to block 'Ctrl+C'.
+    trap pkg_clean EXIT INT
+
+    run_hook post-remove "$1" "$CPT_ROOT/" root
+
+    log "$1" "Removed successfully"
+}
+
+pkg_install() {
+    # Install a built package tarball.
+
+    # Install can also take the full path to a tarball.
+    # We don't need to check the repository if this is the case.
+    if [ -f "$1" ] && [ -z "${1%%*.tar*}" ] ; then
+        tar_file=$1
+        pkg_name=${1##*/}
+        pkg_name=${pkg_name%#*}
+
+    else
+        pkg_cache "$1" ||
+            die "package has not been built, run 'cpt b pkg'"
+
+        pkg_name=$1
+    fi
+
+    mkdir -p "$tar_dir/$pkg_name"
+    log "$pkg_name" "Extracting $tar_file"
+
+    # Extract the tarball to catch any errors before installation begins.
+    decompress "$tar_file" | "$tar" xf - -C "$tar_dir/$pkg_name"
+
+    [ -f "$tar_dir/$pkg_name/$pkg_db/$pkg_name/manifest" ] ||
+        die "'${tar_file##*/}' is not a valid CPT package"
+
+    # Ensure that the tarball's manifest is correct by checking that
+    # each file and directory inside of it actually exists.
+    [ "$CPT_FORCE" != 1 ] && log "$pkg_name" "Checking package manifest" &&
+        while read -r line; do
+            # Skip symbolic links
+            [ -h "$tar_dir/$pkg_name/$line" ] ||
+            [ -e "$tar_dir/$pkg_name/$line" ] || {
+        log "File $line missing from tarball but mentioned in manifest" "" "!>"
+        TARBALL_FAIL=1
+        }
+    done < "$tar_dir/$pkg_name/$pkg_db/$pkg_name/manifest"
+    [ "$TARBALL_FAIL" ] && {
+        log "You can still install this package by setting CPT_FORCE variable"
+        die "$pkg_name" "Missing files in manifest"
+    }
+
+    log "$pkg_name" "Checking that all dependencies are installed"
+
+    # Make sure that all run-time dependencies are installed prior to
+    # installing the package.
+    [ -f "$tar_dir/$pkg_name/$pkg_db/$pkg_name/depends" ] &&
+    [ "$CPT_FORCE" != 1 ] &&
+        while read -r dep dep_type || [ "$dep" ]; do
+            [ "${dep##\#*}" ] || continue
+            [ "$dep_type" ]   || pkg_list "$dep" >/dev/null ||
+                install_dep="$install_dep'$dep', "
+        done < "$tar_dir/$pkg_name/$pkg_db/$pkg_name/depends"
+
+    [ "$install_dep" ] && die "$1" "Package requires ${install_dep%, }"
+
+    run_hook pre-install "$pkg_name" "$tar_dir/$pkg_name" root
+
+    pkg_conflicts "$pkg_name"
+
+    log "$pkg_name" "Installing package incrementally"
+
+    # Block being able to abort the script with Ctrl+C during installation.
+    # Removes all risk of the user aborting a package installation leaving
+    # an incomplete package installed.
+    trap '' INT
+
+    # If the package is already installed (and this is an upgrade) make a
+    # backup of the manifest and etcsums files.
+    cp -f "$sys_db/$pkg_name/manifest" "$mak_dir/m" 2>/dev/null ||:
+    cp -f "$sys_db/$pkg_name/etcsums"  "$mak_dir/c" 2>/dev/null ||:
+
+    # This is repeated multiple times. Better to make it a function.
+    pkg_rsync() {
+        rsync "--chown=$USER:$USER" --chmod=Du-s,Dg-s,Do-s \
+              -WhHKa --no-compress --exclude /etc "${1:---}" \
+              "$tar_dir/$pkg_name/" "$CPT_ROOT/"
+    }
+
+    # Install the package by using 'rsync' and overwrite any existing files
+    # (excluding '/etc/').
+    pkg_rsync --info=progress2
+    pkg_etc
+
+    # Remove any leftover files if this is an upgrade.
+    "$grep" -vFxf "$sys_db/$pkg_name/manifest" "$mak_dir/m" 2>/dev/null |
+
+    while read -r file; do
+        file=$CPT_ROOT/$file
+
+        # Skip deleting some leftover files.
+        case $file in /etc/*) continue; esac
+
+        # Remove files.
+        if [ -f "$file" ] && [ ! -L "$file" ]; then
+            rm -f "$file"
+
+        # Remove file symlinks.
+        elif [ -h "$file" ] && [ ! -d "$file" ]; then
+            unlink "$file" ||:
+
+        # Skip directory symlinks.
+        elif [ -h "$file" ] && [ -d "$file" ]; then :
+
+        # Remove directories if empty.
+        elif [ -d "$file" ]; then
+            rmdir "$file" 2>/dev/null ||:
+        fi
+    done ||:
+
+    log "$pkg_name" "Verifying installation"
+    { pkg_rsync; pkg_rsync; } ||:
+
+    # Reset 'trap' to its original value. Installation is done so
+    # we no longer need to block 'Ctrl+C'.
+    trap pkg_clean EXIT INT
+
+    if [ -x "$sys_db/$pkg_name/post-install" ]; then
+        log "$pkg_name" "Running post-install script"
+        "$sys_db/$pkg_name/post-install" ||:
+    fi
+
+    run_hook post-install "$pkg_name" "$sys_db/$pkg_name" root
+
+    log "$pkg_name" "Installed successfully"
+}
+
+pkg_fetch() {
+    log "Updating repositories"
+
+    run_hook pre-fetch
+
+    # Create a list of all repositories.
+    # See [1] at top of script.
+    # shellcheck disable=2046,2086
+    { IFS=:; set -- $CPT_PATH; unset IFS; }
+
+    # Update each repository in '$CPT_PATH'. It is assumed that
+    # each repository is 'git' tracked.
+    for repo do
+        # Go to the root of the repository (if it exists).
+        cd "$repo"
+        cd "$(git rev-parse --show-toplevel 2>/dev/null)" 2>/dev/null ||:
+
+        if [ -d .git ]; then
+
+            command -v git >/dev/null || {
+                log "$repo" " "
+                printf '%s\n' "Git is not installed, skipping."
+                continue
+            }
+
+            [ "$(git remote 2>/dev/null)" ] || {
+                log "$repo" " "
+                printf '%s\n' "No remote, skipping."
+                continue
+            }
+
+            contains "$repos" "$PWD" || {
+                repos="$repos $PWD "
+
+                # Display a tick if signing is enabled for this
+                # repository.
+                case $(git config merge.verifySignatures) in
+                    true) log "$PWD" "[signed ✓] " ;;
+                    *)    log "$PWD" " " ;;
+                esac
+
+                if [ -w "$PWD" ] && [ "$uid" != 0 ]; then
+                    git fetch
+                    git merge
+                    git submodule update --remote --init -f
+
+                else
+                    [ "$uid" = 0 ] || log "$PWD" "Need root to update"
+
+                    # Find out the owner of the repository and spawn
+                    # git as this user below.
+                    #
+                    # This prevents 'git' from changing the original
+                    # ownership of files and directories in the rare
+                    # case that the repository is owned by a 3rd user.
+                    (
+                        user=$(cpt-stat "$PWD")      || user=root
+                        id -u "$user" >/dev/null 2>&1 || user=root
+
+                        [ "$user" = root ] ||
+                            log "Dropping permissions to $user for pull"
+
+                        git_cmd="git fetch && git merge && git submodule update --remote --init -f"
+                        case $su in *su) git_cmd="'$git_cmd'"; esac
+
+                        # Spawn a subshell to run multiple commands as
+                        # root at once. This makes things easier on users
+                        # who aren't using persist/timestamps for auth
+                        # caching.
+                        user=$user as_root sh -c "$git_cmd"
+                    )
+                fi
+            }
+        elif [ -f .rsync ]; then
+            read -r remote < .rsync
+            if [ -w "$PWD" ] && [ "$uid" != 0 ]; then
+                rsync -acvzzC --include=core --delete "$remote/" "$PWD"
+            else
+                [ "$uid" = 0 ] || log "$PWD" "Need root to update"
+
+                # Similar to the git update, we find the owner of
+                # the repository and spawn rsync as that user.
+                (
+                    user=$(cpt-stat "$PWD")      || user=root
+                    id -u "$user" >/dev/null 2>&1 || user=root
+
+                    [ "$user" = root ] ||
+                        log "Dropping permissions to $user for pull"
+
+                    user=$user as_root rsync -acvzzC --include=core --delete "$remote/" "$PWD"
+                )
+            fi
+        else
+            log "$repo" " "
+            printf '%s\n' "Not a remote repository, skipping."
+        fi
+    done
+
+    run_hook post-fetch
+}
+
+pkg_updates(){
+    # Check all installed packages for updates. So long as the installed
+    # version and the version in the repositories differ, it's considered
+    # an update.
+    [ "$CPT_FETCH" = 0 ] || pkg_fetch
+
+    log "Checking for new package versions"
+
+    set +f
+
+    for pkg in "$sys_db/"*; do
+        pkg_name=${pkg##*/}
+
+        # Read version and release information from the installed packages
+        # and repository.
+        read -r db_ver db_rel < "$pkg/version"
+        read -r re_ver re_rel < "$(pkg_find "$pkg_name")/version"
+
+        # Compare installed packages to repository packages.
+        [ "$db_ver-$db_rel" != "$re_ver-$re_rel" ] && {
+            printf '%s\n' "$pkg_name $db_ver-$db_rel ==> $re_ver-$re_rel"
+            outdated="$outdated$pkg_name "
+        }
+    done
+
+    set -f
+
+    # If the download option is specified only download the outdated packages
+    # and exit.
+    [ "$download_only" = 1 ] && {
+        log "Only sources for the packages will be acquired"
+        prompt || exit 0
+
+        for pkg in $outdated; do
+            pkg_sources "$pkg"
+        done
+
+        exit 0
+    }
+
+    contains "$outdated" cpt && {
+        log "Detected package manager update"
+        log "The package manager will be updated first"
+
+        prompt || exit 0
+
+        pkg_build cpt
+        cpt-install cpt
+
+        log "Updated the package manager"
+        log "Re-run 'cpt update' to update your system"
+
+        exit 0
+    }
+
+    [ "$outdated" ] || {
+        log "Everything is up to date"
+        return
+    }
+
+    log "Packages to update: ${outdated% }"
+
+    # Tell 'pkg_build' to always prompt before build.
+    pkg_update=1
+
+    # Build all packages requiring an update.
+    # See [1] at top of script.
+    # shellcheck disable=2046,2086
+    {
+        pkg_order $outdated
+        pkg_build $order
+    }
+
+    log "Updated all packages"
+}
+
+pkg_clean() {
+    # Clean up on exit or error. This removes everything related
+    # to the build.
+    [ "$CPT_DEBUG" != 1 ] || return
+
+    # Block 'Ctrl+C' while cache is being cleaned.
+    trap '' INT
+
+    # Remove temporary items.
+    rm -rf -- "$mak_dir" "$pkg_dir" "$tar_dir" \
+       "$CPT_TMPDIR/$pid-c" "$CPT_TMPDIR/$pid-m"
+}
+
+main() {
+    set -ef
+
+    # Die here if the user has no set CPT_PATH. This is a rare occurance
+    # as the environment variable should always be defined.
+    [ "$CPT_PATH" ] || die "\$CPT_PATH needs to be set"
+
+    # Set the location to the repository and package database.
+    pkg_db=var/db/cpt/installed
+
+    # The PID of the current shell process is used to isolate directories
+    # to each specific CPT instance. This allows multiple package manager
+    # instances to be run at once. Store the value in another variable so
+    # that it doesn't change beneath us.
+    pid=${CPT_PID:-$$}
+
+    # Force the C locale to speed up things like 'grep' which disable unicode
+    # etc when this is set. We don't need unicode and a speed up is always
+    # welcome.
+    export LC_ALL=C LANG=C
+
+    # Catch errors and ensure that build files and directories are cleaned
+    # up before we die. This occurs on 'Ctrl+C' as well as success and error.
+    trap pkg_clean EXIT INT
+
+    # Prefer GNU grep if installed as it is much much faster than busybox's
+    # implementation. Very much worth it if you value performance over
+    # POSIX correctness (grep quoted to avoid shellcheck false-positive).
+    grep=$(command -v ggrep) || grep='grep'
+
+    # Prefer libarchive tar or GNU tar if installed as they are  much
+    # much faster than busybox's implementation. Very much worth it if
+    # you value performance.
+    tar=$(command -v bsdtar || command -v gtar) || tar=tar
+
+    # Figure out which 'sudo' command to use based on the user's choice or
+    # what is available on the system.
+    su=${CPT_SU:-$(command -v sudo || command -v doas)} || su=su
+
+    # Store the date and time of script invocation to be used as the name
+    # of the log files the package manager creates uring builds.
+    time=$(date '+%Y-%m-%d-%H:%M')
+
+    # Make note of the user's current ID to do root checks later on.
+    # This is used enough to warrant a place here.
+    uid=$(id -u)
+
+    # Make sure that the CPT_ROOT doesn't end with a '/'. This might
+    # break some operations.
+    [ -z "$CPT_ROOT" ] || [ "${CPT_ROOT##*/}" ] || {
+        warn "Your CPT_ROOT variable shouldn't end with '/'"
+        CPT_ROOT=${CPT_ROOT%/}
+    }
+
+    # Define an optional sys_arch variable in order to provide
+    # information to build files with architectural information.
+    sys_arch=$(uname -m 2>/dev/null) ||:
+
+    # Define this variable but don't create its directory structure from
+    # the get go. It will be created as needed by package installation.
+    sys_db=$CPT_ROOT/$pkg_db
+
+    # This allows for automatic setup of a CPT chroot and will
+    # do nothing on a normal system.
+    mkdir -p "$CPT_ROOT/" 2>/dev/null ||:
+
+    # Set a value for CPT_COMPRESS if it isn't set.
+    : "${CPT_COMPRESS:=gz}"
+
+    # A temporary directory can be specified apart from the cache
+    # directory in order to build in a user specified directory.
+    # /tmp could be used in order to build on ram, useful on SSDs.
+    # The user can specify CPT_TMPDIR for this.
+    #
+    # Create the required temporary directories and set the variables
+    # which point to them.
+    mkdir -p "${cac_dir:=${CPT_CACHE:=${XDG_CACHE_HOME:-$HOME/.cache}/cpt}}" \
+             "${CPT_TMPDIR:=$cac_dir}" \
+             "${mak_dir:=$CPT_TMPDIR/build-$pid}" \
+             "${pkg_dir:=$CPT_TMPDIR/pkg-$pid}" \
+             "${tar_dir:=$CPT_TMPDIR/extract-$pid}" \
+             "${src_dir:=$cac_dir/sources}" \
+             "${log_dir:=$cac_dir/logs}" \
+             "${bin_dir:=$cac_dir/bin}"
+
+    # Disable color escape sequences if running in a subshell.
+    # This behaviour can be changed by adding a CPT_COLOR
+    # variable to the environment. If it is set to 1 it will
+    # always enable color escapes, and if set to 0 it will
+    # always disable color escapes.
+    if [ "$CPT_COLOR" = 1 ]; then color=1
+    elif [ "$CPT_COLOR" = 0 ] || ! [ -t 1 ]; then
+        log() { printf '%s %s %s\n' "${3:-->}" "$1" "$2" >&2 ;}
+    else color=1
+    fi
+
+}
+
+main "$@"