epm-sh-functions

#!/bin/sh
#
# Copyright (C) 2012, 2014  Etersoft
# Copyright (C) 2012, 2014  Vitaly Lipatov <lav@etersoft.ru>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU Affero General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU Affero General Public License for more details.
#
# You should have received a copy of the GNU Affero General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#

# copied from /etc/init.d/outformat (ALT Linux)


# FIXME on Android: FIX ME! implement ttyname_r() bionic/libc/bionic/stubs.c:366
inputisatty()
{
    # check stdin
    #tty -s 2>/dev/null
    test -t 0
}

isatty()
{
    # check stdout
    test -t 1
}

isatty2()
{
    # check stderr
    test -t 2
}

check_tty()
{
    isatty2 || return

    # Set a sane TERM required for tput
    [ -n "$TERM" ] || TERM=dumb
    export TERM

    check_core_commands

    # grep -E from busybox may not --color
    # grep -E from MacOS print help to stderr
    if grep -E --help 2>&1 | grep -q -- "--color" ; then
        export EGREPCOLOR="--color"
    fi

    is_command tput || return
    # FreeBSD does not support tput -S
    echo | a= tput -S >/dev/null 2>/dev/null || return
    USETTY="tput -S"
}

: ${BLACK:=0} ${RED:=1} ${GREEN:=2} ${YELLOW:=3} ${BLUE:=4} ${MAGENTA:=5} ${CYAN:=6} ${WHITE:=7}

set_boldcolor()
{
    [ -n "$USETTY" ] || return
    {
        echo bold
        echo setaf $1
    } | $USETTY
}

set_color()
{
    [ -n "$USETTY" ] || return
    {
        echo setaf $1
    } | $USETTY
}

restore_color()
{
    [ -n "$USETTY" ] || return
    {
        echo op; # set Original color Pair.
        echo sgr0; # turn off all special graphics mode (bold in our case).
    } | $USETTY
}

echover()
{
    [ -z "$verbose" ] && return
    echo "$*" >&2
}

# echo string without EOL
echon()
{
    # default /bin/sh on MacOS does not recognize -n
    echo -n "$*" 2>/dev/null || a= /bin/echo -n "$*"
}


# Print command line and run command line
showcmd()
{
    if [ -z "$quiet" ] ; then
        set_boldcolor $GREEN
        local PROMTSIG="\$"
        is_root && PROMTSIG="#"
        echo " $PROMTSIG $*"
        restore_color
    fi >&2
}

# Print command
echocmd()
{
    set_boldcolor $GREEN
    local PROMTSIG="\$"
    is_root && PROMTSIG="#"
    echo -n "$PROMTSIG $*"
    restore_color
}

# Print command line and run command line
docmd()
{
    showcmd "$*$EXTRA_SHOWDOCMD"
    "$@"
}

# Run every arg with docmd
docmd_foreach()
{
    local cmd pkg
    cmd="$1"
    #showcmd "$@"
    shift
    for pkg in "$@" ; do
        docmd $cmd $pkg
    done
}

# run command line with SUDO
sudorun()
{
    set_sudo
    if [ -z "$SUDO" ] ; then
        "$@"
        return
    fi
    $SUDO "$@"
}

# Print command line and run command line with SUDO
sudocmd()
{
    set_sudo
    [ -n "$SUDO" ] && showcmd "$SUDO $*" || showcmd "$*"
    sudorun "$@"
}

# Run every arg with sudocmd
# Returns on any error
sudocmd_foreach()
{
    local cmd pkg
    cmd="$1"
    #showcmd "$@"
    shift
    for pkg in "$@" ; do
        # don't quote $cmd here: it can be a command with an args
        sudocmd $cmd $pkg || return
    done
}

# print full path to files
make_filepath()
{
    local i
    for i in "$@" ; do
        [ -f "$i" ] || continue
        echo "$i" | grep -q "/" && echo "$i" && continue
        echo "./$i"
    done
}

get_firstarg()
{
    echon "$1"
}

get_lastarg()
{
    local lastarg
    eval "lastarg=\${$#}"
    echon "$lastarg"
}

# TODO: see etersoft-build-utils/tests/test_isnumber.sh
isnumber()
{
    echo "$*" | filter_strip_spaces | grep -q "^[0-9]\+$"
}

# copied from strings
# CHECKME: the same like estrlist has ?
# Note: used grep -E! write '[0-9]+(first|two)', not '[0-9]\+...'
rhas()
{
    echo "$1" | grep -E -q -- "$2"
}

# bash specific
startwith()
{
    # rhas "$1" "^$2"
    [[ "$1" = ${2}* ]]
}

is_abs_path()
{
    #echo "$1" | grep -q "^/"
    startwith "$1" "/"
}

# copied from strings
is_dirpath()
{
    [ "$1" = "." ] && return $?
    # rhas "$1" "/"
    startwith "$1" "/"
}


filter_strip_spaces()
{
        # possible use just
        #xargs echo
        sed -e "s| \+| |g" | \
                sed -e "s|^ ||" | sed -e "s| \$||"
}

strip_spaces()
{
        echo "$*" | filter_strip_spaces
}


# https://superuser.com/questions/422459/substitution-in-text-file-without-regular-expressions
# http://stackoverflow.com/a/2705678/120999
# use for subst complex string with symbols treating as regexp
sed_escape()
{
    echo "$*" | sed -e 's/[]()$*.^|[]/\\&/g'
}


# param true false
subst_option()
{
    eval "[ -n \"\$$1\" ]" && echo "$2" || echo "$3"
}

store_output()
{
    # use make_temp_file from etersoft-build-utils
    RC_STDOUT="$(mktemp)" || fatal
    remove_on_exit $RC_STDOUT
    local CMDSTATUS=$RC_STDOUT.pipestatus
    echo 1 >$CMDSTATUS
    #RC_STDERR=$(mktemp)
    ( LC_ALL=C $@ 2>&1 ; echo $? >$CMDSTATUS ) | tee $RC_STDOUT
    return "$(cat $CMDSTATUS)"
    # bashism
    # http://tldp.org/LDP/abs/html/bashver3.html#PIPEFAILREF
    #return $PIPESTATUS
}

showcmd_store_output()
{
    showcmd "$@"
    store_output "$@"
}

clean_store_output()
{
    rm -f $RC_STDOUT $RC_STDOUT.pipestatus
}

# run epm, possible from side repo
epm()
{
    if [ "$EPMMODE" = "pipe" ] ; then
        epm_main --inscript "$@"
        return
    fi

    # run epm again to full initialization
    local bashopt=''
    [ -n "$debug" ] && bashopt='-x'

    $CMDSHELL $bashopt $PROGDIR/$PROGNAME --inscript "$@"
}

# run $SUDO epm, possible from side repo
sudoepm()
{
    [ "$EPMMODE" = "pipe" ] && fatal "Can't use sudo epm call from the piped script"

    local bashopt=''
    [ -n "$debug" ] && bashopt='-x'

    sudorun $CMDSHELL $bashopt $PROGDIR/$PROGNAME --inscript "$@"
}

# Print error message and stop the program
fatal()
{
    if [ -z "$TEXTDOMAIN" ] ; then
        set_color $RED >&2
        echo -n "ERROR: " >&2
        restore_color >&2
        echo "$*  (you can discuss the epm $EPMVERSION problem in Telegram: https://t.me/useepm)" >&2
#    else
#        echog "Error in $0: $@" >&2
    fi
#    [ "$TERM" = "screen" ] && echo "(screen detected: waiting ten seconds to exit ...)" >&2 && sleep 10
    exit 1
}

# Print debug message
debug()
{
    [ -n "$debug" ] || return
    if [ -z "$TEXTDOMAIN" ] ; then
        set_color $YELLOW >&2
        echo -n "WARNING: " >&2
        restore_color >&2
        echo "$*" >&2
#    else
#        echog "Error in $0: $@" >&2
    fi
}


# Print warning message
warning()
{
    if [ -z "$TEXTDOMAIN" ] ; then
        set_color $YELLOW >&2
        echo -n "WARNING: " >&2
        restore_color >&2
        echo "$*" >&2
#    else
#        echog "Error in $0: $@" >&2
    fi
}

info()
{
    [ -n "$quiet" ] && return

    # print message to stderr if stderr forwarded to (a file)
    if isatty2 ; then
        isatty || return 0
        echo "$*"
    else
        echo "$*" >&2
    fi
}


check_su_root()
{
    [ "$BASEDISTRNAME" = "alt" ] || return 0

    is_root || return 0

    echo "$PATH" | grep -q "/usr/sbin" && return 0

    fatal "There is missed /usr/sbin path in PATH. Probably you have used 'su' without '-' to get root access. Use 'esu' or 'su -' command to get root permissions."
}


# if we have not sudo, returns 1 and set SUDO variable to fatal
SUDO_TESTED=''
SUDO_CMD='sudo'
set_sudo()
{
    local nofail="$1"

    # cache the result
    [ -n "$SUDO_TESTED" ] && return "$SUDO_TESTED"
    SUDO_TESTED="0"

    SUDO=""
    # skip SUDO if disabled
    [ -n "$EPMNOSUDO" ] && return
    if [ "$DISTRNAME" = "Cygwin" ] || [ "$DISTRNAME" = "Windows" ] ; then
        # skip sudo using on Windows
        return
    fi

    check_su_root

    # if we are root, do not need sudo
    is_root && return

    # start error section
    SUDO_TESTED="1"

    if ! is_command $SUDO_CMD ; then
        [ "$nofail" = "nofail" ] || SUDO="fatal 'For this operation run epm under root, or install and tune sudo (http://altlinux.org/sudo)'"
        SUDO_TESTED="2"
        return "$SUDO_TESTED"
    fi

    # if input is a console
    if inputisatty && isatty && isatty2 ; then
        if ! $SUDO_CMD -n true ; then
            info "Please enter sudo user password to use sudo in the current session."
            if ! $SUDO_CMD -l >/dev/null ; then
                [ "$nofail" = "nofail" ] || SUDO="fatal 'For this operation run epm under root, or install and tune sudo (http://altlinux.org/sudo)'"
                SUDO_TESTED="3"
                return "$SUDO_TESTED"
            fi
        fi
    else
        # use sudo if one is tuned and tuned without password
        if ! $SUDO_CMD -l -n >/dev/null 2>/dev/null ; then
            [ "$nofail" = "nofail" ] || SUDO="fatal 'Can't use sudo (only passwordless sudo is supported here). Please run epm under root or check http://altlinux.org/sudo '"
            SUDO_TESTED="4"
            return "$SUDO_TESTED"
        fi
    fi

    SUDO_TESTED="0"
    # FIXME: does not work: sudo -- VARIABLE=some command
    SUDO="$SUDO_CMD"
    #SUDO="$SUDO_CMD --"
    # check for < 1.7 version which do not support -- (and --help possible too)
    #$SUDO_CMD -h 2>/dev/null | grep -q "  --" || SUDO="$SUDO_CMD"

}

# return TRUE if we can run privileged command
sudo_allowed()
{
    set_sudo nofail
}

# wait for n seconds (if possible) during executing command
# args: seconds command
withtimeout()
{
    local TO=$(print_command_path timeout || print_command_path gtimeout)
    if [ -x "$TO" ] ; then
        $TO "$@"
        return
    fi
    fatal "Possible indefinite wait due timeout command is missed"
    # fallback: drop time arg and run without timeout
    #shift
    #"$@"
}

set_eatmydata()
{
    # don't use eatmydata (useless)
    return 0
    # skip if disabled
    [ -n "$EPMNOEATMYDATA" ] && return
    # use if possible
    is_command eatmydata || return
    set_sudo
    # FIXME: check if SUDO already has eatmydata
    [ -n "$SUDO" ] && SUDO="$SUDO eatmydata" || SUDO="eatmydata"
    [ -n "$verbose" ] && info "Uwaga! eatmydata is installed, we will use it for disable all sync operations."
    return 0
}

# 
__get_package_for_command()
{
    case "$1" in
        equery|revdep-rebuild)
            echo 'gentoolkit'
            ;;
        update-kernel|remove-old-kernels)
            echo 'update-kernel'
            ;;
    esac
}

# TODO:
confirm() {
    local response
    # call with a prompt string or use a default
    read -r -p "${1:-Are you sure? [y/N]} " response
    case $response in
        [yY][eE][sS]|[yY])
            true
            ;;
        *)
            false
            ;;
    esac
}


confirm_info()
{
    info "$*"
    if [ -z "$non_interactive" ] ; then
        confirm "Are you sure? [y/N]" || fatal "Exiting"
    fi

}


is_root()
{
    local EFFUID="$(id -u)"
    [ "$EFFUID" = "0" ]
}

assure_root()
{
    is_root || fatal "run me only under root"
}

check_su_access()
{
    is_command su && return
    [ ! -f /bin/su ] && warning "/bin/su is missed. Try install su package (http://altlinux.org/su)." && return 1
    local group="$(stat -c '%G' /bin/su)" || fatal
    warning "Check if you are in $group group to have access to su command."
    return 1
}

check_sudo_access()
{
    is_command sudo && return
    local cmd=''
    local i
    for i in /bin/sudo /usr/bin/sudo ; do
        [ -f $i ] && cmd="$i"
    done
    [ ! -f $cmd ] && warning "sudo command is missed. Try install sudo package (http://altlinux.org/sudo)." && return 1
    local group="$(stat -c '%G' $cmd)" || fatal
    warning "Check if you are in $group group to have access to sudo command."
    return 1
}

check_sudo_access_only()
{
    is_command sudo && return
    local cmd=''
    local i
    for i in /bin/sudo /usr/bin/sudo ; do
        [ -f $i ] && cmd="$i"
    done
    [ ! -f $cmd ] && return 1
    local group="$(stat -c '%G' $cmd)" || fatal
    warning "sudo command is presence, but is not accessible for you. Check if you are in $group group to have access to sudo command."
    return 1
}

esu()
{
    if is_root ; then
        if [ -n "$*" ] ; then
            [ -n "$quiet" ] || showcmd "$*"
            exec "$@"
        else
            # just shell
            showcmd "su -"
            a= exec su -
        fi
    fi

    set_pm_type


# TODO:
#quote() {
#    for arg in "$@"; do
#        printf '%s\n' "$arg" | sed "s/'/'\\\\''/g;1s/^/'/;\$s/\$/'/"
#    done
#}

    escape_args()
    {
        local output=''
        while [ -n "$1" ] ; do
            if has_space "$1" ; then
                [ -n "$output" ] && output="$output '$1'" || output="'$1'"
            else
                [ -n "$output" ] && output="$output $1" || output="$1"
            fi
            shift
        done
        echo "$output"
    }

    escaped="$(escape_args "$@")"

    check_sudo_access_only
    # sudo is not accessible, will ask root password
    if ! set_sudo ; then
        check_su_access
        #info "Enter root password:"
        if [ -n "$*" ] ; then
            [ -n "$quiet" ] || showcmd "su - -c $escaped"
            a= exec su - -c "$escaped"
        else
            # just shell
            showcmd "su -"
            a= exec su -
        fi
    fi

    check_sudo_access

    #info "You can be asked about your password:"
    if [ -n "$*" ] ; then
        [ -n "$quiet" ] || showcmd "$SUDO su - -c $escaped"
        $SUDO su - -c "$escaped"
    else
        showcmd "$SUDO su -"
        $SUDO su -
    fi
}

regexp_subst()
{
    local expression="$1"
    shift
    sed -i -r -e "$expression" "$@"
}

# TODO: we we can't use epm directly?
assure_exists()
{
    load_helper epm-assure
    local package="$2"
    [ -n "$package" ] || package="$(__get_package_for_command "$1")"

    # ask for install: https://bugzilla.altlinux.org/42240
    local ask=''
    [ -n "$non_interactive" ] || ask=1

    ( verbose='' direct='' interactive=$ask epm_assure "$1" $package $3 ) || fatal
}

assure_exists_erc()
{
    load_helper epm-assure
    local package="erc"
    ( direct='' epm_assure "$package" ) || epm ei erc || fatal "erc is not available to install."
}

# will replaced within disabled_eget in packaged version
eget()
{
    # use internal eget only if exists
    if [ -s $SHAREDIR/tools_eget ] ; then
        ( EGET_BACKEND=$eget_backend $CMDSHELL $SHAREDIR/tools_eget "$@" )
        return
    fi
    fatal "Internal error: missed tools_eget"

    local EGET
    # FIXME: we need disable output here, eget can be used for get output
    assure_exists eget eget 3.3 >/dev/null
    # run external command, not the function
    EGET=$(print_command_path eget) || fatal "Missed command eget from installed package eget"
    $EGET "$@"
}


__epm_assure_7zip()
{
    # install 7zip in any case (can be used)
    if is_command 7z || is_command 7za || is_command 7zr || is_command 7zz ; then
        :
    else
        epm install p7zip
    fi
}

# will replaced within disabled_erc in packaged version
erc()
{

    __epm_assure_7zip

    # use internal eget only if exists
    if [ -s $SHAREDIR/tools_erc ] ; then
        $CMDSHELL $SHAREDIR/tools_erc "$@"
        return
    fi
    fatal "Internal error: missed tools_erc"

    # FIXME: we need disable output here, ercat can be used for get output
    assure_exists_erc >/dev/null
    # run external command, not the function
    local ERC
    ERC=$(print_command_path erc) || fatal "Missed command erc from installed package erc"
    $ERC "$@"
}

# will replaced within disabled_ercat in packaged version
ercat()
{
    local ERCAT
    # use internal eget only if exists
    if [ -s $SHAREDIR/tools_ercat ] ; then
        $CMDSHELL $SHAREDIR/tools_ercat "$@"
        return
    fi
    fatal "Internal error: missed tools_ercat"

    # FIXME: we need disable output here, ercat can be used for get output
    assure_exists_erc >/dev/null
    # run external command, not the function
    ERCAT=$(print_command_path ercat) || fatal "Missed command ercat from installed package erc"
    $ERCAT "$@"
}

estrlist()
{
    if [ -s $SHAREDIR/tools_estrlist ] ; then
        $CMDSHELL $SHAREDIR/tools_estrlist "$@"
        return
    fi
    fatal "missed tools_estrlist"
}

onefile_estrlist()
{
    internal_tools_estrlist "$@"
}

# will replaced within eget() in packed version
onefile_eget()
{
    # check for both
    # we really need that cross here,
    is_command curl || assure_exists wget
    is_command wget || assure_exists curl
    internal_tools_eget "$@"
}

# TODO: improve and drop!
get_package_type()
{
    local i
    case $1 in
        *.deb)
            echo "deb"
            return
            ;;
        *.rpm)
            echo "rpm"
            return
            ;;
        *.txz)
            echo "txz"
            return
            ;;
        *.tbz)
            echo "tbz"
            return
            ;;
        *.exe)
            echo "exe"
            return
            ;;
        *.msi)
            echo "msi"
            return
            ;;
        *.AppImage)
            echo "AppImage"
            return
            ;;
        *)
            if [ -r "$1" ] && file "$1" | grep -q " ELF " ; then
                echo "ELF"
                return
            fi
            # print extension by default
            echo "$1" | sed -e 's|.*\.||'
            return 1
            ;;
    esac
}


# print options description from HELPCMD/HELPOPT lines in the code
# args: section_name, [file with code]
get_help()
{
    if [ "$0" = "/dev/stdin" ] || [ "$0" = "sh" ] ; then
        return
    fi
    local F="$0"
    if [ -n "$2" ] ; then
        is_dirpath "$2" && F="$2" || F="$(dirname $0)/$2"
    fi

    cat "$F" | grep -- "# $1" | while read -r n ; do
        if echo "$n" | grep -q "# $1: PART: " ; then
            echo
            echo "$n" | sed -e "s|# $1: PART: ||"
            continue
        fi
        echo "$n" | grep -q "^ *#" && continue
        opt=`echo $n | sed -e "s|) # $1:.*||g" -e 's|"||g' -e 's@^|@@'`
        desc=`echo $n | sed -e "s|.*) # $1:||g"`
        printf "    %-20s %s\n" "$opt" "$desc"
    done
}

set_bigtmpdir()
{
    # TODO: improve BIGTMPDIR conception
    # https://bugzilla.mozilla.org/show_bug.cgi?id=69938
    # https://refspecs.linuxfoundation.org/FHS_3.0/fhs/ch05s15.html
    # https://geekpeach.net/ru/%D0%BA%D0%B0%D0%BA-systemd-tmpfiles-%D0%BE%D1%87%D0%B8%D1%89%D0%B0%D0%B5%D1%82-tmp-%D0%B8%D0%BB%D0%B8-var-tmp-%D0%B7%D0%B0%D0%BC%D0%B5%D0%BD%D0%B0-tmpwatch-%D0%B2-centos-rhel-7
    [ -z "$BIGTMPDIR" ] && [ -d "/var/tmp" ] && BIGTMPDIR="/var/tmp" || BIGTMPDIR="$TMPDIR"
    export BIGTMPDIR
}

assure_tmpdir()
{
    if [ -z "$TMPDIR" ] ; then
        export TMPDIR="/tmp"
        debug "Your have no TMPDIR defined. Using $TMPDIR as fallback."
    fi

    if [ ! -d "$TMPDIR" ] ; then
        fatal "TMPDIR $TMPDIR does not exist."
    fi

    if [ ! -w "$TMPDIR" ] ; then
        fatal "TMPDIR $TMPDIR is not writable."
    fi
}

set_distro_info()
{
    assure_tmpdir

    set_bigtmpdir

    # don't run again in subprocesses
    [ -n "$DISTRVENDOR" ] && return 0

    DISTRVENDOR=$PROGDIR/distr_info

    # export pack of variables, see epm print info --print-eepm-env
    [ -n "$verbose" ] && $DISTRVENDOR --print-eepm-env
    eval $($DISTRVENDOR --print-eepm-env | grep -v '^ *#')
}

# FIXME: detect if not recognized
set_pm_type()
{
    local CMD
    set_distro_info

# override package manager detection result
if [ -n "$EPM_BACKEND" ] ; then
    PMTYPE=$EPM_BACKEND
    return
fi
# obsoleted
if [ -n "$FORCEPM" ] ; then
    PMTYPE=$FORCEPM
    return
fi

}

is_active_systemd()
{
    [ "$DISTRCONTROL" = "systemd" ]
}

assure_distr()
{
    local TEXT="this option"
    [ -n "$2" ] && TEXT="$2"
    [ "$DISTRNAME" = "$1" ] || fatal "$TEXT supported only for $1 distro"
}

# return delimiter sign in depend of package type
get_pkg_name_delimiter()
{
   local pkgtype="$1"
   [ -n "$pkgtype" ] || pkgtype="$PKGFORMAT"

   [ "$pkgtype" = "deb" ] && echo "_" && return
   echo "-"
}

# used via remove_on_exit
__epm_remove_tmp_files()
{
    trap "-" EXIT
    [ -n "$DEBUG" ] && return 0

    [ -n "$verbose" ] && info "Removing tmp files on exit ..."

    if [ -n "$to_clean_tmp_dirs" ] ; then
        echo "$to_clean_tmp_dirs" | while read p ; do
            [ -n "$verbose" ] && echo "rm -rf '$p'"
            rm -rf "$p" 2>/dev/null
        done
    fi

    if [ -n "$to_clean_tmp_files" ] ; then
        echo "$to_clean_tmp_files" | while read p ; do
            rm $verbose -f "$p" 2>/dev/null
        done
    fi

    return 0
}


remove_on_exit()
{
    if [ -z "$set_remove_on_exit" ] ; then
        trap "__epm_remove_tmp_files" EXIT
        set_remove_on_exit=1
    fi
    while [ -n "$1" ] ; do
        if [ -d "$1" ] ; then
            to_clean_tmp_dirs="$to_clean_tmp_dirs
$1"
        elif [ -f "$1" ] ; then
            to_clean_tmp_files="$to_clean_tmp_files
$1"
        fi
        shift
    done
}

#has_space()
#{
#    estrlist -- has_space "$@"
#}
# use internal implementation for speed
has_space()
{
        # not for dash:
        [ "$1" != "${1/ //}" ]
        # [ "$(echo "$*" | sed -e "s| ||")" != "$*" ]
}


is_url()
{
    echo "$1" | grep -q "^[filehtps]*:/"
}

# print a path to the command if exists in $PATH
if a= type -a type 2>/dev/null >/dev/null ; then
print_command_path()
{
    a= type -fpP -- "$1" 2>/dev/null
}
elif a= which which 2>/dev/null >/dev/null ; then
    # the best case if we have which command (other ways needs checking)
    # TODO: don't use which at all, it is a binary, not builtin shell command
print_command_path()
{
    a= which -- "$1" 2>/dev/null
}
else
print_command_path()
{
    a= type "$1" 2>/dev/null | sed -e 's|.* /|/|'
}
fi

# check if <arg> is a real command
is_command()
{
    print_command_path "$1" >/dev/null
}

# compatibility layer

# add realpath if missed (with -s support)
if ! is_command realpath ; then
realpath()
{
    [ -n "$*" ] || return
    if [ "$1" = "-s" ] ; then
        shift
        echo "$(cd "$(dirname "$1")" && pwd -P)/$(basename "$1")" #"
        return
    fi
    readlink -f "$@"
}
fi


# TODO: use perl if sed -i is not accessible
# sed -i is only supported in GNU sed.
#  sed -i "s/$find/$replace/g" "$@"
#  perl -p -i -e "s/$find/$replace/g" "$@"

# add subst if missed
if ! is_command subst ; then
subst()
{
    sed -i -e "$@"
}
fi

check_core_commands()
{
    #which which >/dev/null || fatal "Can't find which command (which or debianutils package is missed?)"
    is_command grep || fatal "Can't find grep command (coreutils package is missed?)"
    is_command sed || fatal "Can't find sed command (sed package is missed?)"
}