function __fish_umask_parse -d "Internal umask function"
    # Test if already a valid octal mask, and pad it with zeros
    if echo $argv | __fish_sgrep -E '^0?[0-7]{1,3}$' >/dev/null
        set -l char_count (echo $argv| wc -c)
        for i in (seq (math 5 - $char_count))
            set argv 0$argv
        end
        echo $argv
    else
        # Test if argument really is a valid symbolic mask
        if not echo $argv | __fish_sgrep -E '^(((u|g|o|a|)(=|\+|-)|)(r|w|x)*)(,(((u|g|o|a|)(=|\+|-)|)(r|w|x)*))*$' >/dev/null
            printf (_ "%s: Invalid mask '%s'\n") umask $argv >&2
            return 1
        end

        set -l implicit_all

        # Insert inverted umask into res variable

        set -l mode
        set -l val
        set -l tmp $umask
        set -l res

        for i in 1 2 3
            set tmp (echo $tmp|cut -c 2-)
            set -l char_count (echo $tmp|cut -c 1)
            set res[$i] (math 7 - $char_count)
        end

        set -l el (echo $argv|tr , \n)
        for i in $el
            switch $i
                case 'u*'
                    set idx 1
                    set i (echo $i| cut -c 2-)

                case 'g*'
                    set idx 2
                    set i (echo $i| cut -c 2-)

                case 'o*'
                    set idx 3
                    set i (echo $i| cut -c 2-)

                case 'a*'
                    set idx 1 2 3
                    set i (echo $i| cut -c 2-)

                case '*'
                    set implicit_all 1
                    set idx 1 2 3
            end

            switch $i
                case '=*'
                    set mode set
                    set i (echo $i| cut -c 2-)

                case '+*'
                    set mode add
                    set i (echo $i| cut -c 2-)

                case '-*'
                    set mode remove
                    set i (echo $i| cut -c 2-)

                case '*'
                    if not count $implicit_all >/dev/null
                        printf (_ "%s: Invalid mask '%s'\n") umask $argv >&2
                        return
                    end
                    set mode set
            end

            if not echo $perm | __fish_sgrep -E '^(r|w|x)*$' >/dev/null
                printf (_ "%s: Invalid mask '%s'\n") umask $argv >&2
                return
            end

            set val 0
            if echo $i | __fish_sgrep 'r' >/dev/null
                set val 4
            end
            if echo $i | __fish_sgrep 'w' >/dev/null
                set val (math $val + 2)
            end
            if echo $i | __fish_sgrep 'x' >/dev/null
                set val (math $val + 1)
            end

            for j in $idx
                switch $mode
                    case set
                        set res[$j] $val

                    case add
                        set res[$j] (perl -e 'print( ( '$res[$j]'|'$val[$j]' )."\n" )')

                    case remove
                        set res[$j] (perl -e 'print( ( (7-'$res[$j]')&'$val[$j]' )."\n" )')
                end
            end
        end

        for i in 1 2 3
            set res[$i] (math 7 - $res[$i])
        end
        echo 0$res[1]$res[2]$res[3]
    end
end

function __fish_umask_print_symbolic
    set -l res ""
    set -l letter a u g o

    for i in 2 3 4
        set res $res,$letter[$i]=
        set val (echo $umask|cut -c $i)

        if contains $val 0 1 2 3
            set res {$res}r
        end

        if contains $val 0 1 4 5
            set res {$res}w
        end

        if contains $val 0 2 4 6
            set res {$res}x
        end

    end

    echo $res | cut -c 2-
end

function umask --description "Set default file permission mask"

    set -l as_command 0
    set -l symbolic 0

    set -l options
    set -l shortopt pSh
    if not getopt -T >/dev/null
        # GNU getopt
        set longopt -l as-command,symbolic,help
        set options -o $shortopt $longopt --
        # Verify options
        if not getopt -n umask $options $argv >/dev/null
            return 1
        end
    else
        # Old getopt, used on OS X
        set options $shortopt
        # Verify options
        if not getopt $options $argv >/dev/null
            return 1
        end
    end

    set -l tmp (getopt $options $argv)
    eval set opt $tmp

    while count $opt >/dev/null

        switch $opt[1]
            case -h --help
                __fish_print_help umask
                return 0

            case -p --as-command
                set as_command 1

            case -S --symbolic
                set symbolic 1

            case --
                set -e opt[1]
                break

        end

        set -e opt[1]

    end

    switch (count $opt)

        case 0
            if not set -q umask
                set -g umask 113
            end
            if test $as_command -eq 1
                echo umask $umask
            else
                if test $symbolic -eq 1
                    __fish_umask_print_symbolic $umask
                else
                    echo $umask
                end
            end

        case 1
            set -l parsed (__fish_umask_parse $opt)
            if test (count $parsed) -eq 1
                set -g umask $parsed
                return 0
            end
            return 1

        case '*'
            printf (_ '%s: Too many arguments\n') umask >&2

    end

end