как установить clang в качестве компилятора по умолчанию вместо gcc в debian

Это может быть лучше с помощью скрипта, который может показывать оставшееся время при отключении с помощью сигнала QUIT (обычно control + \ ) или INFO .

#!/usr/bin/env perl
#
# snooze - sleep for a given duration, with SIGINFO or SIGQUIT
# (control+\ typically) showing how much time remains. Usage:
#
#   snooze 3m; make-noise-somehow
#
# or with
#
#   snooze 25m bread; make-noise-somehow
#
# one can then elsewhere
#
#   pkill -INFO snooze-bread

use strict;
use warnings;
use Term::ReadKey qw(ReadMode);

my %factors = ( s => 1, m => 60, h => 3600, d => 86400 );

my $arg = shift or die "Usage: $0 sleep-time [label]\n";
my $to_sleep = 0;
while ( $arg =~ m/([0-9]+)([smhd])?/g ) {
    my $value  = $1;
    my $factor = $2;
    $value *= $factors{$factor} if $factor;
    $to_sleep += $value;
}
die "nothing to die to sleep to sleep no more for\n" if $to_sleep == 0;

my $label = shift;
$0 = $label ? "snooze-$label" : "snooze";

ReadMode 2;    # noecho to hide control+\s from gunking up the message

sub remainder { warn "$0: " . deltatimefmt($to_sleep) . " remaining\n" }

sub restore {
    ReadMode 0;
    warn "$0: " . deltatimefmt($to_sleep) . " remainds\n";
    exit 1;
}

# expect user to mash on control+\ or whatever generates SIGINFO
for my $name (qw/ALRM INFO QUIT/) {
    $SIG{$name} = \&remainder;
}

# back to original term settings if get blown away
for my $name (qw/HUP INT TERM USR1 USR2/) {
    $SIG{$name} = \&restore;
}

$SIG{TSTP} = 'IGNORE';    # no Zees for you!

while ( $to_sleep > 0 ) {
    $to_sleep -= sleep $to_sleep;
}

ReadMode 0;
exit;

sub deltatimefmt {
    my $difference = shift;

    return "0s" if $difference == 0;

    my $seconds = $difference % 60;
    $difference = ( $difference - $seconds ) / 60;
    my $minutes = $difference % 60;
    $difference = ( $difference - $minutes ) / 60;

    #  my $hours = $difference;
    my $hours = $difference % 24;
    $difference = ( $difference - $hours ) / 24;
    my $days  = $difference % 7;
    my $weeks = ( $difference - $days ) / 7;

    # better way to do this?
    my $temp = ($weeks) ? "${weeks}w " : q{};
    $temp .= ($days)    ? "${days}d "    : q{};
    $temp .= ($hours)   ? "${hours}h "   : q{};
    $temp .= ($minutes) ? "${minutes}m " : q{};
    $temp .= ($seconds) ? "${seconds}s"  : q{};
    return $temp;
}