Re: Bash: command output to variable

Steffen Schuler wrote:
------------------------- (top.pl) ---------------------------------
#!/usr/bin/env perl

# more optimal but less portable as first line:
#!/usr/bin/perl

# to quit the command you have to enter 'q' or 'Q'

# some pragmas to help error finding
use strict;
use warnings;
use diagnostics;


# perlvar: '-no_match_vars' is recommended for performance reasons
use English '-no_match_vars';

use POSIX 'strftime';

# should be installed from CPAN
use Term::ReadKey;

my $logfile = "toplog";
$English::OUTPUT_AUTOFLUSH = 1;
my $clear_string = `clear`;

open(TTY, "</dev/tty");
ReadMode "normal";

open(LOG, ">$logfile") or
die "can't open \"$logfile\": $!";

while (1) {
my $first_line = "\n";
print $clear_string;
if (open(PSOUT,
"ps -eao pcpu,pmem,comm --no-headers --sort=-pcpu |")) {
for (my $i = 0; $i < 10; ++$i) {
if (defined($_ = <PSOUT>)) {
print;
my ($F) = split;
print LOG strftime( '%T', localtime ), " $_" if $F >= 10.0;
}
}
} else {
die "can't open pipe from command: $!";
}

my $key = readKeyQuit(5);
if (defined($key) and $key =~ /q/i) {
exit 0;
}
}

close(PSOUT) or die "cant't close piped command: $!";
close(LOG) or die "can't close \"$logfile\": $!";
close(TTY) or die "can't close \"/dev/tty\": $!";


# reads key with a timeout of 5 seconds without echo
sub readKeyQuit
{
my $timeout = shift;
my $key = '';
eval {
# start alarm handler after $timeout seconds
local $SIG{ALRM} = sub { die "alarm clock restart" };
alarm $timeout;

ReadMode "raw";

# ReadKey 5, *TTY; doesn't seem to work
$key = ReadKey 0, *TTY;

ReadMode "normal";

# start alarm handler immediately
alarm 0;
};

# if the Perl syntax error message string exists and is not
# "alarm clock restart" then die
if ($EVAL_ERROR and $EVAL_ERROR !~ /alarm clock restart/) { die };

return $key;
}
---------------------- end(top.pl) -------------------------------

I didn't recognized that I exited without closing.
Better:

--------------------- begin(top.pl) ---------------------------
#!/usr/bin/env perl

# more optimal but less portable as first line:
#!/usr/bin/perl

# to quit the command you have to enter 'q' or 'Q'

# some pragmas to help error finding
use strict;
use warnings;
use diagnostics;


# perlvar: '-no_match_vars' is recommended for performance reasons
use English '-no_match_vars';

use POSIX 'strftime';

# should be installed from CPAN
use Term::ReadKey;

my $logfile = "toplog";
$English::OUTPUT_AUTOFLUSH = 1;
my $clear_string = `clear`;

open(TTY, "</dev/tty");
ReadMode "normal";

open(LOG, ">$logfile") or
die "can't open \"$logfile\": $!";

my $key;

do {
my $first_line = "\n";
print $clear_string;
if (open(PSOUT,
"ps -eao pcpu,pmem,comm --no-headers --sort=-pcpu |")) {
for (my $i = 0; $i < 10; ++$i) {
if (defined($_ = <PSOUT>)) {
print;
my ($F) = split;
print LOG strftime( '%T', localtime ), " $_" if $F >= 10.0;
}
}
} else {
die "can't open pipe from command: $!";
}

$key = readKeyQuit(5);

} until (defined($key) and $key =~ /q/i);

close(PSOUT) or die "cant't close piped command: $!";
close(LOG) or die "can't close \"$logfile\": $!";
close(TTY) or die "can't close \"/dev/tty\": $!";


# reads key with a timeout of 5 seconds without echo
sub readKeyQuit
{
my $timeout = shift;
my $key = '';
eval {
# start alarm handler after $timeout seconds
local $SIG{ALRM} = sub { die "alarm clock restart" };
alarm $timeout;

ReadMode "raw";

# ReadKey 5, *TTY; doesn't seem to work
$key = ReadKey 0, *TTY;

ReadMode "normal";

# start alarm handler immediately
alarm 0;
};

# if the Perl syntax error message string exists and is not
# "alarm clock restart" then die
if ($EVAL_ERROR and $EVAL_ERROR !~ /alarm clock restart/) { die };

return $key;
}
--------------------- end(top.pl) -----------------------------

Greetings from Munich,

Steffen
.

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