I know that time will send timing statistics output to stderr. But somehow I couldn't capture it either in a bash script or into a file via redirection:
time $cmd 1>/dev/null 2>file
$output=`cat file`
Or
$output=`time $cmd 1>/dev/null`
I'm only interested in timing, not the direct output of the command. I've read some posts overhere but still no luck finding a viable solution. Any suggestions?
Thanks!
Try:
(time $cmd) 1>/dev/null 2>file
so that (time $cmd) is executed in a subshell environment and you can then redirect its output.
(time $cmd 2>/dev/null 1>&2) 2>captured so that stderr from the command gets thrown away, too.(Using GNU time /usr/bin/time rather than bash builtin) (Thanks @Michael Krelin)
(Or invoke as \time) (Thanks @Sorpigal, if I ever knew this I'd entirely forgotten)
How about using the -o and maybe -a command line options:
-o FILE, --output=FILE
Do not send the results to stderr, but overwrite the specified file.
-a, --append
(Used together with -o.) Do not overwrite but append.
"time" quoted to make it use executable and not bash builtin.\time to invoke the executable version.I had a similar issue where I wanted to bench optimizations. The idea was to run the program several times then output statistics on run durations.
I used the following command lines:
1st run: (time ./myprog)2>times.log
Next runs: (time ./myprog)2>>times.log
Note that my (bash?) built-in time outputs statistics in the form:
real 0m2.548s
user 0m7.341s
sys 0m0.007s
Then I ran the following Perl script to retrieve statistics:
#!/usr/bin/perl -w
open FH, './times.log' or die "ERROR: ", $!;
my $useracc1 = 0;
my $useracc2 = 0;
my $usermean = 0;
my $uservar = 0;
my $temp = 0;
while(<FH>)
{
if("$_" =~ /user/)
{
if("$_" =~ /(\d+)m(\d{1,2})\.(\d{3})s/)
{
$usercpt++;
$temp = $1*60 + $2 + $3*0.001;
$useracc1 += $temp;
$useracc2 += $temp**2;
}
}
}
if($usercpt ne 0)
{
$usermean = $useracc1 / $usercpt;
$userdev = sqrt($useracc2 / $usercpt - $usermean**2);
$usermean = int($usermean*1000)/1000;
$userdev = int($userdev*1000)/1000;
}
else
{
$usermean = "---";
$userdev = "---";
}
print "User: ", $usercpt, " runs, avg. ", $usermean, "s, std.dev. ", $userdev,"s\n";
Of course, regular expressions may require adjustements depending on your time output format. It can also be easily extended to include real and system statistics.
