Get the output of time(1) in bash
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Get the output of time(1) in bash
I am using a bash to compile c++ and Java programs.
I need to use the data that time adds, "real", "User", "Sys".
Even though I used var=$( compile ) to get output it shows nothing.
Is there a way to get as a varialbe the outout data of time?
Edited:
I am running the bash on Java with a Proccess and reading the InputStream with a BufferReader.
And closely related (asks about redirection to file, but underlying problem is the same): stackoverflow.com/questions/13356628/…
– Benjamin W.
Aug 7 at 19:27
and BashFAQ/032
– Benjamin W.
Aug 7 at 19:28
2 Answers
2
You can get the full output time echo "hi", and save this to a variable:
time echo "hi"
stats=$( time echo "hi"; 2>&1)
or to a file:
time echo "hi"; >mylogfile.txt 2>&1
The brace syntax here lets bash know what actual information you want. Because time is a reserved word in bash (like if or while), as well as a built-in, redirecting stdout or stderr without braces will not redirect the output from time. To do that, we need to group all the output from the command together, and then redirect it.
if
while
stdout
stderr
time
However, if you only want the timing info, we can redirect the command's information to the void /dev/null and keep only time's output. We can save this to a variable:
/dev/null
time
stats=$( time echo "hi" 1>/dev/null 2>&1; 2>&1)
or to a file:
time echo "hi" 1>/dev/null 2>&1; 2>mylogfile.txt
time is, at least in Bash, more likely a built-in, so man time isn't authoritative, as it refers the binary at /usr/bin/time or wherever it is installed; help time or the Bash man page would have to be consulted.– Benjamin W.
Aug 7 at 19:58
time
man time
/usr/bin/time
help time
(Which has on effect on the solution of redirecting stderr.)
– Benjamin W.
Aug 7 at 19:59
help time is super unhelpful imo. man time at least points out that the output is in stderr, even if it shouldn't be taken as gospel.– jeremysprofile
Aug 7 at 20:01
help time
man time
Helpful or not,
man time talks about something most likely not being executed when you do time <command>. It's not shipped with Bash. man bash has more information under SHELL GRAMMAR / Pipelines, but still doesn't mention that output goes to stderr. It could be argued that writing to stderr is simply POSIX conformant and also intuitively makes sense, as otherwise the output from time would pollute a pipeline that's being measured.– Benjamin W.
Aug 7 at 20:10
man time
time <command>
man bash
time
Time output goes to the error output, so you can use getErrorStream in the process, and then you will get the output from time.
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Cross-site dupe: serverfault.com/questions/175376/…
– Benjamin W.
Aug 7 at 19:26