On Sun, 2018-08-12 at 10:36 +0200, [email protected] wrote: > On Sun, Aug 12, 2018 at 01:26:40AM -0400, Jim Popovitch wrote: > > On Sun, 2018-08-12 at 00:48 +0200, [email protected] wrote: > > > On Sat, Aug 11, 2018 at 06:08:34PM -0400, Jim Popovitch wrote: > > > > Hello! > > > > > > > > What's the best way to grab anything that's in stdin into a > > > > variable > > > > inside a bash script, but won't block if stdin is null? > > > > > > I think read is your friend (at least in bash). It has an option > > > -t <timeout>, which you can set to zero, for it to just grab > > > what's > > > available at the moment without waiting (cf "help read" while in > > > the bash for more details, like setting a delimiter, etc.) > > > > > > HTH > > > -- tomás > > > > Thanks for the reply tomás. I'm trying to avoid using read because > > of > > the 1 sec minimum timeout. > > Not on bash, at least. According to the docs, "-t 0" is a timeout of > zero. Experiments confirm that: > > tomas@trotzki:~$ time read -t 0 > > real 0m0.000s > user 0m0.000s > sys 0m0.000s > > (Of course, 0 is too optimistic here, but it's sub-millisecond). > Fractional times work too: > > tomas@trotzki:~$ time read -t 0.05 > > real 0m0.050s > user 0m0.000s > sys 0m0.000s > > Finally, you can use timeout to read incomplete (i.e. non-terminated) > input, like so: > > tomas@trotzki:~$ time echo -n mumble | bash -c 'read -t 0.01 foo ; > echo $foo' > mumble > > real 0m0.004s > user 0m0.000s > sys 0m0.000s > > Note that "-t 0" won't work here: the "read" at the right is there > before > the "echo" at the left, so read turns out empty... > > > This may seem odd, but 1 sec is 100+ > > times > > longer than grep'ing/awk'ing/sed'ing the contents of a variable, so > > I'm > > trying to find a faster way to read stdin. > > No, it doesn't seem odd. Sometimes 1 sec is too much (sometimes 1msec > is > too much, too :-) > > But I think (used wisely) read is still your friend! > > Note that I didn't check how much of this is bashism. Document your > requirements :-)
:-) Turns out I had mis-read your first reply as "-t 1", chiefly because that was all that I had found before posting here. What now works for me avoids the -t param: while read stdin_line do MSG=$MSG"\n"$stdin_line done < /dev/stdin Thanks again, -Jim P.
