-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 On Sun, Aug 12, 2018 at 01:26:40AM -0400, Jim Popovitch wrote: > On Sun, 2018-08-12 at 00:48 +0200, to...@tuxteam.de 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 :-) Cheers - -- t -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iEYEARECAAYFAltv8XkACgkQBcgs9XrR2kZNaQCcCaWfnVktQY8CENggRODJ3/nl +1UAnRbm/rs66wz+BplEsBX3Mmp3Ed7X =NFpA -----END PGP SIGNATURE-----
