4 ms·

For the author's stated purpose, it sounds like this would work well. However, curl can take a long time to timeout of whatever, depending on server state. I'm

For the author's stated purpose, it sounds like this would work well. However, curl can take a long time to timeout of whatever, depending on server state. I'm curious how people would approach a guaranteeing a maximum time to response or error.

chii 1y ago
In the case of curl, there is a timeout parameter for requests and connections etc. It's what i'd use for checking for a server being up. But in the general case, where the command being invoked does not have such an option, then it does make a lot of sense to do a check like that via the `timeout` utility.
- diggan 1y ago
  For curl: --connect-timeout = Times out if the connection wasn't established within N seconds --max-time = Times out if the entire request wasn't completed within N seconds But then I don't remember if connect-timeout takes DNS lookups into account, or TLS handshakes. I seem to remember there is another sort of timeout that tends to be hard to get right when the connections are flaky/drops a lot of packets, so you end up having to wrap curl anyways if you want a hard limit on the timeout.
  - SoftTalker 1y ago
    I've had many, many cases of processes in Linux getting wedged up bad enough that they cannot be killed. Usually this seems to involve them waiting on I/O.
    - chgs 1y ago
      Kill -9 won’t help in those cases though
cb321 1y ago
It's not POSIX, but both bash & zsh have real time queries built-in (of course, $(date) is an even older school substitute): t1=$((EPOCHSECONDS + 60)) while [ $EPOCHSECONDS -lt $t1 ] do # curl ... && break # or whatnot done There is also EPOCHREALTIME which gives you a floating point to micro or nanoseconds (for bash/zsh), but only Zsh provides FP arithmetic. There are string-manipulation workarounds, of course. And, yes, with Zsh you might need a `zmodload zsh/datetime` in there. These variables seem "under known". EDIT: For example, you can get a quickie wall time measurement from a Zsh shell function like this: dt () { t0=$EPOCHREALTIME "$@" printf "%.7f wallSec\n" "$((EPOCHREALTIME-t0))" >&2 } And then you can actually run in your shell dt echo hi, moon without even a single fork/clone. (which you can confirm with an off to the side `strace -fv -o/dev/shm/dt.st -p WHATEVER_PID`, although I guess the culture these days is often to have even prompt printing launch a zoo of activity)
- michaelcampbell 1y ago
  > These variables seem "under known". I speak only for me but TIL these; thanks!

chii 1y ago

In the case of curl, there is a timeout parameter for requests and connections etc. It's what i'd use for checking for a server being up. But in the general case, where the command being invoked does not have such an option, then it does make a lot of sense to do a check like that via the `timeout` utility.

diggan 1y ago
For curl: --connect-timeout = Times out if the connection wasn't established within N seconds --max-time = Times out if the entire request wasn't completed within N seconds But then I don't remember if connect-timeout takes DNS lookups into account, or TLS handshakes. I seem to remember there is another sort of timeout that tends to be hard to get right when the connections are flaky/drops a lot of packets, so you end up having to wrap curl anyways if you want a hard limit on the timeout.
- SoftTalker 1y ago
  I've had many, many cases of processes in Linux getting wedged up bad enough that they cannot be killed. Usually this seems to involve them waiting on I/O.
  - chgs 1y ago
    Kill -9 won’t help in those cases though

cb321 1y ago

It's not POSIX, but both bash & zsh have real time queries built-in (of course, $(date) is an even older school substitute): t1=$((EPOCHSECONDS + 60)) while [ $EPOCHSECONDS -lt $t1 ] do # curl ... && break # or whatnot done There is also EPOCHREALTIME which gives you a floating point to micro or nanoseconds (for bash/zsh), but only Zsh provides FP arithmetic. There are string-manipulation workarounds, of course. And, yes, with Zsh you might need a `zmodload zsh/datetime` in there. These variables seem "under known". EDIT: For example, you can get a quickie wall time measurement from a Zsh shell function like this: dt () { t0=$EPOCHREALTIME "$@" printf "%.7f wallSec\n" "$((EPOCHREALTIME-t0))" >&2 } And then you can actually run in your shell dt echo hi, moon without even a single fork/clone. (which you can confirm with an off to the side `strace -fv -o/dev/shm/dt.st -p WHATEVER_PID`, although I guess the culture these days is often to have even prompt printing launch a zoo of activity)

michaelcampbell 1y ago
> These variables seem "under known". I speak only for me but TIL these; thanks!