We can clearly see from the above output that our three wget commands are running in parallel. Why does curl work with a specific https site, but wget has problems with certificates? Now let us ask parallel to execute all the commands in that file simultaneously. If you want to quickly terminate GNU parallel, you can run fire up the below command. You have various options to run programs or commands in parallel on a Linux or Unix-like systems: => Use GNU/parallel or xargs command. How to send a header using a HTTP request through a curl call? Basically execute something/fetch information from all machines in a cluster. The curl command I used will store the output in 1.html.tmp and only if the curl command succeeds then it will be renamed to 1.html (by the mv command on the next line). You can now execute commands against these groups by calling the group name (web and db in our case). Let's first execute the wget example that we saw using GNU parallel. See below. To make it permanent, you can add it inside the user's .bashrc file as well. Making statements based on opinion; back them up with references or personal experience. Lines and paragraphs break automatically. Update: I suspect that my example with xargs could be improved (at least on Mac OS X and BSD with the -J flag). You can also creates a grouping of servers using the file /etc/clustershell/groups (if the file does not exist, then create it). How has the first atomic clock been calibrated? your coworkers to find and share information. See below. How to log outgoing http requests from PHP + cURL? The way I do things like this is with xargs, which is capable of running a specified number of commands in subprocesses. You can have as many of these curl processes running in parallel and sending their outputs to different files. Do I still need a resistor in this LED series design? You can clearly see the output is completely messed up(outputs of those three pings are mixed up). The official announcement of this feature from Daniel Stenberg is here: https://daniel.haxx.se/blog/2019/07/22/curl-goez-parallel/. It can be installed by the below commands (depending upon your Linux distribution). To run more downloads in parallel, give a higher value for –P, like 20, or 40. Why did Galileo express himself in terms of ratios when describing laws of accelerated motion? Just use the -O option (man curl for details). Really the best solution since it allows resuming failed downloads and uses 'make' which is both robust and available on any unix system. Is a lightfoot halfling obscured for the purposes of hiding while in the space of another creature? For example, if am executing this command as "ubuntu" user, then the private key used will be /home/ubuntu/.ssh/id_rsa. Just use the -O option (man curl for details). Which is then passed to xargs as input using the standard Linux pipe. We used -j option in our examples to override this default behavior. Therefore, 10 processes of curl are running in parallel. To demonstrate this, I have few junk files sitting in an object storage. http://www.commandlinefu.com/commands/view/3269/parallel-file-downloading-with-wget. (The -k switch tells make to keep downloading the rest of the files even if one single download should fail.). Following would start downloading in 3 process: so 4 downloadable lines of URLs are generated and sent to xargs.