run multiple curl commands in parallel

Again, from a computer/CPU standpoint it mainly deals with one task at a time, but keeps on switching between tasks, which happens too fast, and we are perfectly fine as far as multiple tasks are progressing simultaneously. We simply pass the -b option to clush command against one of our group and we can interactively fire commands on these group. How can I trick programs to believe that a recorded video is what is captured from my MacBook Pro camera in realtime? One simple solution would be to send all jobs to the UNIX. And -P 2 tells xargs to keep 2 subprocesses running all the time, each one handling a single argument, until all of the input arguments have been processed. To be honest, I have not found GNU Parallel that user friendly, when it comes to remote command execution on a list of servers simultaneously. This switching between tasks happens so fast that it is very difficult for us to notice. If you have 100 commands to execute using GNU parallel, the jobs will be executed in smaller chunks. Below shown is an example to achieve just that. Also, is it possible for curl to write output of each URL to separate file say URL.html, where URL is the actual URL of the page under process. You can use GNU Parallel for some of the below use cases. In our below example, we have limited the number of jobs to 10, that will run in parallel. You could use something like the following In my test cases, some of these commands were not stable enough to recommend to execute against number of servers in parallel. The official announcement of this feature from Daniel Stenberg is here: Its called GNU Parallel. Let us fire up a command against our node[1-2] using pdsh. 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). Why can't modern fighter aircraft shoot down second world war bombers? Without specifying the RCMD environment variable, you can also run commands like the one shown below. How Does SSL/TLS Chain Certificates and Its Validation work? Just use the -O option (man curl for details). The first three commands wget commands will be executed in parallel. You can now imagine why we are under the illusion that multiple tasks are being executed at the same time. Update: I suspect that my example with xargs could be improved (at least on Mac OS X and BSD with the -J flag). How? What is the best way to execute 5 curl requests in parallel from a bash script? ab is a very simple yet effective tool of this type, which works for any web server … By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy. Does the order of the output matter to you? how to set the number of parallel downloads ? To learn more, see our tips on writing great answers. We used -j option in our examples to override this default behavior. Stack Overflow for Teams is a private, secure spot for you and You can use shortcuts, and regular expressions, if you have servers in the format of or something like that. Once all files have been successfully downloaded, make will report that there is nothing more to be done, so there is no harm in running it one extra time to be "safe". Here I am downloading pages from 1 to 10 and storing them in a file named 1.html. The -n 1 is there so that xargs only uses 1 line from the URLS.txt file per curl execution. Now let's try with parallel, and prevent the output from getting messed up. If you go one by one, it will consume a lot of time. How to reload .bash_profile from the command line? wget is just an example that we are using here for our tutorial. Now you can run as many commands as you like by using the script as shown below. As of 7.66.0, the curl utility finally has built-in support for parallel downloads of multiple URLs within a single non-blocking process, which should be much faster and more resource-efficient compared to xargs and background spawning, in most cases: This will download 18 links in parallel and write them out to 18 different files, also in parallel.

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