1<!-- 2Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al. 3 4SPDX-License-Identifier: curl 5--> 6 7# Parallel transfers 8 9curl 7.66.0 introduced support for doing multiple transfers simultaneously; in 10parallel. 11 12## -Z, --parallel 13 14When this command line option is used, curl performs the transfers given to it 15at the same time. It does up to `--parallel-max` concurrent transfers, with a 16default value of 50. 17 18## Progress meter 19 20The progress meter that is displayed when doing parallel transfers is 21completely different than the regular one used for each single transfer. 22 23 It shows: 24 25 o percent download (if known, which means *all* transfers need to have a 26 known size) 27 o percent upload (if known, with the same caveat as for download) 28 o total amount of downloaded data 29 o total amount of uploaded data 30 o number of transfers to perform 31 o number of concurrent transfers being transferred right now 32 o number of transfers queued up waiting to start 33 o total time all transfers are expected to take (if sizes are known) 34 o current time the transfers have spent so far 35 o estimated time left (if sizes are known) 36 o current transfer speed (the faster of upload/download speeds measured over 37 the last few seconds) 38 39Example: 40 41 DL% UL% Dled Uled Xfers Live Qd Total Current Left Speed 42 72 -- 37.9G 0 101 30 23 0:00:55 0:00:34 0:00:22 2752M 43 44## Behavior differences 45 46Connections are shared fine between different easy handles, but the 47"authentication contexts" are not. For example doing HTTP Digest auth with one 48handle for a particular transfer and then continue on with another handle that 49reuses the same connection, the second handle cannot send the necessary 50Authorization header at once since the context is only kept in the original 51easy handle. 52 53To fix this, the authorization state could be made possible to share with the 54share API as well, as a context per origin + path (realm?) basically. 55 56Visible in test 153, 1412 and more. 57
