Add content of a text file to array in Bash - arrays

Question

I am trying to execute a curl for 300 at a same time and using array. I do not know how to bring the content of my file in array. The code I write is bellow.
array=();
for i in {1..300}; do
array+=( file.txt ) ;
done;
curl "${array[#]}";
The file.text include the following code
--next 'https://d16.server.com/easy/api/OmsOrder' -H 'Connection: keep-
alive' - H 'Pragma: no-cache' -H 'Cache-Control: no-cache' -H 'Accept:
application/json,
text/plain, */*' -H 'Sec-Fetch-Dest: empty' -H 'User-Agent: Mozilla/5.0
(Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/537.36 (KHTML, like Gecko)
Chrome/80.0.3987.132 Safari/537.36' -H 'Content-Type: application/json' -H
'Origin: https://d.server.com' -H 'Sec-Fetch-Site: same-site' -H
'Sec-Fetch-Mode: cors' -H 'Referer: https://d.server.com/' -H 'Accept-
Language: en-US,en;q=0.9,fa;q=0.8' --data-binary
'{"isin":"IRO3TPEZ0001","financeId":1,"quantity":50000,"price":5400}' --
compressed"

Answer 1

array=();
for i in {1..300}; do
array+=( $(cat file.txt|head -$i | tail -1) );
done;
curl "${array[#]}";

Answer 2

You have a file with shell formatted words that you are trying to repeat over and over in a command.
Since the words are shell formatted, you'll need to interpret them using e.g. eval:
contents=$(< file.txt)
eval "words=( $contents )"
arguments=()
for i in {1..300}
do
arguments+=( "${words[#]}" )
done
curl "${arguments[#]}"
A more robust design would be to not use shell quoting and instead format one argument per line:
--next
https://d16.server.com/easy/api/OmsOrder
-H
Connection: keep-alive
-H
Pragma: no-cache
You can then use the above code and replace the eval line with:
mapfile -t words < file.txt

Answer 3

The answer to this question should have been "put each request into a file, one option per line, and use -K/--config to include the file into the command line." That certainly should allow for 300 requests in a single curl command without exceeding the limit on the size of a shell command. (By "request" here, I mean "a URL with associated options". If you only want to use 300 URLs without modifying any other option, you can easily do that by just listing the URLs, on the command line if they aren't too long or otherwise in a file.)
Unfortunately, it doesn't work. I believe that it is supposed to work, and the fact that it doesn't is a bug. If you specify multiple -K options and each of them refers to a file which includes one request and the --next option, then curl will execute only the first and last file. If you instead put the --next options on the command-line in between the -K options, all the request options will be merged, and in addition curl will complain about a missing URL.
However, you can use the -K option by concatenating all 300 requests and passing them through stdin, using -K - to read from stdin. To test that, I created the file containing a single request:
$ cat post-req
--next
-H "Connection: keep-alive"
-H "Pragma: no-cache"
-H "Cache-Control: no-cache"
-H "Accept: application/json, text/plain, */*"
-H "Sec-Fetch-Dest: empty"
-H "User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10_15_3) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/80.0.3987.132 Safari/537.36"
-H "Content-Type: application/json"
-H "Origin: https://d.server.com"
-H "Sec-Fetch-Site: same-site"
-H "Sec-Fetch-Mode: cors"
-H "Referer: https://d.server.com/"
-H "Accept-Language: en-US,en;q=0.9,fa;q=0.8"
--data-binary "{\"isin\":\"IRO3TPEZ0001\",\"financeId\":1,\"quantity\":50000,\"price\":5400}"
--compressed
--url "http://localhost/foo"
and then set up a little webserver that just returns the requested path, and invoked curl with:
for i in $(seq 300); do cat post-req; done | curl -K -
Indeed, all three hundred requests are passed through.
For what it's worth, I reported the bug as https://github.com/curl/curl/issues/5120, and many thanks to Daniel Stenberg for being incredibly responsive by committing a fix in less than two days. So probably the issue will be resolved in the next curl release.