Error code 400 while downloading a file via REST API

I can think of one workaround.

/mgmt/shared/iapp/file-management/

/var/config/rest/iapps/

/var/config/rest/iapps/sat/sat.txt

curl https:///mgmt/shared/iapp/file-management/sat/sat.txt

You can use the

/mgmt/tm/util/bash

cat

curl https:///mgmt/tm/util/bash \
  -X POST -H "Content-Type: application/json" \
  -d "{\"command\":\"run\", \"utilCmdArgs\": \"-c 'cat /tmp/sat.txt'\"}"

The response looks like this (The bold part is the file content: 5 lines of text. Note that LF is represented as the literal \n (0x5c 0x6e)):

{"kind":"tm:util:bash:runstate","command":"run","utilCmdArgs":"-c 'cat /tmp/sat.txt'","commandResult":"Line 1\nLine 2\nLine 3\nLine 4\nLine 5\n"}

The maximum octets you can download using the

/mgmt/tm/asm/file-transfer/downloads/file

When you need to download a file larger than this limit, download chunk by chunk by using the

Content-Range

GET /mgmt/tm/asm/file-transfer/downloads/file > file     ... first 1 MiB
GET /mgmt/tm/asm/file-transfer/downloads/file -H "Content-Range: 1048576-2097151/3165860"
>> file     ... next 1 MiB
GET /mgmt/tm/asm/file-transfer/downloads/file -H "Content-Range: 2097152-3165860/3165860" >> file    ... the remaining octets

See also Demystifying iControl REST Part 5: Transferring Files for the Content-Range header format.

after receiving this file how can be store it to read it? does storing in *.txt format work ?

As shown above, >> (double redirect) should append the data (HTTP response) to the file. If you are using curl, -o (hyphen o) option is also handy.

Regarding the file extension, it depends on the type of file (data) you download. If you are downloading an jpeg image, then its' natural to add the .jpg extension to the filename and open with an image viewer (although Unix does not rely upon file extensions, I personally prefer to add appropriate one). If the data is text, yes, use .txt and open with an text editor of your choice.

Related question:

API Calls to F5 limited to 1024 KB download