Por que redirecionar a saída para um arquivo produz uma tabela?

Question

Eu gostaria de configurar um cron job para registrar periodicamente uma medição. Um cartão de memória USB está instalado em um roteador:

user@router:/tmp/home/root# uname -a

Linux router 2.6.36.4brcmarm #2 SMP PREEMPT Sun Mar 20 16:06:18 EDT 2016 armv7l GNU/Linux

user@router:/tmp/home/root# curl http://THERMOSTAT/tstat/humidity  >> /tmp/mnt/USBstick/CT80_data/C14HumidityData.txt

  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100    18    0    18    0     0     80      0 --:--:-- --:--:-- --:--:--    83

Por que o acréscimo (> >) da saída a um arquivo produz a tabela acima?

A tabela não é produzida quando não está anexando:

curl http://THERMOSTAT/tstat/humidity
{"humidity":51.00}

Existe uma opção de comando para suprimir a resposta da tabela?

    

Answer 1

O medidor de progresso da onda . De man curl

PROGRESS METER
   curl  normally displays a progress meter during operations, indicating the
   amount of transferred data, transfer speeds and estimated time left,  etc.
   The  progress  meter  displays number of bytes and the speeds are in bytes
   per second. The suffixes (k, M, G, T, P) are 1024 based. For example 1k is
   1024 bytes. 1M is 1048576 bytes.

   curl  displays this data to the terminal by default, so if you invoke curl
   to do an operation and it is about to write data to the terminal, it  dis‐
   ables  the  progress meter as otherwise it would mess up the output mixing
   progress meter and response data.

   If you want a progress meter for HTTP POST or PUT requests,  you  need  to
   redirect  the  response  output  to  a file, using shell redirect (>), -o,
   --output or similar.

   It is not the same case for FTP upload as that operation does not spit out
   any response data to the terminal.

   If  you  prefer  a  progress  "bar"  instead  of  the  regular  meter, -#,
   --progress-bar is your friend. You can also  disable  the  progress  meter
   completely with the -s, --silent option.