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curl
curl(1) is a command-line tool for fetching internet (chiefly web or FTP) content.
Tips
Suppressing Progress Bar
curl --no-progress-meter https://example.com
Downloading a File
curl --output path/to/file --fail https://example.com
In the case of a server error (HTTP 4xx), an error page is often returned by the server. The --fail option suppresses this page from output and causes curl(1) to exit with code 22.
Checking Availability
code=$(curl --no-progress-meter --output /dev/null --fail --head --write-out '%{http_code}' https://example.com)
case $code in
0)
echo "Success! Server returned HTTP code ${code}"
;;
22)
echo "Error! Server returned HTTP code ${code}"
;;
6)
echo "Error! Server not found"
;;
60)
echo "Error! SSL/TLS certificate cannot be verified"
;;
*)
echo "Error!"
;;
esacThe --head option causes curl(1) to only fetch only headers. The --write-out option takes a format string that will be populated with available variables.
Other useful variables:
Name |
Contains |
content_type |
Content type of the document |
http_version |
Version of HTTP that was used |
size_header |
Number of bytes in downloaded headers |
size_download |
Number of bytes in downloaded body and data (i.e. not headers) |
time_namelookup |
Number of seconds from start until name was resolved |
time_connect |
Number of seconds from start until TCP connection |
time_appconnect |
Number of seconds from start until SSL handshake |
time_pretransfer |
Number of seconds from start until all pre-transfer steps are complete |
time_starttransfer |
Number of seconds from start until first transferred byte is received |
time_total |
Number of seconds |
speed_download |
Average number of bytes per second |
ssl_verify_result |
Result of SSL verification (0 if successful) |