Specify a file for writing protocol headers. Example: curl --dump-header store. Provide a path for the EGD socket. Specify an OpenSSL crypto engine. Request an ETag read from a file. Example: curl --etag-compare etag. Example: curl --etag-save etag. Maximum wait time for a continue response. Example: curl --expecttimeout 2.
Tell curl to fail and exit when it detects the first error in transfer. If the server returns an error with code or greater, curl saves the content and returns error If the server returns an error, curl fails silently and returns error Use false start on TLS handshake.
Similar to -F , --form , but the value strings are processed literally. Emulate a form with a Submit button that has been pressed. The sign forces the content to be a file. Specify the account data for the FTP server. Specify the command to be sent if the username and password authentication fails. If the specified directory does not exist, curl will attempt to create it.
Specify a method to be used for obtaining files over FTP. Available methods are multicwd , nocwd , and singlecwd. Use passive data connection mode. Reverse the default roles for the FTP connection. Do not use the IP address suggested by the server. Disable the URL globbing parser. Use the Happy Eyeballs algorithm for connecting to dual-stack hosts. Obtain only headers. Specify an additional header to be sent in the HTTP request.
See help for a specific category. Example: curl --help all. Pass a digit hexadecimal string. Enable HSTS. Example: curl --hsts cache.
Accept a HTTP version 0. Example: curl --http0. Use HTTP version 1. Example: curl --http1. Use HTTP version 2. Use this option if you know that the server supports this HTTP version.
Attempt to use HTTP version 2. Use HTTP version 3. This is an experimental option. Ignore the Content-Length header. Specify that the output should include the HTTP response headers. Allow curl to work with insecure connections. Specify the interface for performing an action. Only resolve names to IPv4 addresses. Only resolve names to IPv6 addresses. Discard session cookies. Example: curl --junk-session-cookies -b cookies. Specify the idle time for the connection before it sends keepalive probes.
Specify the type of the private key. Specify the file containing the private key. Enable and use Kerberos authentication. Available levels are clear , safe , confidential , and private default. Obtain C source code for the specified command line operation. Example: curl --libcurl client. Specify the maximum upload and download transfer rate.
Force a name-only view. Specify the port numbers to be used for the connection. Similar to -L , --location , but enables you to send name and password to all redirections. Allow curl to follow any redirections. Specify the login options for email server authentication. Provide a single address as the identity. Provide a single "from" address. An HTTP request has the option to include information about which address referred it to the actual page.
Curl allows you to specify the referrer to be used on the command line. It is especially useful to fool or trick stupid servers or CGI scripts that rely on that information being available or contain certain data. An HTTP request has the option to include information about the browser that generated the request. Curl allows it to be specified on the command line. It is especially useful to fool or trick stupid servers or CGI scripts that only accept certain browsers.
Cookies are generally used by web servers to keep state information at the client's side. Curl also has the ability to use previously received cookies in following sessions. If you get cookies from a server and store them in a file in a manner similar to:. While saving headers to a file is a working way to store cookies, it is however error-prone and not the preferred way to do this.
Instead, make curl save the incoming cookies using the well-known netscape cookie format like this:. Note that by specifying -b you enable the "cookie awareness" and with -L you can make curl follow a location: which often is used in combination with cookies. So that if a site sends cookies and a location, you can use a non-existing file to trigger the cookie awareness like:. Curl will determine what kind it is based on the file contents.
In the above command, curl will parse the header and store the cookies received from www. The file "empty. To read and write cookies from a netscape cookie file, you can set both -b and -c to use the same file:. The progress meter exists to show a user that something actually is happening. The different fields in the output have the following meaning:.
The - option will display a totally different progress bar that does not need much explanation! Curl allows the user to set the transfer speed conditions that must be met to let the transfer keep going. By using the switch -y and -Y you can make curl abort transfers if the transfer speed is below the specified lowest limit for a specified time.
To have curl abort the download if the speed is slower than bytes per second for 1 minute, run:. This can be used in combination with the overall time limit, so that the above operation must be completed in whole within 30 minutes:. Forcing curl not to transfer data faster than a given rate is also possible, which might be useful if you are using a limited bandwidth connection and you do not want your transfer to use all of it sometimes referred to as "bandwidth throttle".
When using the --limit-rate option, the transfer rate is regulated on a per-second basis, which will cause the total transfer speed to become lower than the given number. Sometimes of course substantially lower, if your transfer stalls during periods. Curl automatically tries to read the. The config file could be made up with normal command line switches, but you can also specify the long options without the dashes to make it more readable.
Comments can be used within the file. If the first letter on a line is a -symbol the rest of the line is treated as a comment. If you want the parameter to contain spaces, you must enclose the entire parameter within double quotes ". Whitespaces ARE significant at the end of lines, but all whitespace leading up to the first characters of each line are ignored.
Prevent curl from reading the default file by using -q as the first command line parameter, like:. Force curl to get and display a local help page in case it is invoked without URL by making a config file similar to:. If you set config file name to - it will read the config from stdin, which can be handy if you want to hide options from being visible in process tables etc:.
When using curl in your own programs, you may end up needing to pass on your own custom headers when getting a web page. To delete a file named deleteFile.
You can also modify the above command for any HTTP method to do the corresponding task. Above mentioned are the main uses of curl. But there might be difficulties which needed to be fought such as redirects, user authentication, SSL certificates, etc. This is done with the help of redirects HTTP packets with status codes in the range When the server is configured to serve for only certain individuals with credentials, they will be provided with username and password.
One can make login with the help of -u flag. If you want to impose a data transfer limit use —limit-rate flag. Following command tries to download the file with rate limit as 10K.
If you do not want to see the progress meter, just append the command with -s flag. Progress will not be shown for response directed for the terminal.
Do you remember the situations in which you need to give security certificate exception to visit some websites? If you trust the sources and you want to do a data transfer, you can ignore SSL certificate validation by using -k flag. But how do they know that we are using a specific kind of device? We can change this User Agent with -A flag. If the server needs some data such as token or API key, use -d flag to send the data. Data that needs to be sent should follow the flag in the command.
This is one of the ways by which you can send your form information. Cookies are some small information that allows maintaining a session with a stateless HTTP protocol. If you want to know more about Cookies, refer to this great resource. Note that -b flag only reads the cookie from the file. So if the server resends another cookie, you might need to use -c option to write them. Max Waterman Thank you for the -Z option very useful for mass file download.
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