Merge pull request flashreads#165 from waltherman/master

Create 014-curl-howto.md

linux/014-curl-howto.md

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+---
+id: 014-curl-howto.md
+title: curl command usage short guide
+tags: 
+  - linux
+  - curl
+author: waltherman
+meta-description: Curl is data transfer command. This is curl short command guide with examples
+date: 2021-10-14 03:40:00 +0300 
+keywords: linux, curl, url, data transfer, api testing
+template: post
+categories:
+  - linux
+cover: ../../images/categories/linux.png
+---
+
+# Curl
+
+Curl is a tool for data transfer. It supports a variety of protocols - HTTP, HTTPS, FTP, SFTP, TFTP, IMAP, POP3, SCP, SMTP and a bunch of other protocols, full list is available in man output.
+It is tiny, flexible, could provide verbose information, good for automation, since user interaction witch curl is not needed.
+
+## Curl usage
+
+Syntax is simple:
+```
+$ curl [options] [URL]
+```
+
+The basic request to GitHub would be look like:
+```
+$ curl github.com
+```
+Downloading files with the same name, as in the URL
+```
+$ curl -O [URL]
+```
+Or with specific file name:
+```
+$ curl -o [filename] [URL]
+```
+Continue downloading of stopped download is possible with "-C" parameter
+```
+$ curl -C -O [URL]
+```
+Verbose output
+```
+$ curl -v [options] [URL]
+$ curl --verbose [options] [URL]
+```
+Authenticate on remote server
+```
+$ curl -u {username}:{password} [URL]
+```
+For example, download FTP file with authentication would look like:
+```
+$ curl -u ftpuser16:Password111 -O ftp://example.com/bugrep.tgz
+```
+File upload:
+```
+$ curl -T -u {username}:{password} [URL]
+```
+
+Progress bar:
+It is possible to change curl meter to progress bar:
+```
+$ curl -# [URL]
+$ curl --progress-bar [URL]
+```
+
+Or disable any progress information:
+```
+$ curl -s [URL]
+$ curl --silent [URL]
+```
+
+HTTP and HTTPS:
+Include HTTPS headers to output
+```
+$ curl -i https://github.com
+$ curl --include https://github.com
+```
+Specify HTTP-request type:
+```
+$ curl --request [request type] [options] [URL]
+```
+Example
+```
+$ curl --request GET https://github.com
+```
+Proxy server also could be specified:
+```
+curl -x [proxy address]:[port] [URL]
+```
+If proxy server requires authentication, curl can be used with next command:
+```
+curl -x [proxy address]:[port] -U [user]:[password] [URL]
+curl -x [proxy address]:[port] --proxy-user [user]:[password] [URL]
+```
+
+SMTP
+If you do not like to send emails via telnet you could use curl 
+```
+$ curl –url [SMTP URL] –mail-from [sender address] –mail-rcpt [recipient address] -n –ssl-reqd -u {email}:{password} -T [mail text file]
+```