步骤
1）下载curl包（可以在这个网站上找最新的版本 http://curl.haxx.se/download/）
wget https://curl.haxx.se/download/curl-7.55.1.tar.gz
2）解压
tar -xzvf curl-7.55.1.tar.gz
3）覆盖安装
1 cd curl-7.55.1
2 ./configure
3 make
4 make install
4）使用 curl --version 检查是否更新成功
根据这个步骤安装过程中，如出现错误，如下，是因为权限问题，使用sudo make install即可。
Making install in lib
make[1]: Entering directory '/home/qiao/install/curl-7.61.1/lib'
make[2]: Entering directory '/home/qiao/install/curl-7.61.1/lib'
/bin/mkdir -p '/usr/local/lib'
/bin/bash ../libtool --mode=install /usr/bin/install -c libcurl.la '/usr/local/lib'
libtool: install: /usr/bin/install -c .libs/libcurl.so.4.5.0 /usr/local/lib/libcurl.so.4.5.0
/usr/bin/install: cannot create regular file '/usr/local/lib/libcurl.so.4.5.0': Permission denied
Makefile:1068: recipe for target 'install-libLTLIBRARIES' failed
make[2]: *** [install-libLTLIBRARIES] Error 1
make[2]: Leaving directory '/home/qiao/install/curl-7.61.1/lib'
Makefile:3523: recipe for target 'install-am' failed
make[1]: *** [install-am] Error 2
make[1]: Leaving directory '/home/qiao/install/curl-7.61.1/lib'
Makefile:927: recipe for target 'install-recursive' failed
make: *** [install-recursive] Error 1
作者：柒月
