The URL syntax is protocol-dependent. You'll find a detailed
description in RFC 3986.
You can specify multiple URLs or parts of URLs by writing part
sets within braces and quoting the URL as in:
"http://site.{one,two,three}.com"
or you can get sequences of alphanumeric series by using [] as
in:
"ftp://ftp.example.com/file[1-100].txt"
"ftp://ftp.example.com/file[001-100].txt" (with leading
zeros)
"ftp://ftp.example.com/file[a-z].txt"
Nested sequences are not supported, but you can use several ones
next to each other:
"http://example.com/archive[1996-1999]/vol[1-4]/part{a,b,c}.html"
You can specify any amount of URLs on the command line. They will
be fetched in a sequential manner in the specified order. You can
specify command line options and URLs mixed and in any order on
the command line.
You can specify a step counter for the ranges to get every Nth
number or letter:
"http://example.com/file[1-100:10].txt"
"http://example.com/file[a-z:2].txt"
When using [] or {} sequences when invoked from a command line
prompt, you probably have to put the full URL within double
quotes to avoid the shell from interfering with it. This also
goes for other characters treated special, like for example '&',
'?' and '*'.
Provide the IPv6 zone index in the URL with an escaped percentage
sign and the interface name. Like in
"http://[fe80::3%25eth0]/"
If you specify URL without protocol:// prefix, curl will attempt
to guess what protocol you might want. It will then default to
HTTP but try other protocols based on often-used host name
prefixes. For example, for host names starting with "ftp." curl
will assume you want to speak FTP.
curl will do its best to use what you pass to it as a URL. It is
not trying to validate it as a syntactically correct URL by any
means but is instead very liberal with what it accepts.
curl will attempt to re-use connections for multiple file
transfers, so that getting many files from the same server will
not do multiple connects / handshakes. This improves speed. Of
course this is only done on files specified on a single command
line and cannot be used between separate curl invocations.
