# While we can, technically, use ‹nc› to talk to HTTP servers, it's
# not the most convenient thing to do. We will look at another
# utility, called ‹curl› (the project name is cURL, URL being short
# for ‘uniform resource locator’), which can, among other things,
# fetch data from HTTP servers. Unlike ‹nc›, it will construct
# headers, parse replies and do a whole bunch of other useful
# things, like SSL or POST request with relative ease.
#
# Please note that ‹curl› is not standard (but can be installed on
# most Unix systems).

# We can start by a simple ‹curl› invocation to fetch a document
# (the ‹-s› option tells ‹curl› to not print progress information to
# ‹stderr›):

echo fetch http://ix.io/1FWS
curl -s http://ix.io/1FWS
echo

# Out of the box, curl prints the document to ‹stdout› -- this is
# convenient if we want to process the output immediately using some
# shell magic. But if we prefer to have it stored in a file, we can
# use ‹curl -O›, which will select a filename for us:

echo fetch https://www.fi.muni.cz/index.html
test -f index.html && exit 1 # die if the file is already here
curl -s -O https://www.fi.muni.cz/index.html
test -f index.html || exit 1 # die if the file did not materialize
ls -hl index.html
rm index.html
echo

# The last option to ‹curl› (related to ‹GET› requests) to look at
# is ‹-L›, for ‘location‘. In some instances, the HTTP server may
# return a code like 301 which tells the client that they should be
# looking elsewhere. For instance:

echo fetch http://www.fi.muni.cz
curl -s http://www.fi.muni.cz
echo

# In this case, we get a 301 Moved Permanently, with the instruction
# to look at the encrypted version of the site (i.e.
# ‹https://www.fi.muni.cz›). Since we don't want to handle such
# matters ourselves, we can use curl -L which will automatically
# follow the redirect:

echo "fetch http://www.fi.muni.cz (with redirects)"
curl -s -L http://www.fi.muni.cz | wc -c

# That's for GET requests with cURL, let's go on to ‹curl-post.sh›.