Editing Web server (section)

=== Common tasks ===
A web server program, when it is running, usually performs several general '''tasks''', (e.g.):<ref name="web-server-technology" />
* starts, optionally reads and applies settings found in its [[configuration file]](s) or elsewhere, optionally opens log file, starts listening to client connections / requests;
* optionally tries to adapt its general behavior according to its settings and its current [[#Operating conditions|operating conditions]];
* manages '''client connection(s)''' (accepting new ones or closing the existing ones as required);
* '''[[#Read request message|receives]]''' client requests (by reading HTTP messages):
** reads and verify each HTTP request message;
** usually performs [[#URL normalization|URL normalization]];
** usually performs [[#URL mapping|URL mapping]] (which may default to URL path translation);
** usually performs [[#URL path translation to file system|URL path translation]] along with various security checks;
* '''[[#Manage request message|executes]]''' or refuses requested HTTP method:
** optionally manages [[#URL authorization|URL authorization]]s;
** optionally manages [[#URL redirection|URL redirection]]s;
** optionally manages requests for '''[[#Serve static content|static resources]]''' (file contents):
*** optionally manages [[#Directory index files|directory index files]];
*** optionally manages [[#Regular files|regular files]];
** optionally manages requests for '''[[#Serve dynamic content|dynamic resources]]''':
*** optionally manages [[#Directory listings|directory listings]];
*** optionally manages [[#Program or module processing|program or module processing]], checking the availability, the start and eventually the stop of the execution of external programs used to generate dynamic content;
*** optionally manages the communications with external programs / internal modules used to generate dynamic content;
* '''[[#Send response message|replies]]''' to client requests sending proper HTTP responses (e.g. requested resources or error messages) eventually verifying or adding [[HTTP headers]] to those sent by dynamic programs / modules;
* optionally '''logs''' (partially or totally) '''client requests and/or its responses''' to an external user log file or to a system log file by [[syslog]], usually using [[Common Log Format|common log format]];
* optionally '''logs process messages''' about '''detected anomalies or other notable events''' (e.g. in client requests or in its internal functioning) using syslog or some other system facilities;  these log messages usually have a debug, warning, error, alert level which can be filtered (not logged) depending on some settings, see also [[Syslog#Severity level|severity level]];
* optionally generates '''statistics''' about web traffic managed and/or its performances;
* other custom tasks.