C CGI Library 1.1
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The library also has several handy data conversion functions. Each name and value is URL encoded as follows. Letters and digits cgi binary output signals not changed. You can easily convert a string to a numeric data type with the standard C library functions atoiatofstrtolstrtodetc.
And you can convert a numeric data type to a string with sprintf. Unfortunately, null terminated strings are not suitable for storing raw binary data, because a null byte in the data is mistaken for the string terminator. These functions make copies of strings as necessary so that after the function returns you cgi binary output signals safely do anything you want with any string that you have passed as a parameter.
Here is cgi binary output signals example program that outputs all of its CGI data. In your C source, include ccgi. If you are not uploading any files, then just pass it a null argument. The final six characters of the template string must be XXXXXX and mkstemp replaces these with random characters to create a new file with a unique name. If you pass a null or invalid template string, then uploaded file data is silently discarded. This returns an array of two strings provided no other form input tags are named uploadfield.
In value is the name of the uploaded file on the web server, which is derived from the template string. In value is the name of the file specified by the user in the browser. We use mkstemp to guarantee unique file names because a form may have multiple file upload fields, resulting in multiple files. Furthermore, multiple users can upload files to multiple instances of the CGI at the same time. Here is an example CGI program that uploads a file.
Many web applications pass cgi binary output signals data to the browser in cookies or form variables. Cgi binary output signals the browser passes this data back, the web application cannot tell if it has been tampered with. An attacker can easily handcraft a web request that includes forged cookies or forged form data. Raw encrypted output is binary. It decrypts the digest and the data, and recomputes the digest.
If the two digests match, then it returns the data. Otherwise it returns null to indicate failure. It is essentially impossible to tamper with the data without knowing the password. Of course the security of the data depends on the security of the password, which should be very difficult to guess and very difficult to steal. Usually when a web server receives a request for a CGI resource, the web server executes a CGI program, which handles the request and exits.
This does not perform well under cgi binary output signals load. The SCGI server responds to the web server, which forwards the response back to the user's browser. This is much more efficient than executing a CGI program for each cgi binary output signals. Under high load a SCGI server must be able to handle multiple requests concurrently. The SCGI server provided here pre forks a specified number of child processes that all wait for requests.
The parent process monitors how many child processes are busy and creates more if necessary. If too many processes are idle, then the parent terminates some of them. You provide the code that handles web requests in a callback function, which is called once for each request. The environment, standard input, and standard output are set up so that your callback can be written very much like a traditional CGI program. The SCGI server puts itself into the background, and forks child processes to handle web requests.
The web server does not automatically start the SCGI server program, so you must start it. You control which user account runs the SCGI server and what privileges it has. The callback function operates very much like a traditional CGI program, except that it gets called multiple times. When writing your callback consider the following.