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POCreating a FILE * stream that results in a string
 

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    <p>I'm looking for a way to pass in a <code>FILE *</code> to some function so that the function can write to it with <code>fprintf</code>. This is easy if I want the output to turn up in an actual file on disk, say. But what I'd like instead is to get all the output as a string (<code>char *</code>). The kind of API I'd like is:</p> <pre><code>/** Create a FILE object that will direct writes into an in-memory buffer. */ FILE *open_string_buffer(void); /** Get the combined string contents of a FILE created with open_string_buffer (result will be allocated using malloc). */ char *get_string_buffer(FILE *buf); /* Sample usage. */ FILE *buf; buf = open_string_buffer(); do_some_stuff(buf); /* do_some_stuff will use fprintf to write to buf */ char *str = get_string_buffer(buf); fclose(buf); free(str); </code></pre> <p>The <strong>glibc</strong> headers seem to indicate that a FILE can be set up with hook functions to perform the actual reading and writing. In my case I think I want the write hook to append a copy of the string to a linked list, and for there to be a <code>get_string_buffer</code> function that figures out the total length of the list, allocates memory for it, and then copies each item into it in the correct place.</p> <p>I'm aiming for something that can be passed to a function such as <code>do_some_stuff</code> without that function needing to know anything other than that it's got a <code>FILE *</code> it can write to.</p> <p>Is there an existing implementation of something like this? It seems like a useful and C-friendly thing to do -- assuming I'm right about the <code>FILE</code> extensibility.</p>
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