(libc.info.gz) Dynamic String Input

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(libc.info.gz) String Input Conversions

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 12.14.6 Dynamically Allocating String Conversions
 -------------------------------------------------
 
 A GNU extension to formatted input lets you safely read a string with no
 maximum size.  Using this feature, you don't supply a buffer; instead,
 `scanf' allocates a buffer big enough to hold the data and gives you
 its address.  To use this feature, write `a' as a flag character, as in
 `%as' or `%a[0-9a-z]'.
 
    The pointer argument you supply for where to store the input should
 have type `char **'.  The `scanf' function allocates a buffer and
 stores its address in the word that the argument points to.  You should
 free the buffer with `free' when you no longer need it.
 
    Here is an example of using the `a' flag with the `%[...]'
 conversion specification to read a "variable assignment" of the form
 `VARIABLE = VALUE'.
 
      {
        char *variable, *value;
 
        if (2 > scanf ("%a[a-zA-Z0-9] = %a[^\n]\n",
                       &variable, &value))
          {
            invalid_input_error ();
            return 0;
          }
 
        ...
      }
 

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(libc.info.gz) String Input Conversions

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