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file IO - reading an entire file into memory return to main index #include <stdio.h>

Often the exact structure of a document is NOT know at the time it is read. Therefore, a function such as fscanf() cannot be used because the sequence, and type, of the data must be know beforehand!  Reading text one line at a time can also be tricky unless the maximum number of characters on a line is also known beforehand!  Often the only way to deal with text, especially when it contains numeric values in unknown locations is to read it in a single block, as shown here, or read it in small chunks and use a technique called "parsing". This reference shows how an entire text file can be read into memory. Parsing is dealt with in another web page.

/* declare a file pointer */ FILE *infile; char *buffer; long numbytes; /* open an existing file for reading */ infile = fopen("test.rib", "r"); /* quit if the file does not exist */ if(infile == NULL) return 1; /* Get the number of bytes */ fseek(infile, 0L, SEEK_END); numbytes = ftell(infile); /* reset the file position indicator to the beginning of the file */ fseek(infile, 0L, SEEK_SET); /* grab sufficient memory for the buffer to hold the text */ buffer = (char*)calloc(numbytes, sizeof(char)); /* memory error */ if(buffer == NULL) return 1; /* copy all the text into the buffer */ fread(buffer, sizeof(char), numbytes, infile); fclose(infile); /* confirm we have read the file by outputing it to the console */ printf("The file called test.dat contains this text\n\n%s", buffer); /* free the memory we used for the buffer */ free(buffer);

Once the buffer has been filled with a copy of the text from the source file it can used for operations such data extraction, searching/replacing and outputing to another file. More about that later!  For a full listing of this code refer to 4_IO_readall.c

http://www.fundza.com/c4serious/fileIO_reading_all/index.html