Question

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Easiest way to get file's contents in C

My program reads files that span over many lines. I would like to hold the content of a file in a single string.

I don’t know the number of lines of my file before execution, however I have fixed a line size to MAX_LINE_LEN.

How can you do that?

Answer 1

The function fread() doesn’t care about line breaks. The following code reads the contents of input_file_name and saves them to the array file_contents:

char *file_contents;
long input_file_size;
FILE *input_file = fopen(input_file_name, "rb");
fseek(input_file, 0, SEEK_END);
input_file_size = ftell(input_file);
rewind(input_file);
file_contents = malloc(input_file_size * (sizeof(char)));
fread(file_contents, sizeof(char), input_file_size, input_file);
fclose(input_file);

You can only make a string of this array if input_file_name contains the \0 character. If it does not, change the last three lines to:

file_contents = malloc((input_file_size + 1) * (sizeof(char)));
fread(file_contents, sizeof(char), input_file_size, input_file);
fclose(input_file);
file_contents[input_file_size] = 0;