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File Handles

Var-returning helpers for working with files. These wrap FILE * in an ABS_FILE object (see file-io.md for the raw C versions).

#include "abscom/abs.h"

API

Function Description
var fopen_safe(const char *filename, const char *mode) Open a file and return a handle var (or an ABS_ERROR).
var read_file(var file_obj) Read from the current position to end of file, as a string.
void write_file(var file_obj, var content) Write content (stringified if not a string) at the current position.
void close_file(var file_obj) Close the handle (sets the stored pointer to NULL). 
abs_init();

var f = fopen_safe("out.txt", "w");
write_file(f, v("line one\n"));
close_file(f);

var g = fopen_safe("out.txt", "r");
var contents = read_file(g);
close_file(g);
print(contents);               /* line one */

Notes

  • read_file seeks to the end before reading, so it reads the whole remaining file from wherever the cursor currently is.
  • fopen_safe returns ABS_ERROR ("Could not open file") when fopen fails.
  • read_file on a non-file returns ABS_ERROR; write_file/close_file on non-files are silent no-ops.
  • Forgetting close_file leaks the underlying FILE * — close handles when done.

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