Buffered File I/O Summary

Specifier format: %w.pt (width, precision, data type)

Specifier types:

d, i integer in decimal format

o integer in octal format

x integer in hexadecimal format

u unsigned integer in decimal format

c integer in character format

s char *; prints all characters until the '\0'

f double [-]m.dddddd – by default 6 decimal places

e, E double [-]m.dddddde±xx or mddddddE±xx

g, G double; uses (e, E) if exponent is less than -4 or greater than or equal to precision; otherwise uses f format.

scanf also uses set [ ] or everything but the set with [^ ].

File Pointer creation: File *fp

File opening modes: r, w, a, rb, wb, ab (b = binary) (r = read; w = write; a = append)

Open command: fopen(filename, opening mode);

· returns a pointer to the file or NULL if cannot open

· Sample: FILE *ifp

if ((ifp = fopen(ifilename, "r")) == NULL) {
fprintf(stderr, "Cannot open %s\n", ifilename); }

Close command: fclose(fp);

Text File read / write commands:

Screen commands	File commands
putchar(c);	putc(fp, c);
getchar();	getc(fp);
printf("…", …);	fprintf(fp, "…", …);
scanf("…", …);	fscanf(fp, "…", …);
gets(s);	fgets(fp, max size, s)
puts(s);	fputs(fp, s);

Binary File read / write commands:

· fread: (pointer to read_buffer_var, object size, # objects, file pointer)

o Ex: fread(&person, sizeof(person), 1, ifp) >= 1

o Returns number read

· Fwrite: (pointer to write_buffer_var, object size, # objects, file pointer)

o fwrite(&person, sizeof(person), 1, ofp);

o returns number written