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0x11. C - printf

Resource

Description

  • The function _printf writes output to stdout. The function writes under the control of a format string that specifies how subsequent arguments (accessed via the variable-length argument facilities of standard library stdarg) are converted for output.

  • Prototype: int _printf(const char *format, ...);

Return

  • Upon success, _printf returns the number of characters printed (excluding the terminating null byte used to end output to strings). If an output error is encountered, the function returns -1.

Format of the Argument String

  • The format string argument is a constant character string composed of zero or more directives: ordinary characters (apart from %) which are copied unchanged to the output stream; and conversion specifications, each of which results in fetching zero or more subsequent arguments.
  • Conversion specification is introduced by the character % and ends with a conversion specifier (which in whole make up the format specifier.)

General Requirements

  • All your files will be compiled on Ubuntu 20.04 LTS using gcc, using the options -Wall -Werror -Wextra -pedantic -std=gnu89
  • All your files should end with a new line.
  • No more than 5 functions per file.
  • You are not allowed to use global variables.
  • The prototypes of all your functions should be included in your header file called main.h`
  • All your header files should be include guarded.

Authorized functions and macros

  • write (man 2 write)
  • malloc (man 3 malloc)
  • free (man 3 free)
  • va_start (man 3 va_start)
  • va_end (man 3 va_end)
  • va_copy (man 3 va_copy)
  • va_arg (man 3 va_arg)

Github

  • There should be one project repository per group. If you clone/fork/whatever a project repository with the same name before the second deadline, you risk a 0% score.

Compilation

  • The code can be compiled like this: 
     gcc -Wall -Werror -Wextra -pedantic -std=gnu89 test/main.c *.c -o print
  • All test files will be in the test directory.

Authors

  • lex_xenda [@atogebaniaalexander]
  • nii_Okantey @kantey

Tasks

  1. I'm not going anywhere. You can print that wherever you want to. I'm here and I'm a Spur for life : A function that produces output according to a format.

    • Prototype: int _printf(const char *format, ...);
    • Returns: the number of characters printed (excluding the null byte used to end output to strings)
    • write output to stdout, the standard output stream
    • format is a character string. The format string is composed of zero or more directives. See man 3 printf for more detail. You need to handle the following conversion specifiers:
      • c
      • s
      • %
    • You don’t have to reproduce the buffer handling of the C library printf function.
    • You don’t have to handle the flag characters.
    • You don’t have to handle field width.
    • You don’t have to handle precision.
    • You don’t have to handle the length modifiers.

  2. Education is when you read the fine print. Experience is what you get if you don't : Handle the following conversion specifiers:

    • d
    • i
    • You don’t have to handle the flag characters.
    • You don’t have to handle field width.
    • You don’t have to handle precision.
    • You don’t have to handle the length modifiers.

  3. Just because it's in print doesn't mean it's the gospel : Create a man page for your function.

    • How to read the man page: man ./man_3_printf

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