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ft_printf - Recoding printf() /42 Lisboa/

What is it about?

  • As my second project as a cadet at 42 Lisboa, I was in charge of recoding the libc's printf function, for it to have some of the same features as the original one.

  • That being said, my 'ft_printf' function is a custom implementation of the 'printf' function in C, that provides a similar interface for printing formatted output. It allows you to specify a format string and a list of arguments, and it generates output based on the format string.

In order to make it work, I had to work with the concept of variadic functions, which can somehow bring more flexibility to the programs that are built based on the C language.

How does it work?

  • The format string consists of text and format specifiers, which are special codes that specify how the corresponding argument should be formatted. Format specifiers start with a percent sign (%) and are followed by a letter that determines the type of the argument and the format of the output. For example, %d specifies that the corresponding argument is an integer and should be formatted as a decimal number.

  • Then, the function processes the format string character by character and performs the following actions:

    • if a character is not a format specifier, it is simply written to the output; or
    • if a character is a format specifier, the function retrieves the next argument from the argument list, formats it according to the specified format, and writes the result to the output.

  • On my implementation, the function processed the following type specifiers:

    • %c - single character

    • %s - string of characters

    • %p - pointer to void (in hexadecimal)

    • %d - decimal number

    • %i - integer number

    • %u - unsigned decimal number

    • %x - number in hexadecimal (lowercase)

    • %X - number in hexadecimal (uppercase)

    • %% - percent character

  • Once the function has processed the entire format string, it returns the number of characters written.

  • Note that 'ft_printf' is similar to 'printf', but not exactly the same. 'ft_printf' might have some differences in the way it handles format specifiers, escape sequences, and errors compared to printf.