0x15-file_io

0x15. C - File I/O

0-read_textfile.c

Write a function that reads a text file and prints it to the POSIX standard output.

• Prototype: ssize_t read_textfile(const char *filename, size_t letters);
• Where letters is the number of letters it should read and print
• Returns the actual number of letters it could read and print
• If the file can not be opened or read, return 0
• If filename is NULL return 0
• If write fails or does not write the expected amount of bytes, return 0

1-create_file.c

Create a function that creates a file.

• Prototype: int create_file(const char *filename, char *text_content);
• Where filename is the name of the file to create and text_content is a NULL terminated string to write to the file
• Returns: 1 on success, -1 on failure (file can not be created, file can not be written, write “fails”, etc…)
• The created file must have those permissions: rw-------. If the file already exists, do not change the permissions.
• If the file already exists, truncate it
• If filename is NULL return -1
• If text_content is NULL create an empty file

2-append_text_to_file.c

Write a function that appends text at the end of a file.

• Prototype: int append_text_to_file(const char *filename, char *text_content);
• Where filename is the name of the file and text_content is the NULL terminated string to add at the end of the file
• Return: 1 on success and -1 on failure
• Do not create the file if it does not exist
• If filename is NULL return -1
• If text_content is NULL, do not add anything to the file. Return 1 if the file exists and -1 if the file does not exist or if you do not have the required permissions to write the files

3-cp.c

Write a program that copies the content of a file to another file.

• Usage: cp file_from file_to
• If the number of argument is not the correct one, exit with code 97 and print Usage: cp file_from file_to, followed by a new line, on the POSIX standard error
• If file_to already exists, truncate it
• If file_from does not exist, or if you can not read it, exit with code 98 and print Error: Can't read from file NAME_OF_THE_FILE, followed by a new line, on the POSIX standard error
  • Where NAME_OF_THE_FILE is the first argument passed to your program
• If you can not create or if write to file_to fails, exit with code 99 and print Error: Can't write to NAME_OF_THE_FILE, followed by a new line, on the POSIX standard error
  • Where NAME_OF_THE_FILE is the second argument passed to your program
• If you can not close a file descriptor, exit with code 100 and print Error: Can't close fd FD_VALUE, followed by a new line, on the POSIX standard error
  • Where FD_VALUE is the value of the file descriptor
• Permissions of the created file: rw-rw-r--. If the file already exists, do not change the permissions
• You must read 1,024 bytes at a time from the file_from to make less system calls. Use a buffer
• You are allowed to use dprintf