bdekonin/get_next_line

This guide explains how to write an algorithm to read a line from a file descriptor using the read system call.

Get_next_line

This guide explains how to write an algorithm to read a line from a file descriptor using the read system call.

Prerequisites

• Knowledge of the read system call and its parameters
• Familiarity with file descriptors

Algorithm

1. Set up the read system call, passing in a file descriptor, a buffer and a byte count.
2. Create a loop that keeps running until the byte count is reached.
3. Read the next byte from the file descriptor.
4. Check if the byte is a newline character.
   • If so, break out of the loop
   • If not, add this byte to the buffer.
5. Return the buffer with the line read from the file descriptor.

Conclusion

Using the read system call, you can write an algorithm to read a line from a file descriptor. This guide has provided an overview of the steps required to achieve this.

Usage

Add the code below in the root of this project. Change textfile.txt to a file you want to read.

int main()
{
  int fd;
  int ret;
  char *line;
  
  fd = open("textfile.txt", O_RDONLY);
  ret = 1;
  while (ret > 0)
  {
    ret = get_next_line(fd, &line);
    printf("ret = [%i]\t[%s]", ret, line);
    free(line);
  }
  return (ret);
}

After running this it will print out the file line by line freeing every line it had read.