FDTableViewer

Tool to display the tables used by the OS to keep track of open files, assignation of File Descriptors (FD) and processess.

• Process FD table
• System-wide FD Table
• Vnodes FD table
• Composed view of the previous tables

How to use the program

• To compile the code, run make in the terminal, and then run make clean to clean up the object files if needed.
• Type ./showFDtables to run the program in the terminal.
• Use --per-process, --systemWide, --Vnodes, --composite to display the appropriate tables. If none of these command line arguments are given, then the program displays all of the tables
• Enter the PID number of a process to see information only relating to that process, e.g. ./showFDtables 1001
• Use --threshold=N to show number of processes that have more than N files open
• Use --output_TXT and/or --output_binary to output to files in text or binary format respectively.

How did I solve the problem

• Used the 3rd-party libraries: "dirent.h, sys/stat.h, sys/types, unistd.h" to generate the data necessary.
• readlink to read the filename, stat for the inobe number, readdir and while loop to loop through the directories
• Used nested linked lists to store the data, a list of user processes, and then for each process a list of file descriptors associated with that process
• Then read the appropriate data from the data structure, and displayed it using fprintf to the console or written to a file
• Written modular code over 3 separate files:
  • showFDtables.c for main function and argument parsing
  • construct.c for constructing the data structure used to hold all the information about the FD table
  • display.c for reading the data stored in the data structure to display the appropriate tables to the console or write them to a file

Overview of functions

showFDtables.c

Contains the main function and argument parsing

• int is_number(char *number) - Checks whether all characters in the string are 0-9
• int arg_checker(int *flag_value, int default_value, int nondef_value, char *passed_string, char *true_string) - Checks whether the passed_string matches the true_string command line argument and assigns correct value to flag_value
• int value_arg(int *flag_value, int default_value, char *passed_string) - Checks whther passed_string is a number and assigns correct value to flag_value
• int arg_with_value_checker(int *flag_value, int default_value, char *passed_string, char *true_string_prefix) - Checks whether passed_string matches true_string_prefix and assigns correct mumerical value to flag_value, used for '--threshold=N'
• int main(int argc, char **argv) - Parses the command line arguments and makes the correct display call

construct.c

Constructs the data structure used to hold all the information about the FD table

• struct list_node *create_new_node(long key, void *data_head, void *data_tail) - Creates a new node of doubly-linked list
• void insert_at_tail(struct list_node **head, struct list_node **tail, struct list_node *new_node) - Performs the insertion of new_node at the tail of the list with O(1) complexity.
• void construct_fd_list(long pid, struct list_node **data_head, struct list_node **data_tail) - Construct list of file descriptors associated with the process
• void construct_data(struct list_node **data_head, struct list_node **data_tail) - Construct list of all user processes

display.c

Reads the data stored in the data structure to display the appropriate tables to the console or write them to a file

• void display_fd_helper(struct list_node *data_head, struct list_node *fd_head, int mode, int pid, int output_mode) - Helper function to output the table to console or write it to a file
• struct list_node *find_node(struct list_node *data_head, long key) - Find the node with specific PID
• void display_helper(struct list_node *data_head, int mode, int pid, int output_mode) - Helper function to display the table
• void display_per_process(struct list_node *data_head, int pid) - Displays the per-process table
• void display_systemWide(struct list_node *data_head, int pid) - Displays the SystemWide table
• void display_Vnodes(struct list_node *data_head, int pid) - Displays the Vnodes table
• void display_composite(struct list_node *data_head, int pid, int output_mode) - Displays the composite table
• void display_threshold(struct list_node *data_head, int threshold) - Displays the threshold
• void display(int per_process, int systemWide, int Vnodes, int composite, int threshold, int output_TXT, int output_binary, int pid) - displays the FD tables