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#ifndef _SHELL_H_

#define _SHELL_H_

#include <stdbool.h>

#define SUCCESS 0

#define ERROR -1

#define EXIT 1

#define DEBUG 0

#define MAX_ARG_LEN 100

typedef struct {

int argc; // total number of arguments

char** argv; // argument values (must malloc)

} command_t;

/* ------------------------------------------------------------------------------

*

* YOU NEED TO COMPLETE THIS FUNCTION.

*

* Allocate memory for the command. The last element in `p_cmd->argv` should be

* NULL.

*

* The length of `p_cmd->argv` should be `argc+1`: the first `argc` slots are

* used to store the arguments and the last one is set to NULL.

*

* Arguments:

* p_cmd : pointer to the command need to allocate memory.

* argc : the number of arguments.

*

* Return:

* None

*/

void alloc_mem_for_command(command_t* p_cmd, int argc);

/* ------------------------------------------------------------------------------

*

* YOU NEED TO COMPLETE THIS FUNCTION.

*

* This function is used to free memory that may be malloc'd for the name and

* argv fields in the command_t structure. To be safe, you should also set the

* pointer values to NULL.

*

* HINT(s): See man page for more information about free function

*

* Arguments:

* p_cmd : pointer to a command_t structure

* Return:

* None

*

*/

void cleanup(command_t* p_cmd);

/* ------------------------------------------------------------------------------

*

* YOU NEED TO COMPLETE THIS FUNCTION.

*

* This function will parse the command (cmd for short) and its arguments

* specified by the user.

*

* HINT(s): This function is "essentially" an exercise in string parsing.

*

* EXAMPLE#1, if the user enters

*

* cd /mnt/cdrom

*

* at the shell prompt, line would contain "cd /mnt/cdrom".

* Using the space character as the delimiter, the fields in

* the command struct would be:

*

* - argc = 2

* - argv = {"cd", "/mnt/cdrom", NULL}

*

* EXAMPLE#2, if the user enters

*

* ls -la

*

* at the shell prompt, line would contain "ls -la". Using the

* space character as the delimiter, the fields in the command

* struct would be:

*

* - argc = 2

* - argv = {"ls", "-la", NULL}

*

* EXAMPLE#3, if the user enters nothing at the shell prompt (i.e.

* simply hits the return key), line would NULL, and the fields in

* the command struct would be:

*

* - argc = 0

* - argv = {NULL}

*

* Arguments:

* line: pointer to the string contains the cmd.

* p_cmd: pointer to the command_t structure

*

* Return:

* N/A

*

*/

void parse(char* line, command_t* p_cmd);

/* ------------------------------------------------------------------------------

*

* YOU NEED TO COMPLETE THIS FUNCTION.

*

* This function is used determine if the named command (cmd for short) entered

* by the user in the shell can be found in one of the folders defined in the

* PATH environment (env or short) variable. If the file exists, then the name

* of the executable at argv[0] is replaced with the location (fully qualified

* path) of the executable.

*

* For example,

*

* if command_t.argv[0] is "ls", and "ls" is in the "/usr/bin" folder,

* then command_t.argv[0] would be changed to "/usr/bin/ls"

*

* HINT(s): Use getenv() system function to retrieve the folders defined in the

* PATH variable. An small code segment is shown below that

* demonstrates how to retrieve folders defined in your PATH.

*

* char* path_env_variable;

* path_env_variable = getenv( "PATH" );

* printf("PATH = %s\n", path_env_variable );

*

* The format of the PATH is very simple, the ':' character is

* delimiter, i.e. used to mark the beginning and end of a folder defined in the

* path.

*

* Write a loop that parses each folder defined in the path,

* then uses this folder along with the stat function (see "File/Directory

* Status" section in the assignment PDF).

*

* Arguments:

* p_cmd: pointer to the command_t structure

* Return:

* true: if cmd is in the PATH

* false: if not in the PATH.

*

*/

bool find_fullpath(command_t* p_cmd);

/* ------------------------------------------------------------------------------

*

* YOU NEED TO COMPLETE THIS FUNCTION.

*

* This function will execute commands (cmd for short).

*

*

* Arguments:

* p_cmd: pointer to the command_t structure.

*

* Return:

* SUCCESS: successfully execute the command.

* ERROR: error occurred.

*

*/

int execute(command_t* p_cmd);

/* ------------------------------------------------------------------------------

*

* This function will determine if command (cmd for short) entered in the shell

* by the user is a valid builtin command.

*

* HINT(s): Use valid_builtin_commands array defined in shell.c

*

* Arguments:

* p_cmd: pointer to the command_t structure

* Return:

* true: the cmd is in array `valid_builtin_commands`.

* false: not in array `valid_builtin_commands`.

*

*/

bool is_builtin(command_t* p_cmd);

/* ------------------------------------------------------------------------------

*

* This function is used execute built-in commands such as change directory (cd)

*

* HINT(s): See man page for more information about chdir function

*

* Arguments:

* p_cmd: pointer to the command_t structure

* Return:

* SUCCESS: no error occurred during chdir operation.

* ERROR: an error occured during chdir operation.

*

*/

int do_builtin(command_t* p_cmd);

#endif // _SHELL_H_