C PROGRAMMING AND UNIX COMPILIER:

Project Description:

In this project, you will design and implement a program to perform any of the following commands on strings. The command is chosen by typing in the string in square brackets at the input prompt.

[new] New String: Prompts the user for a string and stores it as the current string. Initially the current string is empty.

[list] List: Prints the current string to the screen.

[append] Append: Prompts the user for a string and adds this string to the end of the current string.

[find] Find: Prompts the user for a string and checks to see if it exists as a sub-word in the current string. If so, prints out the number of times the string entered exists as a sub string.

[replace] Replace: Replace the current string with the output of the last string modification command.

[toggle] Toggle: Prints the current string by toggling the case, i.e., Convert upper case letter to lower case letter and vice versa.

[rev] Reverse: Print the current string in the reverse order, character by character.

[wrev] Word Reverse: Print the current string in the reverse order, word by word.

[stat] Statistics: Prints the statistics of the current string in terms of the length of the string, the number of words, the frequency of each letter of the alphabet, etc.

[help] Help: List the different commands and their descriptions.

[hist] History: Prints a list of the past N commands to screen.

[quit] Quit: Quits the program.

Project Design:

You program will print a welcome :message, and then display a prompt cmd> and wait for the user to enter a command. If the command is an empty command, i.e. the user presses the enter key, you need to display the prompt again on the next line. If the command is invalid, you need to display an error message.

In the beginning, the current string is empty. To start playing with strings, you need to use the new command to store a new string into the current string.

New

The new command is used to take from the user a new string to play with.

cmd> new

Enter new string: This is my first string

List

The list command will print out the current string to the screen. If the current string is empty, nothing will be displayed.

cmd> list

This is my first string

Append

The append command takes an argument string and appends it to the end of the current string. The appended string and the old current string are separated by a space. It changes the current string.

cmd> new

Enter new string: This is

cmd> append

Enter string to append: my first string

cmd> list

This is my first string

Before appending a string to the current string, you need to make sure that the length of the new string does not exceed the maximum length of the string (MAX_STR_LEN). If exceeded, an error message should be printed. (No need to provide the testing result on this, but should be considered in the program.)

Find

The find command takes an argument string and checks to see if it occurs as a substring in the current string. If then prints out the number of times it exists in the current string. The find command is case sensitive.

cmd> list

This is my first string

cmd> find

Enter sub string to find: is

The substring exists 2 times in the current string.

cmd> find

Enter sub string to find: w

The substring exists 0 times in the current string.

Toggle

The toggle command toggles the case of the current string and prints it to the screen. It doesnt change the current string.

cmd> toggle

tHIS IS MY FIRST STRING

cmd> list

This is my first string

Replace

The replace command takes the resulting string of the last command and copies it into the current string.

cmd> toggle

tHIS IS MY FIRST STRING

cmd> replace

cmd> list

tHIS IS MY FIRST STRING

cmd> toggle

This is my first string

cmd> list

tHIS IS MY FIRST STRING

Reverse

The reverse command prints the current string in reverse order character by character. It doesnt change the current string.

cmd> rev

gnirts tsrif ym si sihT

Statistics

The statistics command prints the statistics of the current string in terms of its length in characters, in words, and the frequency of the different characters in the string.

cmd> stat

Satistics:

length: 23

word: 5

Frequency:

frequency of f: 1

frequency of g: 1

frequency of h: 1

frequency of i: 4

frequency of m: 1

frequency of n: 1

frequency of r: 2

frequency of s: 4

frequency of t: 2

frequency of y: 1

frequency of T: 1

Word Reverse

The reverse command prints the current string in reverse order word by word. It doesnt change the current string.

cmd> wrev

string first my is This

Help

The help command prints a list of commands to the screen.

cmd> help

[new] Enter New String

[list] List Current String

[append] Append a String to the End of Current String

[find] Find a String in Current String

[replace] Replace Current String with Output of Last Command

[toggle] Toggle the Case of Current String

[rev] Print Current String in Reverse Order Character By Character

[wrev] Print Current String in Reverse Order Word By Word

[stat] Print Statistics of Current String

[help] Print This Help Screen

[hist] Print a History of Commands Entered

[quit] Quit Program

[palindrome] Check palindrome

History

The history command prints to the screen the last HISTORY_SIZE (defined as a preprocessor constant) commands entered by the user. Each time when a command is entered, you should update your history and the current history table size. If the history is full, you should discard the oldest history and insert the newest command into the history. Empty commands are not counted.

Quit

The quit command terminates the program.