Reference no: EM135112

The purpose of this program is to change such that it makes use of the IPC facilities provided by UNIX.

Master:

• Accepts command line inputs (N filenames and string to find).
• Forks "Reads Files,"(repeatedly, once for each input file) "Concatenate Text," and "Finds word."

Reads Files:
• Accepts command line inputs (1 filename, 1 pipe ID, 1 semaphore key, and 1 shared memory key).
• Reads text from the specified file and determines how big the file is.
• Creates a dynamic 1D array to hold the text.
• Strips repeating blanks from the text.
• Determines the resulting size of the text.
• Writes the new size into shared memory 1.
• Waits for semaphore 1to be set (by Concatenate Text program).
• Writes the text into pipe 1.
• Terminates.

NOTE -To terminate the entire process you can assume that the filename "EXIT" will be sent to this program. You can use this to set shared memory 1 to -1.

Concatenate Text:
• Accepts command line inputs (2 pipe IDs, 2 semaphore keys, and 2 shared memory keys).
• Waits for a non-zero value to be written into shared memory 1.
• Creates a dynamic 1D array large enough to concatenate the new text with any old text.
• Copies the old text into the new array.
• Sets semaphore 1.
• Set shared memory 1 to 0.
• Reads data from pipe 1.
• Concatenates the new data with the old.
• Waits for next data stream (non-zero in shared memory 1).

NOTE -If this program finds a -1 in shared memory 1 it will assume that all of the data to be concatenated has been sent. At this point this program will:
o Write the final text size into shared memory 2.
o Waits for semaphore 2 to be set (by Find Words).
o Writes resulting text into pipe 2.
o Terminates.

Find Words:
• Accepts command line inputs (1 pipe ID, 1 semaphore key, 1 shared memory key, and 1 string to find).
• Waits for a non-zero value to be written into shared memory 2.
• Creates a dynamic 2D array of characters (80xM) large enough to hold the combined text.
• Sets semaphore 2.
• Reads text from pipe 2.
• Searches for the text passed in by:
o Scans the 2D array (crossword like manner -by rows, by column, by diagonal) looking for the string.
o If the string is found, continue scanning the text in the same "direction"to find the secret message. Your program must print out this secret message.
• Terminates.