Submitting Your Work

$ submit 2031 lab2 prog.c

The Programs

1. Write a C program called numberLines1.c. It should copy standard input to standard output a line at a time and number the output lines. Do not use the readlines function from the text; it is there to make certain things clear to the reader, not to replace existing C library functions. Use fgets and fputs (and anything else you need).
   
   The output lines should be numbered like this:

   0001 xxxxxxx
   0002 xxxxxxx
   ...
   0010 xxxxxxx
   0011 xxxxxxx
   ...
   0999 xxxxxxx
   1000 xxxxxxx
   ...
   

   You can assume that there are fewer than 10,000 lines in the input. The line number should be followed by a single blank, then by the line itself as shown above.
   
   For this exercise, do not use a large buffer for reading/writing. Use a buffer of size 20. You can assume that no line is longer than 19 characters, including the newline character '\n' at the end of the line.


2. Write a C program called numberLines2.c. Its task is the same as that for the previous question, except that you cannot make any assumptions about the length of the lines that are being read. Nevertheless, you should still use a buffer of size 20.
   


3. Write a C program called reverse.c. It should read standard input a (string) token at a time. Each token it reads should be output alone on a line, but written backwards, as in the following example (the dollar sign $ is the Bourne shell prompt).

   $
   $ cat someStrings
   here
           are
                   some
   strings
   $
   $ reverse < someStrings
   ereh
   era
   emos
   sgnirts
   $
   $
   

   The file reverse.c should contain a main method and a separate method void reverse(char string[]). The reverse function should not use any auxillary data structures; for example, it should not try to do anything like copying its string argument into an array and then copying the array backwards into the string.
   
   For this exercise, assume that none of the strings read is longer than 29 characters (not counting the '\0' that will be appended by the scanf() function).
   
   See the man page entry for the C-library strlen function.


4. Write a C program called palindrome.c that reads from standard input and writes to standard output. Your program should copy to standard output all input tokens that are palindromes. No other output should be produced. You can assume that no input token is longer than 30 bytes.
   
   Each token that is a palindrome should be output alone on a line, as in the following example (the dollar sign $ is the Bourne shell prompt).

   $ cat someStings
   hello
           ollo
   I               a
   aaa
   
   aye madam aye
   eye madam eye
   
   
   $ palindrome < someStings
   ollo
   I
   a
   aaa
   madam
   eye
   madam
   eye
   $
   



5. Here's another simple I/O exercise. Write a C program called twoTokens.c that reads from standard input a line at a time. Assume no line is longer than 50 bytes. Copy to standard output all lines that contain exactly 2 tokens. See the man page for the scanf family of functions and look at sscanf. The trick here is to use fgets to read into a buffer and then use sscanf to read from the buffer. And recall that scanf() returns the number of conversions made - so try to read 3 tokens and see if it returns 2.
   
   The following might be a sample run:

   $ cat someLines
   
       two tokens
   but not here
   and              here
   1    2
     one    two
   one
     one two     three
   
           easy exercise
   $ twoTokens < someLines
       two tokens
   and              here
   1    2
     one    two
           easy exercise
   $