Your assignment is to write a C program that accepts as input another C program, specified on the command line (with argc and argv), and prints a nicely indented version of the input program on the standard output. "Nicely indented" for the purpose of this program means that statements within a compound statement are tabbed over one to the right of the statements above and below, for instance:

printf ("hello");
for (i=0; i<n; i++) {
	printf ("%d\n", i);
	scanf ("%d\n", &m);
	for (j=0; j<m; j++) {
		printf ("%d\n", j);
	}
}
printf ("goodbye");

Your program is required to:

• Handle arbitrary nesting of compound statements.
• Print statements with opening curly braces at the same level of indentation as the previous statements, as in the example above.
• Print statements with closing curly braces at the next level of indentation to the left, as in the example above.
• Warn the user on standard error (fprintf (stderr, ...)) if a program has unbalanced curly braces.
• Handle curly braces in comments (e.g. /* { */), single quotes (e.g. '{'), and double quotes (e.g. "{") correctly, i.e., take no action unless the curly brace is part of the program code and not part of a comment or quote.
• Warn the user on standard error (fprintf (stderr, ...)) if a program has unbalanced curly braces or quotes.
• Be able to work on itself as input, as well as any other reasonable C program.
• Exit with an appropriate error message and an error code of 1 if the wrong number of arguments is supplied on the command line or if the file can't be opened for reading.

• The basic idea is to read the program line by line with fgets(), and for each line, examining it character by character in a for loop. When you see a {, you know a compound statement is being started. When you see a }, you know a compound statement is being ended.
• See strip.c for a C program that strips the comments from a program named on the command line, writing the results to the standard output. This will give you a framework within which to write your program, and an idea of how to write a program-processing-program. The Standard C Library function perror used there prints the supplied argument, followed by a colon, followed by an error message indicating why the file could not be opened for input. Note that your program should not strip comments, simply ignore curly braces within them.
• Have an int variable called level that starts out at zero and represents the number of tabs to be printed before the current line. If a { occurs on the current line, increment level after printing the current line. If a } occurs on the current line, decrement level before printing the current line.
• Make sure to remove any whitespace (spaces or tabs) preceding the current line before printing your own tabs. Otherwise, any preexisting indentation in the program will be printed along with your indentation. You can do this using a for loop that examines the current string character by character until a non-whitespace character is found, then remembering that position and printing from there after doing your indentation. The C notation for a tab is '\t'.
• Have a variable called quoting that is true if and only if you are in the middle of a quote (single or double). If quoting is true, don't pay attention to any curly braces. quoting is set to true when it's false and you see a quote; it is set to false when it is true and you see a quote.
• Your program does not need to be too smart about C; it just needs to know about curly braces, comments, and quotes. Don't worry about indenting if/else statements without compound statements. Don't worry about syntax errors in the program to be processed; your program is not a C compiler, just an indenting program.
• Don't worry about comments within quotes, that's getting a bit silly.
• The instructor's program is not named indent for a reason: the name indent is an existing Unix program with a similar purpose. If you name your program indent, chances are you will be executing the other indent by mistake.

Turn in your program by e-mailing the C source (indented and commented nicely!) to the instructor. Remember to post your progress report discussing this program et cetera to the newsgroup by the due date.

This assignment is due at midnight on Monday, July 21, 1997.