Character Play

Last modified April 25, 2014

Background

Play

Take a look at the other functions available to you in the standard C library. Specifically look at stdio.h, focusing on “Character input/output” for now, and all functions defined in ctype.h.

Try looking at the man page for a few of the functions from the terminal, for example:
```
$ man isspace
```
The manual page is a valuable reference right at your finger tips. You can quickly look up what header files you will need to #include to use a particular function, what arguments a function takes and what it returns, as well as possible error considerations. From within the manual page viewer, press q to quit. I find it useful to keep a second window open that I can use to check the manual as I am writing code.
Try using some of the other functions available to you to make your program do some different character operations:
1. convert all characters to upper case
2. print only alphabetic characters
3. replace all non-alphabet characters with a new line character ‘\n’
4. capitalize the first letter of each word
Compile each program to a different name, for instance, you might call the program that replaces all non-alphabet characters with a new line split_words
```
$ clang -o split_words split_words.c
```
And try using your program in a pipeline with other programs you have written, for example
```
$ ./tolower | ./split_words
```
Try it with both input from the keyboard, and redirecting standard input to read from the a file
```
$ < /usr/share/data/jump.txt ./tolower | ./split_words
```
Note that the input redirect can come before or after the initial command:
```
$ ./tolower < /usr/share/data/jump.txt | ./split_words
```
will also work, but
```
$ ./tolower | ./split_words < /usr/share/data/jump.txt
```
will not produce the same behavior as the previous two examples. Why not?

Compile Errors

The clang compiler is a good example of a program that follows the “Silence is Golden” rule. If your compile your program and there are no errors, clang returns without printing anything to the terminal. The only change is you will have a new or updated executable file in your current directory. If your source contains errors then clang will print them to the terminal. If this happens, read the error message carefully. Refer to the referenced line and column number in your source code to find the spot the compiler had trouble with. If you don’t see any obvious syntax errors or typos, review the man page for the function that seems to be the source of the error. Between the error message clang provides and the contents of the manual pages, you should have all the information you need to fix the problem. If you aren’t sure how to interpret an error that clang gives you, ask a friend, ask the #ece2524 IRC channel, or ask me.

Deliverables

You do not need to submit any of your programs. Use them to experiment and learn how to use some of the functions in the standard library. The next quiz will contain questions that you should be able to answer after having worked through these exercises.