A little command shell

• prints a prompt,
• gets a command line from the user,
• searches the $PATH environment variable for a program whose name is the first word in the command string, and forks a child process to execute the first such program found, passing the command-line arguments (including the program name itself) to the program (or printing an error message if no command is found),
• waits for the execution to finish,
• prints out a line reporting the exit value of the command being executed, and
• goes back to the first step.

Your shell should also trap CTL-C's--upon receiving a SIGINT, it should tell the user to type CTL-] followed by <return> to quit your shell.

Work in groups of 2 or 3. No solo programs, please.

Here are a few technical points that may interest you:

• Typing CTL-] sends a character with ASCII value 29. This character, known as "GS" or "Group Separator," goes along with "FS" (28, CTL-\, "File Separator"), "RS" (30, CTL-^, "Record Separator"), and "US" (31, CTL-_, "Unit Separator"). The ASCII standard says "These information separators may be used with data in optional fashion, except that their hierarchical relationship shall be: FS as the most inclusive, then GS, then RS, and US as least inclusive [is this a political statement?]. The content and length of a file, group, record, or unit are not specified." So in other words, nobody uses these characters anymore, except when they need a character that nobody uses anymore.
• "man execl" will get you a start on using exec. The "l" in "execl" stands for "list," which means that when you call execl(), you give it a list of command-line argument strings. The "p" in "execlp" stands for "path," which means that "execlp" looks for the file-to-be-executed in all the directories specified in your PATH environment variable. To see what your PATH is, type "echo $PATH" at the Unix prompt. If you want to look all over the place for the file-to-be-executed, use execlp(). If you only want to look in the current directory, use execl(). You might also wish to consider using execv() or execvp().