Homework 8: Dash-ing trough some tasks.

This homework is worth 15 points.

Goals

• Worked with fork, exec and wait
• Worked with dup

Assignment

• Execute a process. If the user enters a command other than a dash built-in, your shell should attempt to locate and execute the corresponding program.
  • Use the environment variable DASH_PATH which is a colon separated list of directories to locate executable with the given name.
  • For each directory named in DASH_PATH check to see if an executable file matching the command is given. If so execute that process.
  • DASH_PATH should provide the search order for your shell. The first directory listed should be searched first.
  • If a command is not found, print a corresponding error message.
  • Do not attempt to execute files with a matching name that are not executable for the user.
• Allow processes to be executed with command line arguments.
  • Any arguments not consumed by dash ( &, < file , > file) should be passed along to the process.
  • The current environment should be passed along to the process.
• Allow processes to be executed in the background
  • Under normal operation the shell should wait until the child exits before returning the prompt.
  • if the final argument is an & the process should be started and the shell should not wait.
  • The shell should keep a list of processes running in the background
• Add a dash build-in command TASKS which prints a list of background jobs.
  • This should include:
    • The process ID
    • The name of the command.
• Allow a process to redirect input and output.
  • If a command string contains <, the user would like the next argument (if it exists) to be used in place of standard in.
  • If a command string contains >, the user would like the next argument to be used in place of standard out.
  • If the redirect symbol is not followed by an additional argument, dash should print an error.

Submission