OS_Shell_Project

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Compile

make clean && make

Run

Interactive:

./shell

File input:

./shell < inputfile

Features

• Takes commands in the form of:

cmd [arg] * [|cmd [arg] * ] * [< fn1]? [ >[>]? fn2 ]? [ 2>fn3 || 2>&1 ] ?[&]?

• Piping, I/O redirection, Background processing
• Environment variables:
  • setenv, unsetenv, printenv
  • replacement with ${VARIABLE}
• Aliasing:
  • alias, unalias
  • alias with no arguments prints all aliases
  • checks for infinite aliases
  • catches excessively nested aliases
• Other builtin commands:
  • cd changes directory and updates PWD variable
  • bye allows you to exit the shell
    • SIGINT, SIGQUIT and SIGSTP are disabled in the shell process
  • All builtins can be forked, but running in a separate process negates some functionality. This is similar to implementation of other shells.
• Quotes:
  • Strings in quotes are taken literally
• Wildcard matching with * and ?
  • If no match is found, the pattern is used literally
• Errors:
  • Line numbers in non-interactive mode
  • Appropriate error messages
• Extra credit: tilde expansion
  • Tilde expansion occurs at the beginning of a word
  • Not implemented: tilde expansion within PATH variable

Not implemented

• File completion
• Tilde expansion in PATH variable