Basic Built-In Shell Functions/Features

[Glavin001]

• [x] Show the current working directory in shell prompt
  • http://stackoverflow.com/a/298518/2578205
  • Environment variables in general: http://www.gnu.org/software/libc/manual/html_node/Environment-Access.html#Environment-Access
• [x] Show username in shell prompt
  • http://www.unix.com/81721-post4.html (from http://www.unix.com/programming/21041-getting-username-c-program-unix.html)
• [x] cd
  • http://stackoverflow.com/a/9859965/2578205
  • http://linux.die.net/man/2/chdir
• [x] Basic redirection with |
• [x] File redirection support, >>, >
• [x] Backslash escaping characters
  • For instance, a\ b should be a single string a b and not two a and b
• [x] ~ support for $HOME in path args

[Glavin001]

See http://stackoverflow.com/a/11958481/2578205 for obtaining the current Git branch.

@Frozenfire92 's dotfiles: https://github.com/Frozenfire92/dotfiles/blob/master/.bash_profile

[Glavin001]

Quick brief of how I'd do it, for anyone interested, before I go pass out: 1) Iterate linearly thru all command line args (argv[0], argv[1], argv[2]). Let's deal with argv[0] from here on, the first arg. 2) Any time where the first character (argv[0][0]) is equal to the char "~" then continue with step 3 3) use malloc to allocate a char array with the size of $HOME plus the original argv[0] length minus 1 (for the ~ that is removed in argv[0]). This will be the new length of that argv[0]. 4) Starting from the beginning, fill the char array with the chars in $HOME 5) Next, starting at the end where $HOME left off, in the new char array, continue with the original contents of the char array in argv[0], starting at argv[0][1](skipping argv[0][0] which is the ~ to be removed). You have now filled the contents of the char array with the resolved path. Your new char array for the argv[0] is now stored in your new char array. Switch the pointers of argv[0] to the new array and dealloc the old argv[0]. Apply this function to every argument, in either the parse or execute function. This will allow us to support:

• path executables (~/Projects/MrShell/builds/mrsh)
• path arguments (cd ~/Projects/MrShell) Note: Remember that backslash should escape characters, such as ~ or spaces. This will be implicitly handled because we directly check only argv[0][0](the first char of the current arg) against '~'. If it was escaped by a backslash it would be a \ in the first position.

[Glavin001]

All done!