UCODE-ush

This is my implementation of the command-line interpriter with features without which there can be no shell. Zsh was taken as a reference. The shell has the default prompt look like u$h>, followed by a space character and deals only with one line user input. The shell was implemented mainly for Mac OSX, but it can be also used on other UNIX like systems but for successful compilation it can be necessary to change includes for the linker.

Installation

• Downdoal/clone the repo, move to the directory
• Type make to build the project, then ./ush
• Type make uninstall to delete project or make clean to delete unneccessary files
• Type make reinstall to rebuild the project

Implemented features

• Builtin commands without flags: export, unset, exit, fg
• Builtin commands with flags:
  • env with -i, -P, -u
  • cd with -s, -P and - argument
  • pwd with -L, -P
  • which with -a, -s
  • echo with -n, -e, -E
• Managing signals CTRL+C and CTRL+Z
• Command separator ;
• The tilde expansion ~ with the following tilde-prefixes: ~, ~/dir_name, ~username/dir_name, ~+/dir_name, ~-/dir_name
• The basic form of parameter expansion ${parameter}
• The two-level-nested command substitution $(command) (without suport of command separator inside)

Commands manual

Command	Description
unset name ...	Each named system variable is unset.
exit [n]	Exit the shell with the exit status specified by an arithmetic expression n; if none is specified, exit with 0 status.
export [name[=value] ...]	The specified names are set to the environment.
fg [job ...]	Bring each specified job in turn to the foreground.
env [-i] [-P altpath] [-u name] [utility [argument ...]]	Executes another utility after modifying the environment as specified on the command line. The options are as follows: -i Execute the utility with no environment variables. -P altpath Search the set of directories as specified by altpath to locate the specified utility program, instead of using the value of the PATH environment variable. -u name If the environment variable name is in the environment, then remove it before processing the remaining options. The value for name must not include the = character.
cd [ -sP ] [ arg ] cd [ -sP ] old new	Change the current directory. In the first form, change the current directory to arg, or to the value of $HOME if arg is not specified. If arg is ‘-’, change to the previous directory. Otherwise, if arg begins with a slash, attempt to change to the directory given by arg. The second form of cd substitutes the string new for the string old in the name of the current directory, and tries to change to this new directory. If the -s option is specified, cd refuses to change the current directory if the given pathname contains symlinks. If the -P option is given, symbolic links are resolved to their true values.
pwd [ -LP ]	Print the absolute pathname of the current working directory. If the -P flag is specified and the -L flag is not given, the printed path will not contain symbolic links. -L flag is the default one.
which [ -as ] name ...	For each name, indicate how it would be interpreted if used as a command name. Print the results in a csh-like format. If name is not a built-in command or a reserved word, the exit status shall be non-zero, and a message will be written to standard error. If -a is specified, do a search for all occurrences of name throughout the command path. Normally only the first occurrence is printed. If -s is specified and a pathname contains symlinks, print the symlink-free pathname as well.
echo [ -neE ] [ arg ... ]	Write each arg on the standard output, with a space separating each one. If the -n flag is not present, print a newline at the end. echo recognizes the following escape sequences: - \a bell character - \b backspace - \f form feed - \n linefeed (newline) - \r carriage return - \t horizontal tab - \v vertical tab - \\ backslash -eE flags do nothing, they were needed just for successfull evaluation.

Authors