USH

Description

This program is a basic command-line interpreter with features without which there can be no shell. As a reference, i've taken zsh. During developing was implemented:

• default prompt looks like u$h> , followed by a space character

• builtin commands without flags:

  Command	Description
  export [name[=value] ...]	Set an environment variable with specified name
  unset name ...	Delete given shell variable.
  exit [n]	Exit the shell with the exit status specified by n expression, if none is specified, exit with 1 status.

• builtin commands with flags:

  Command	Description
  env	Set each NAME to VALUE in the environment and run COMMAND -i - start with an empty environment -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 - remove variable from the environment
  cd	Change current directory. -s - cd refuses to change the current directory if the given pathname contains symlinks -P - symbolic links are resolved to their true values -- - change to the previous directory
  pwd [-LP]	Print the absolute pathname of the current working directory -L - he default one -P - if -L flag is not given, the printed path will not contain symbolic
  which [-as] name	For each name, indicate how it would be interpreted if used as a command name. 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. -a - do a search for all occurrences of name throughout the command path. Normally only the first occurrence is printed. -s - if 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. -n - do not output the trailing newline -e - enable interpretation of backslash escapes -E - disable interpretation of backslash escapes (default)

• calling the builtin command instead of the binary program if there is a name match among them

• correct managing errors

• correct managing user environment

• running programs located in the directories listed in the PATH variable

• the command separator ;

• managing these expansions correctly:

  • 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

Some examples of working

How to start

This program was developed on the MacOS, so it works correctly there.

In folder with cloned project use make to compile project. Start program with ./ush.

To delete the program - make uninstall
To delete all 'obj' files - make clean
To reinstall the program - make reinstall