To compile ./smallsh , run make all or simply make.
In this assignment you will write smallsh your own shell in C. smallsh will implement a subset of features of well-known shells, such as bash. Your program will
- Provide a prompt for running commands
- Handle blank lines and comments, which are lines beginning with the
#character - Provide expansion for the variable
$$ - Execute 3 commands exit, cd, and status via code built into the shell
- Execute other commands by creating new processes using a function from the exec family of functions
- Support input and output redirection
- Support running commands in foreground and background processes
- Automatically redirect stdin and stdout to /dev/null
- Implement custom handlers for 2 signals, SIGINT and SIGTSTP
The general syntax of a command line is:
command [arg1 arg2 ...] [< input_file] [> output_file] [&]
...where items in square brackets are optional.
- You can assume that a command is made up of words separated by spaces.
- The special symbols <, > and & are recognized, but they must be surrounded by spaces like other words.
- If the command is to be executed in the background, the last word must be &. If the & character appears anywhere else, just treat it as normal text.
- If standard input or output is to be redirected, the > or < words followed by a filename word must appear after all the arguments. Input redirection can appear before or after output redirection.
- Your shell does not need to support any quoting; so arguments with spaces inside them are not possible. We are also not implementing the pipe "|" operator.
- Your shell must support command lines with a maximum length of 2048 characters, and a maximum of 512 arguments.
- You do not need to do any error checking on the syntax of the command line.