man_1_simple_shell

.\" Manpage for Shell

.TH dash 1 "24 March 2018" "1.0" "shell man page"

.SH NAME
    hsh - interface to the Unix system kernel

.SH SYNOPSIS
    $ [command] [-flags ]

.SH DESCRIPTION
     A Shell provides you with an interface to the system kernel.
     It gathers input from you and  executes  programs  based on
     that input. When a program  finishes executing, it displays
     that command's output followed by a new prompt.

.SH PROMPT
     The  prompt,  $,  which  is  called  the command prompt, is
     issued by the shell. While the prompt is displayed, you can
     type a command.
     Shell reads your input after you press Enter. It determines
     the command you want  executed by looking at the first word
     of  your  input. A  word  is  an unbroken set of characters.
     Spaces and tabs separate words.


.SH OPTIONS

Built-ins

     cd [arg]
     Change  the  current working directory. The shell parameter
     $HOME is the default if no directory is specified. If no
     directory arg is found and the  $CDPATH   parameter  contains
     a  list  of directories separated by colons, each of these
     directories is used as a prefix to arg in the given order,
     and the current directory is set to the first one that is found.
     $ cd /usf/lb

     env
     Prints the current environment

     exit [n]
     Causes the shell to exit with the exit status  specified by
     n. If n is omitted then the exit status is that of the last
     command executed. (An end of file will  also exit  from the
     shell).

Examples of Commands

     pwd
     Prints the name of the current directory. man pwd for more info

     ls
     Lists the files in the current working directory. man ls for more
     info.

     echo
     Displays a string to standard output. man echo for more info.

     sh
     A shell program written by Ken Thompson. man sh for more info.

.SH ENVIRONMENT

Examples of Environment Variables

     PATH
     A list of directories for executables.

     HOME
     The default home directory of the system

     USER
     The user of the current system

     PWD
     The current parent directory

.SH SEE ALSO
    sh(1),  csh(1),  environ(7),  execve(2), exit(3), getline(3),
    kill(2), malloc(3), perror(3), signal(2), strtok(3), wait(2),
    _exit(2), isatty(3).

.SH EXAMPLE CODE

From Main Function:


#define _GNU_SOURCE

#include <stdio.h>

#include "holberton.h"

int main(int ac, char **av, char **env)

{
        char *line, *newline;
        size_t len = 0;
        ssize_t characters;
        char **tokenarray;
        int cmdnum = 0;

        (void)ac, (void)av;
        while (1)
        {
                line = NULL;
                len = 0;
                cmdnum++;
                if (isatty(STDIN_FILENO) == 1)
                        printprompt();
                signal(SIGINT, ctrlc);
                characters = getline(&line, &len, stdin);
                if (characters == EOF || characters == -1)
                        return (ctrld(line));
                if (line[0] == '\n')
                {
                        free(line);
                        continue;
                }
		newline = _reallocchar(line);
                if (newline == NULL)
                {
                        free(line);
                        return (0);
                }
                tokenarray = tokensplit(newline);
                if (tokenarray == NULL)
                {
                        free(line);
                        free(newline);
                        return (0);
                }
                exec(tokenarray, env, av, line, newline, cmdnum);
                free_all(line, newline, tokenarray);
        }

}

.SH BUGS
     Not discovered yet

.SH AUTHORS
     Written by Derek Kwok and Elena Serebryakova