Initial Commit
This commit is contained in:
hellisabove
@@ -0,0 +1,249 @@
|
||||
// C Program to design a shell in Linux
|
||||
#include<stdio.h>
|
||||
#include<string.h>
|
||||
#include<stdlib.h>
|
||||
#include<unistd.h>
|
||||
#include<sys/types.h>
|
||||
#include<sys/wait.h>
|
||||
#include<readline/readline.h>
|
||||
#include<readline/history.h>
|
||||
|
||||
#define MAXCOM 1000 // max number of letters to be supported
|
||||
#define MAXLIST 100 // max number of commands to be supported
|
||||
|
||||
// Clearing the shell using escape sequences
|
||||
#define clear() printf("\033[H\033[J")
|
||||
|
||||
// Function to take input
|
||||
int takeInput(char* str)
|
||||
{
|
||||
char* buf;
|
||||
|
||||
buf = readline("\n$ ");
|
||||
if (strlen(buf) != 0) {
|
||||
add_history(buf);
|
||||
strcpy(str, buf);
|
||||
return 0;
|
||||
} else {
|
||||
return 1;
|
||||
}
|
||||
}
|
||||
|
||||
// Function where the system command is executed
|
||||
void execArgs(char** parsed)
|
||||
{
|
||||
// Forking a child
|
||||
pid_t pid = fork();
|
||||
|
||||
if (pid == -1) {
|
||||
printf("\nFailed forking child..");
|
||||
return;
|
||||
} else if (pid == 0) {
|
||||
if (execvp(parsed[0], parsed) < 0) {
|
||||
printf("\nCould not execute command..");
|
||||
}
|
||||
exit(0);
|
||||
} else {
|
||||
// waiting for child to terminate
|
||||
wait(NULL);
|
||||
return;
|
||||
}
|
||||
}
|
||||
|
||||
// Function where the piped system commands is executed
|
||||
void execArgsPiped(char** parsed, char** parsedpipe)
|
||||
{
|
||||
// 0 is read end, 1 is write end
|
||||
int pipefd[2];
|
||||
pid_t p1, p2;
|
||||
|
||||
if (pipe(pipefd) < 0) {
|
||||
printf("\nPipe could not be initialized");
|
||||
return;
|
||||
}
|
||||
p1 = fork();
|
||||
if (p1 < 0) {
|
||||
printf("\nCould not fork");
|
||||
return;
|
||||
}
|
||||
|
||||
if (p1 == 0) {
|
||||
// Child 1 executing..
|
||||
// It only needs to write at the write end
|
||||
close(pipefd[0]);
|
||||
dup2(pipefd[1], STDOUT_FILENO);
|
||||
close(pipefd[1]);
|
||||
|
||||
if (execvp(parsed[0], parsed) < 0) {
|
||||
printf("\nCould not execute command 1..");
|
||||
exit(0);
|
||||
}
|
||||
} else {
|
||||
// Parent executing
|
||||
p2 = fork();
|
||||
|
||||
if (p2 < 0) {
|
||||
printf("\nCould not fork");
|
||||
return;
|
||||
}
|
||||
|
||||
// Child 2 executing..
|
||||
// It only needs to read at the read end
|
||||
if (p2 == 0) {
|
||||
close(pipefd[1]);
|
||||
dup2(pipefd[0], STDIN_FILENO);
|
||||
close(pipefd[0]);
|
||||
if (execvp(parsedpipe[0], parsedpipe) < 0) {
|
||||
printf("\nCould not execute command 2..");
|
||||
exit(0);
|
||||
}
|
||||
} else {
|
||||
// parent executing, waiting for two children
|
||||
wait(NULL);
|
||||
wait(NULL);
|
||||
}
|
||||
}
|
||||
}
|
||||
|
||||
// Help command builtin
|
||||
void openHelp()
|
||||
{
|
||||
puts("\n***WELCOME TO MY SHELL HELP***"
|
||||
"\nCopyright @ Suprotik Dey"
|
||||
"\n-Use the shell at your own risk..."
|
||||
"\nList of Commands supported:"
|
||||
"\n>cd"
|
||||
"\n>ls"
|
||||
"\n>exit"
|
||||
"\n>all other general commands available in UNIX shell"
|
||||
"\n>pipe handling"
|
||||
"\n>improper space handling");
|
||||
|
||||
return;
|
||||
}
|
||||
|
||||
// Function to execute builtin commands
|
||||
int ownCmdHandler(char** parsed)
|
||||
{
|
||||
int NoOfOwnCmds = 4, i, switchOwnArg = 0;
|
||||
char* ListOfOwnCmds[NoOfOwnCmds];
|
||||
char* username;
|
||||
|
||||
ListOfOwnCmds[0] = "exit";
|
||||
ListOfOwnCmds[1] = "cd";
|
||||
ListOfOwnCmds[2] = "help";
|
||||
ListOfOwnCmds[3] = "hello";
|
||||
|
||||
for (i = 0; i < NoOfOwnCmds; i++) {
|
||||
if (strcmp(parsed[0], ListOfOwnCmds[i]) == 0) {
|
||||
switchOwnArg = i + 1;
|
||||
break;
|
||||
}
|
||||
}
|
||||
|
||||
switch (switchOwnArg) {
|
||||
case 1:
|
||||
exit(0);
|
||||
case 2:
|
||||
chdir(parsed[1]);
|
||||
return 1;
|
||||
case 3:
|
||||
openHelp();
|
||||
return 1;
|
||||
case 4:
|
||||
username = getenv("USER");
|
||||
printf("\nHello %s.\nMind that this is "
|
||||
"not a place to play around."
|
||||
"\nUse help to know more..\n",
|
||||
username);
|
||||
return 1;
|
||||
default:
|
||||
break;
|
||||
}
|
||||
|
||||
return 0;
|
||||
}
|
||||
|
||||
// function for finding pipe
|
||||
int parsePipe(char* str, char** strpiped)
|
||||
{
|
||||
int i;
|
||||
for (i = 0; i < 2; i++) {
|
||||
strpiped[i] = strsep(&str, "|");
|
||||
if (strpiped[i] == NULL)
|
||||
break;
|
||||
}
|
||||
|
||||
if (strpiped[1] == NULL)
|
||||
return 0; // returns zero if no pipe is found.
|
||||
else {
|
||||
return 1;
|
||||
}
|
||||
}
|
||||
|
||||
// function for parsing command words
|
||||
void parseSpace(char* str, char** parsed)
|
||||
{
|
||||
int i;
|
||||
|
||||
for (i = 0; i < MAXLIST; i++) {
|
||||
parsed[i] = strsep(&str, " ");
|
||||
|
||||
if (parsed[i] == NULL)
|
||||
break;
|
||||
if (strlen(parsed[i]) == 0)
|
||||
i--;
|
||||
}
|
||||
}
|
||||
|
||||
int processString(char* str, char** parsed, char** parsedpipe)
|
||||
{
|
||||
|
||||
char* strpiped[2];
|
||||
int piped = 0;
|
||||
|
||||
piped = parsePipe(str, strpiped);
|
||||
|
||||
if (piped) {
|
||||
parseSpace(strpiped[0], parsed);
|
||||
parseSpace(strpiped[1], parsedpipe);
|
||||
|
||||
} else {
|
||||
|
||||
parseSpace(str, parsed);
|
||||
}
|
||||
|
||||
if (ownCmdHandler(parsed))
|
||||
return 0;
|
||||
else
|
||||
return 1 + piped;
|
||||
}
|
||||
|
||||
int main()
|
||||
{
|
||||
char inputString[MAXCOM], *parsedArgs[MAXLIST];
|
||||
char* parsedArgsPiped[MAXLIST];
|
||||
int execFlag = 0;
|
||||
|
||||
while (1) {
|
||||
// take input
|
||||
if (takeInput(inputString))
|
||||
continue;
|
||||
// process
|
||||
execFlag = processString(inputString,
|
||||
parsedArgs, parsedArgsPiped);
|
||||
// execflag returns zero if there is no command
|
||||
// or it is a builtin command,
|
||||
// 1 if it is a simple command
|
||||
// 2 if it is including a pipe.
|
||||
|
||||
// execute
|
||||
if (execFlag == 1)
|
||||
execArgs(parsedArgs);
|
||||
|
||||
if (execFlag == 2)
|
||||
execArgsPiped(parsedArgs, parsedArgsPiped);
|
||||
}
|
||||
return 0;
|
||||
}
|
||||
|
||||
Reference in New Issue
Block a user