added more code

CPE435/Lab3/a.txt

@@ -0,0 +1,26 @@
+total 1.2M
+drwx------ 2 anw0044 student 4.0K Feb  8 20:59 .
+drwx------ 7 anw0044 student 4.0K Feb  1 16:17 ..
+-rw------- 1 anw0044 student    0 Feb  8 21:00 a.txt
+-rw------- 1 anw0044 student  189 Feb  8 20:17 a.txt
+
+-rwx------ 1 anw0044 student 8.3K Feb  6 21:55 demo1
+-rw------- 1 anw0044 student 1.6K Feb  7 19:31 demo1.c
+-rwx------ 1 anw0044 student 9.8K Feb  8 09:12 demo2
+-rw------- 1 anw0044 student 1.3K Feb  8 09:12 demo2.c
+-rwx------ 1 anw0044 student 8.6K Feb  6 21:56 demo3
+-rw------- 1 anw0044 student 1.7K Feb  7 19:31 demo3.c
+-rwx------ 1 anw0044 student 8.4K Feb  7 01:09 demo4
+-rw------- 1 anw0044 student 1.7K Feb  8 01:15 demo4.c
+-rwx------ 1 anw0044 student 8.5K Feb  6 21:56 demo5
+-rw------- 1 anw0044 student 1.3K Feb  7 19:31 demo5.c
+-rwx------ 1 anw0044 student 8.4K Feb  8 02:17 example2
+-rw------- 1 anw0044 student  271 Jan 27 16:19 example2.c
+-rwx------ 1 anw0044 student 8.5K Feb  8 02:17 example3
+-rw------- 1 anw0044 student  536 Jan 27 16:19 example3.c
+-rw------- 1 anw0044 student 121K Jan 27 16:19 Lab03.pdf
+-rwx------ 1 anw0044 student  17K Feb  8 20:59 shell
+-rw------- 1 anw0044 student 7.4K Feb  8 20:58 shell.c
+-rw------- 1 anw0044 student 417K Jan 27 16:19 Study_Lab03.pdf
+-rw------- 1 anw0044 student 482K Jan 27 16:19 Study_Lab03.pptx
+-rw------- 1 anw0044 student   94 Feb  8 09:12 test.txt

CPE435/Lab3/demo1.c

@@ -0,0 +1,44 @@
+/*
+Written By: Prawar Poudel 
+This program is intended to showcase the use of strtok() function 
+Please study about the strtok function first and compare the three outputs that you will receive here 
+*/ 
+#include <stdio.h> 
+#include <stdlib.h> 
+#include <string.h> 
+int main(int argc,char* argv[]) 
+{ 
+	printf("Demo Number 1\n"); 
+	printf("================\n"); 
+	char myString[100] = "i,want to break,this string using, both,comma and space"; 
+	//following is the temporary string that I want to keep my char[] read from breaking the above char[] myString 
+	//following breaks based on space character 
+	char *temp; 
+	temp = strtok(myString," "); //include <space> inside "" 
+	while(temp!=NULL) 
+	{ 
+		printf("%s\n",temp); 
+		temp = strtok(NULL," "); //include <space> inside "" 
+	} 
+	//following breaks based on comma character 
+	printf("\n\nDemo Number 2\n"); 
+	printf("================\n"); 
+	strcpy(myString,"i,want to break,this string using, both,comma and space"); 
+	temp = strtok(myString,","); //include , inside "" 
+	while(temp!=NULL) 
+	{ 
+		printf("%s\n",temp); 
+		temp = strtok(NULL,","); //include , inside "" 
+	} 
+	//following breaks based on space or comma character 
+	printf("\n\nDemo Number 3\n"); 
+	printf("================\n"); 
+	strcpy(myString,"i,want to break,this string using, both,comma and space");
+	temp = strtok(myString,", "); //include both space and , inside "" while(temp!=NULL) 
+	while(temp!=NULL) 
+	{ 
+		printf("%s\n",temp); 
+		temp = strtok(NULL,", "); //include both space and , inside "" 
+	} 
+	return 0; 
+}

CPE435/Lab3/demo2.c

@@ -0,0 +1,33 @@
+/* 
+Written By: Prawar Poudel 
+This program is supposed to demonstrate the execution of dup2() function 
+Please read the manual page first before jumping to run this program 
+*/ 
+#include <stdio.h> 
+#include <unistd.h> 
+#include <sys/wait.h> 
+#include <stdlib.h> 
+#include <fcntl.h> 
+int main() 
+{ 
+	printf("You would expect this to go to your stdout, and it does\n"); 
+	//we will create a file using open function 
+	char myFileName[] = "test.txt"; 
+	//lets open the file by the name of test.txt 
+	int myDescriptor = open(myFileName,O_CREAT|O_RDWR|O_TRUNC,0644); 
+	int id; 
+	//creating a child that redirects the stdout to test.txt 
+	// you can use similar functionality for '>' operator 
+	if((id=fork())==0) 
+	{ 
+		//lets call dup2 so that out stdout (second argument) is now copied to (points to) test.txt (first argument) 
+		// what this essentially means is that anything that you send to stdout will be sent to myDescriptor 
+		dup2(myDescriptor,1); //1 is stdout, 0 is stdin and 2 is stderr 
+		printf("You would expect this to go to your stdout, but since we called dup2, this will go to test.txt"); 
+		close(myDescriptor); 
+		exit(0);
+	}else 
+		wait(0); 
+	printf("This is also printed to the console\n"); 
+	return 0; 
+} 

CPE435/Lab3/demo3.c

@@ -0,0 +1,49 @@
+/* 
+Written By: Prawar Poudel
+This program demonstrates the use of pipe() function in C 
+Please man pipe and have understanding before going through this code 
+Pipe passes information from one process to another, similar to water-pipes there is a read-end and a write-end of pipe 
+*/ 
+#include <stdio.h> 
+#include <unistd.h> 
+#include <stdlib.h> 
+#include <fcntl.h> 
+#include <sys/wait.h> 
+int main() 
+{ 
+	int myPipingDescriptors[2]; 
+	if(pipe(myPipingDescriptors)==-1) 
+	{ 
+		printf("Error in calling the piping function\n"); 
+		exit(0); 
+	} 
+	//at this point two pipe ends are created 
+	// one is the read end and other is write end 
+	// [0] will be the read end, [1] will be the write end 
+	//now lets fork two process where one will make use of the read end and other will make 
+	// use of write end 
+	// they can communicate this way through the pipe 
+	int id; 
+	if((id=fork())==0) 
+	{ 
+		dup2(myPipingDescriptors[1],1); //second argument 1 is stdout 
+		close(myPipingDescriptors[0]); //read end is unused to lets close it 
+		//this following statement will not be printed since we have copied the stdout to write end of pipe 
+		printf("I am child, and sending this message.\n"); 
+		exit(0); 
+	}else if (id>0) 
+	{ 
+		wait(0); 
+		char myRead[100]; 
+		//basically what's written to the write-end of pipe stays there until we read the read-end of pipe 
+		read(myPipingDescriptors[0],myRead,37); 
+		printf("I am parent. I read following statement\n\t%s\n",myRead); close(myPipingDescriptors[1]); 
+	}else 
+	{
+		printf("Failed to fork so terminating the process\n"); 
+		exit(-1); 
+	} 
+	close(myPipingDescriptors[0]); 
+	close(myPipingDescriptors[1]); 
+	return 0; 
+} 

CPE435/Lab3/demo4.c

@@ -0,0 +1,46 @@
+/* 
+Written By: Prawar Poudel 
+execvp runs a program that you pass as argument 
+Please study about the execvp function before going to run this program 
+After you understand the things, please run and watch them 
+Please make sure that execvp has the right executable provided 
+*/ 
+#include <unistd.h> 
+#include <string.h> 
+#include <stdio.h> 
+#include <sys/wait.h> 
+int main() 
+{ 
+	char myArgument[100]; 
+	//you can change the content of myArgument using any user typed input using gets() 
+	strcpy(myArgument,"date"); 
+	//execvp expects the arguments to be provided as char[][] 
+	//so please make sure you understand strtok before coming here 
+	//we will use strtok() to break the sequence of command and argument in myArgument to convert to char[][] 
+	char* myBrokenArgs[10]; //this will hold the values after we tokenize 
+	printf("Starting tokenization...\n");
+	myBrokenArgs[0] = strtok(myArgument," "); 
+	int counter = 0; 
+	while(myBrokenArgs[counter]!=NULL) 
+	{ 
+		counter+=1; 
+		myBrokenArgs[counter] = strtok(NULL," "); 
+	} 
+	myBrokenArgs[counter] = NULL; 
+	printf("\ttokenization complete....\n\nNow executing using execvp\n"); 
+	printf("Following will be the output of execvp\n"); 
+	printf("=======================================\n"); 
+	int id;
+	//I will spawn a child that will run my execvp command 
+	if((id=fork())==0)
+			execvp(myBrokenArgs[0],myBrokenArgs);
+	else if(id<0)
+			printf("Failed to make child...\n");
+	else
+	{
+		//parent shall wait until the child is killed
+		wait(0); 
+		printf("=======================================\n"); printf("Completed execution\n"); 
+	} 
+	return 0; 
+}

CPE435/Lab3/demo5.c

@@ -0,0 +1,57 @@
+/*
+	program runs "ls | sort" command using 2 child processes
+	
+	dup2 is used to duplicate an old file descriptor into a new one
+	normal file descriptor table
+	
+		0 [ standard input  ]
+		1 [ standard output ]
+		2 [ standard error  ]	
+
+	pipe is used to communicate between child processes
+	unused ends of the pipe should be closed if unused
+	in that process
+
+
+
+*/
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+int main()
+{
+	int fds[2];
+	pipe(fds);
+	// Child 1 will duplicate downstream into stdin
+	if(fork() == 0)
+	{
+		dup2(fds[0], 0); // normally 0 is for stdin
+				 // will now read to fds[0]
+				 // end of pipe 
+		close(fds[1]);   // close other end of pipe
+		execlp("sort", "sort", 0);
+		//execlp("wc", "wc", "-l", 0); // Note the first argument is the command
+					       // After it are the arguments including
+					       // original command
+	}
+	// Child2 duplicates upstream into stdout
+	else if (fork() == 0)
+	{
+		dup2(fds[1], 1); // normally 1 is for stdout
+				 // will now write to fds[1] 
+				 // end of pipe
+		close(fds[0]);   // close other end of pipe
+		execlp("ls", "ls", 0);
+	}
+	// Parent
+	else
+	{
+		close(fds[0]);
+		close(fds[1]);
+		wait(0);
+		wait(0);
+	}
+}

CPE435/Lab3/example2.c

@@ -0,0 +1,14 @@
+#include <unistd.h>
+#include <string.h>
+#include <stdio.h>
+#include <sys/wait.h>
+
+int main()
+{
+	char *cmd[] = {"who", "ls", "date"};
+	int i;
+	printf("0=who, 1=ls, 2=date :");
+	scanf("%d", &i);
+	execlp(cmd[i], cmd[i], 0);
+	printf("command not found\n"); /*exec failed*/
+}

CPE435/Lab3/example3.c

@@ -0,0 +1,28 @@
+#include <unistd.h>
+#include <string.h>
+#include <stdio.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+
+int main()
+{
+	char *cmd[] = {"who", "ls", "date", "notacommand"};
+	int i;
+	while(1)
+	{
+		printf("0=who, 1=ls, 2=date, 3=notacommand :");
+		scanf("%d", &i);
+		if(fork() == 0)
+		{
+			execlp(cmd[i], cmd[i], 0);	// If execlp runs correctly, control 
+							// is transfer to the new program
+			printf("command not found\n");  // exec failed
+			exit(1);
+		}
+		else
+		{
+			// Parent waits for child process to complete
+			wait(0);
+		}
+	}
+}

CPE435/Lab3/shell.c

@@ -0,0 +1,278 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+#include <stdlib.h>
+#include <fcntl.h> 
+#include <string.h>
+#include <sys/wait.h>
+
+char* substr(const char *src, int m, int n);
+void pipeFunc(char *command1, char *command2);
+
+int main() 
+{
+	while (1)
+	{
+		printf("My Shell\n"); 
+		printf(">> ");
+		//following is the temporary string that I want to keep my char[] read from breaking the above char[] myString 
+		//following breaks based on space character
+		char commandStr[100], commandStrFull[100];
+		char *temp;
+		char *temp2;
+		char temp3[100];
+		//strcpy(commandStr, "exit");
+		fgets(commandStr, 100, stdin);
+		//strcpy(commandStr, "ls -l > a.txt");
+		strcpy(commandStrFull,commandStr);
+		char *filename;
+		int flag = 0;
+		// exit program if command is exit
+		if(strcmp(commandStr, "exit\n")==0)
+		{
+			exit(-1);
+		}
+
+		int redir=0;
+		int redirIndex;
+		int pipeNum=0;
+		int single=0;
+		char* redirCheckTwo=NULL;
+		char* command2;
+		char* command1;
+		char* pipeCheck = strchr(commandStr, '|');
+		char* redirCheck = strchr(commandStr, '>');
+		if(pipeCheck!=NULL)
+		{
+			pipeNum=1;
+			redirCheckTwo = strchr(commandStr, '>');
+			command1 = strrchr(commandStr, '|');
+			redirIndex = strcspn(commandStr, ">");
+		}
+		else single=1;
+		if (redirCheckTwo!=NULL)
+		{
+			command1 = strrchr(commandStr, '|');
+			redir=1;
+		}
+		if(redirCheck!=NULL) redir=1;
+		//commandStr[strcspn(commandStr, "\n")] = 0;
+		// pipe or redirect
+		if (pipeNum==1 || redir==1)
+		{
+			temp = strtok(commandStr," "); //include , inside "" 
+			while(temp!=NULL) 
+			{ 
+				//printf("%s\n",temp);
+				if (strcmp(temp,">")==0 && redir==1)
+				{
+					filename = strtok(NULL, " ");
+					//printf("Filename: %s\n", filename);
+				}
+				if (strcmp(temp,"|")==0 && pipeCheck!=NULL)
+				{
+					command2 = strtok(NULL," >");
+					//puts(strchr(temp, '|'));
+					flag=1;
+				}
+				
+				if (pipeNum==1 || redir==1)
+				{
+					temp = strtok(NULL," "); //include , inside ""
+				}
+				else temp2 = strtok(NULL," "); //include , inside ""
+			}
+		}
+		// single command is run
+		if(single==1 && pipeNum==0 && redir==0){
+			commandStr[strcspn(commandStr, "\n")] = 0;
+			//strcpy(temp,commandStr);
+
+			//execvp expects the arguments to be provided as char[][] 
+			//so please make sure you understand strtok before coming here 
+			//we will use strtok() to break the sequence of command and argument in myArgument to convert to char[][] 
+			char* myBrokenArgs[10]; //this will hold the values after we tokenize
+			//printf("Starting tokenization...\n");
+			myBrokenArgs[0] = strtok(commandStr," ");
+			int counter = 0; 
+			while(myBrokenArgs[counter]!=NULL)
+			{
+				counter+=1;
+				myBrokenArgs[counter] = strtok(NULL," ");
+			}
+			myBrokenArgs[counter] = NULL;
+			//printf("\ttokenization complete....\n\nNow executing using execvp\n"); 
+			//printf("Following will be the output of execvp\n");
+			//printf("=======================================\n");
+			if ((strcmp("ls",myBrokenArgs[0]) ==0) && single==1)
+			{
+				int id;
+				//I will spawn a child that will run my execvp command 
+				if((id=fork())==0)
+						execvp(myBrokenArgs[0],myBrokenArgs);
+				else if(id<0)
+						printf("Failed to make child...\n");
+				else
+				{ 
+					//parent shall wait until the child is killed
+					wait(0); 
+					printf("=======================================\n");
+					printf("Completed execution\n"); 
+				}
+			}
+			else if (strcmp("date",myBrokenArgs[0]) ==0)
+			{
+				int id;
+				//I will spawn a child that will run my execvp command 
+				if((id=fork())==0)
+						execvp(myBrokenArgs[0],myBrokenArgs);
+				else if(id<0)
+						printf("Failed to make child...\n");
+				else
+				{ 
+					//parent shall wait until the child is killed
+					wait(0); 
+					printf("=======================================\n");
+					printf("Completed execution\n"); 
+				}
+			}
+			else if ((strcmp("ps",myBrokenArgs[0]) ==0))
+			{
+				int id;
+				//I will spawn a child that will run my execvp command 
+				if((id=fork())==0)
+						execvp(myBrokenArgs[0],myBrokenArgs);
+				else if(id<0)
+						printf("Failed to make child...\n");
+				else
+				{ 
+					//parent shall wait until the child is killed
+					wait(0); 
+					printf("=======================================\n");
+					printf("Completed execution\n"); 
+				}
+			}
+		}
+		// pipe is used
+		if (pipeNum==1 && redirCheck==NULL && single==0)
+		{
+			strcpy(commandStrFull, "ls -lah | wc -l");
+			int size = strcspn(commandStrFull, "|");
+			int end = strcspn(commandStrFull, "\0");
+			int beg = strcspn(commandStrFull, "|");
+			char* command2 = substr(commandStrFull, beg+2, end);
+
+			end = strcspn(commandStrFull, "|");
+			char* command1 = substr(commandStrFull, 0, end-1);
+
+			char* command1Args[10]; //this will hold the values after we tokenize
+			//printf("Starting tokenization...\n");
+			command1Args[0] = strtok(command1," ");
+			int counter = 0; 
+			while(command1Args[counter]!=NULL)
+			{
+				counter+=1;
+				command1Args[counter] = strtok(NULL,"\0");
+			}
+			command1Args[counter] = NULL;
+
+			char* command2Args[10]; //this will hold the values after we tokenize
+			//printf("Starting tokenization...\n");
+			command2Args[0] = strtok(command2," ");
+			counter = 0;
+			while(command2Args[counter]!=NULL)
+			{
+				counter+=1;
+				command2Args[counter] = strtok(NULL," ");
+			}
+			command2Args[counter] = NULL;
+
+			int fds[2];
+			pipe(fds);
+			// Child 1 will duplicate downstream into stdin
+			if(fork() == 0)
+			{
+				dup2(fds[0], 0); // normally 0 is for stdin
+						// will now read to fds[0]
+						// end of pipe 
+				close(fds[1]);   // close other end of pipe
+				execlp(command2Args[0] ,command2Args[0], command2Args, 0);
+				//execlp("wc", "wc", "-l", 0); // Note the first argument is the command
+								// After it are the arguments including
+								// original command
+			}
+			// Child2 duplicates upstream into stdout
+			else if (fork() == 0)
+			{
+				dup2(fds[1], 1); // normally 1 is for stdout
+						// will now write to fds[1] 
+						// end of pipe
+				close(fds[0]);   // close other end of pipe
+				execlp(command1Args[0],command1Args[0], command1Args, 0);
+			}
+			// Parent
+			else
+			{
+				close(fds[0]);
+				close(fds[1]);
+				wait(0);
+				wait(0);
+			}
+		}
+		if (pipeNum==0 && redir==1)
+		{
+			int end = strcspn(commandStrFull, ">");
+			int beg = strcspn(commandStrFull, "|");
+			char* command1 = substr(commandStrFull, 0, end-1);
+			char* myBrokenArgs[10]; //this will hold the values after we tokenize
+			printf("Starting tokenization...\n");
+			myBrokenArgs[0] = strtok(command1," ");
+			int counter = 0; 
+			while(myBrokenArgs[counter]!=NULL)
+			{
+				counter+=1;
+				myBrokenArgs[counter] = strtok(NULL," ");
+			}
+			myBrokenArgs[counter] = NULL;
+
+			int myDescriptor = open(filename,O_CREAT|O_RDWR|O_TRUNC,0644); 
+			int id; 
+			//creating a child that redirects the stdout to test.txt 
+			// you can use similar functionality for '>' operator 
+			if((id=fork())==0) 
+			{ 
+				//lets call dup2 so that out stdout (second argument) is now copied to (points to) test.txt (first argument) 
+				// what this essentially means is that anything that you send to stdout will be sent to myDescriptor 
+				dup2(myDescriptor,1); //1 is stdout, 0 is stdin and 2 is stderr 
+				execvp(myBrokenArgs[0],myBrokenArgs);
+				close(myDescriptor); 
+				exit(0);
+			}else 
+				wait(0); 
+			printf("Completed execution.\n");
+		}
+	}	 
+		return 0;
+	
+}
+
+void pipeFunc(char *command1, char *command2)
+{
+	
+}
+
+char* substr(const char *src, int m, int n)
+{
+    // get the length of the destination string
+    int len = n - m;
+ 
+    // allocate (len + 1) chars for destination (+1 for extra null character)
+    char *dest = (char*)malloc(sizeof(char) * (len + 1));
+ 
+    // start with m'th char and copy `len` chars into the destination
+    strncpy(dest, (src + m), len);
+ 
+    // return the destination string
+    return dest;
+}

CPE435/Lab3/test.txt

@@ -0,0 +1 @@
+You would expect this to go to your stdout, but since we called dup2, this will go to test.txt