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#include <stdio.h>
#include <signal.h>
#include <sys/types.h>
#include <ctype.h>
//This method looks up the input command against the lookup for
//validity purposes
bool FunctionLookUp(char *argv, char *Lookup[])
{
bool match = false;
for(int i = 0; i < 10; i++){
if(*Lookup[i] == *argv){
match = true;
break;}
}
return match;
}
void parse(char *line, char **argv)
{
while (*line != '\0') { /* if not the end of line ....... */
while (*line == ' ' || *line == '\t' || *line == '\n')
*line++ = '\0'; /* replace white spaces with 0 */
*argv++ = line; /* save the argument position */
while (*line != '\0' && *line != ' ' &&
*line != '\t' && *line != '\n')
line++; /* skip the argument until ... */
}
*argv = '\0'; /* mark the end of argument list */
}
bool CheckForwardSlash(char temp[], int size)
{
bool present = false
for(int i = 0; i < size; i++){
if(temp[i] == '/'){
present = true;
break;
}
}
return present;
}
void execute(char **argv)
{
pid_t pid;
int status;
if ((pid = fork()) < 0) { /* fork a child process */
printf("*** ERROR: forking child process failed\n");
exit(1);
}
else if (pid == 0) { /* for the child process: */
if (execvp(*argv, argv) < 0) { /* execute the command */
printf("*** ERROR: exec failed\n");
exit(1);
}
}
else { /* for the parent: */
while (wait(&status) != pid) /* wait for completion */
;
}
}
void main(void)
{
char line[1024]; // The input line
char *argv[3]; // An array of pointers to the tokens (the tokens were parsed
// from the input line)
bool check1, check2 = false;
//A look-up table that contains some of the valid commands
char *LookUp[11] = {"emacs", "kill", "bye", "jobs", "fg", "chmod", "cd", "help", "cat", "cp"};
while (1) { // repeating....
printf("tish >> "); // the prompt
gets(line); // read in the command line
printf("\n");
parse(line, argv); // parse the line
if (strcmp(argv[0], "bye") == 0) // exit if the user enters bye
{exit(0);}
//Input Validation//
///////////////////
//If the input is just a white space character, continue with the next iteration of the loop
if (isspace(argv[0]))
continue; //If it is some sort of a white-space character,
//skip the current iteration of the while loop
//Call a function that checks for the validity of the input command
check2 = FunctionLookUp(argv, LookUp);
if(check2 == false){
fprintf("Invalid Command\n");
continue;
}
//Test argv[0] for invalid internal commands. Check for Letters and Negative numbers.
if(strcmp(argv[0], "kill") == 0){
if(isaplha(argv[1]) || atoi(argv[1]) < 0){
fprintf("Invald PID entered");
fprintf("Enter a positive numeric number");
continue;
}
}
int size = sizeof(argv[1]) + 1;
char temp[size];
strcpy(temp,agrv[1]);
check1 = CheckForwardSlash(temp, size);
//If true is returned by the CheckForwardSlash method, skip the rest of the while loop
if(check1 == true){
printf("Invalid file format\n");
printf("Avoid Forward Slashes in your file name\n");
continue;
}
//Input Validation Ends//
///////////////*********************//////////////////
//Signals to catch the Ctrl-C and Ctrl/ combination
signal(SIGINT, SIG_IGN); //The instructions said to ignore the SIGINT signal
signal(SIGTERM, SIG_DFL); //SIGTERM signal must be caught.
execute(argv); //Finally, execute the command
}
}
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