strcmp is not working the way it should
Revision 3
What is the return value of strcmp in c.I wrote the following code in c.
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/time.h>
#include <sys/resource.h>
#include<stdarg.h>
#define MAX 128
char *path = "/bin/";
char *argument[MAX];
char buffer[MAX];
int numberOfArguments;
pid_t pid;
int rv ;
char prog[128];
char parse(char buffer[],int i)
{
buffer[i] = '\0';
argument[0] = strtok(buffer, " ");
numberOfArguments = 1;
argument[numberOfArguments] = strtok(NULL, " ");
while (argument[numberOfArguments] != NULL) {
numberOfArguments++;
argument[numberOfArguments] = strtok(NULL, " ");
}
return numberOfArguments;
}
int changeDirectory( ){
int result = 0;
if (numberOfArguments > 2) {
printf("%s: Too many operands \nUsage: %s <pathname>\n", (char *) argument[0], (char *) argument[0]);
}
if(numberOfArguments == 1) {
const char* home = getenv("HOME");
int i = chdir(home);
if(i < 0)
printf("directory couldn't be changed\n");
else{
printf("directory changed\n");
printf("home = %s\n", home);
}
}
else {
result = chdir(argument[1]);
if(result == 0){
printf("directory changed\n");
exit(0);
}
else{
printf("Couldn't change directory to %4s", (char *)argument[1] );
}
}
return 0;
}
void forground(char buffer[], int i){
parse(buffer,i);
char prog[128];
strcpy(prog, path);
strcat(prog,argument[0]);
printf("%s\n",prog);
rv = execv(prog, argument);
}
int main(){
char *s;
while(1)
{
printf("myshell>> ");
int i = 0;
while ((i < MAX) && ((buffer[i] = getchar()) != '\n') && buffer[i] != EOF)
i++;
if (i == MAX) {
buffer[MAX-1] = '\0';
while (getchar() != '\n');
printf("argument too long\n");
}
else {
pid = fork();
if (pid != 0){
wait(NULL);
}
if (pid != 0) {
forground(buffer,i);
}
parse(buffer,i);
if (!strcmp(argument[0], "cd"))
changeDirectory();
else if (!strcmp(argument[0], "exit")) {
int ret;
ret = execl ("/bin/bash", "bash",(char *)0);
}
process();
}
}
return 0;
}
the out put is always Null after argv[0].That means some how it is loosing the input after "cd".Why is that does strcmp turn the other valus after cd to null???
Posted 11-Jan-13 1:07am
by
mimi from Unknown.