How to implement history function? - c

Question

I am new to C programming and currently learning this into a course. I'm facing an issues while trying to practice the below history function.
I'm able to display the shell commands. However, when I type history, the past shell commands are not getting saved into the history buffer.
Can anyone help me to find where I went wrong?
Here is my code:
#include<stdio.h>
#include<unistd.h>
#include<string.h>
#define BUFSIZE 20
#define MAX_WORD_IN_LINE 20
int tokenize(char *str, char **args)
{
int i, argc = 0;
char *token;
token = strtok(str," \t\n");
for(i=0; token!=NULL;i++)
{
args[i] = token;
printf("args[%d] = %s\n", i, args[i]);
token = strtok(NULL, " \t\n");
argc++;
}
return argc;
}
void display_strings(char **p)
{
if (p == NULL) return;
while(*p != NULL){
printf("%s\n",*p);
p++;
}
}
int history(char *hist[], int current){
int i = current;
int hist_num = 1;
do {
if (hist[i]) {
printf("%4d %s\n", hist_num, hist[i]);
hist_num++;
}
i = (i + 1) % BUFSIZE;
} while (i != current);
return 0;
}
int main(void){
char *args[MAX_WORD_IN_LINE];
char buffer[BUFSIZE];
char *hist[BUFSIZE];
int i,current=0;
pid_t pid;
int argc;
for(i=0;i<BUFSIZE;i++)
hist[i]= NULL;
while(1) {
memset(args,0,MAX_WORD_IN_LINE);
printf("osh> ");
fgets(buffer, BUFSIZE, stdin);
argc = tokenize(buffer, args);
//display_strings(args);
// skip on empty command
if (argc == 0) continue;
if (strcmp(args[0],"quit") == 0) break;
else if (strcmp(args[0], "hello") == 0) printf("Hello there. How are you?\n");
else if (strcmp(args[0],"history")==0) history(hist,current);
else {
pid = fork();
if (pid == 0) {
hist[current]=strdup(args[0]);
current++;
execvp(args[0], args);
return 0;
}

Answer 1

You need to make a copy of the string that args[0] points to when you save it in hist. Currently, you're just assigning the pointer to the current args[0], and it will be overwritten by the next command. When you print the history, you'll just get the last command repeatedly. So use:
hist[current] = strdup(args[0]);