cd.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>

int cd(char **args)
{
    /* static local variable, to preserve the old pwd */
    static char *oldpwd;

    char *tmp = getcwd(NULL, 0);

    /* if called with no arguments, then chdir to $HOME */
    if (!args[1]) {
        if (chdir(getenv("HOME")) != 0) {
            perror("chdir($HOME)");
            return -1;
        }
    } else if (args[1][0] == '-' && args[1][1] == '\0') {
        /* if called with '-', then chdir to $OLDPWD */
        if (chdir(oldpwd) != 0) {
            perror("chdir($OLDPWD)");
            return -1;
        }
    } else {
        if (chdir(args[1]) != 0) {
            fprintf(stderr, "cd: %s: No such file or directory\n", args[1]);
            return -1;
        }
    }

    free(oldpwd);
    oldpwd = tmp;

    return 0;
}