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

int main ()
{
        char * buffer;
        char * result = NULL;
        char * com = NULL;
        int code = 0;
        buffer = getenv ("PATH");
        char response[512];
        fgets(response, 100, stdin);
        response[strlen(response)-1] = NULL;

        printf (">> Current path is: %s\n\n",buffer);
        result = strtok(buffer,":");
        if (buffer!=NULL)
        {
                while(result!=NULL)
                {
                        //printf("Searching in %s\n", result);
                        com = strcat(result, "/");
                        com = strcat(com, response);
                        printf("Searching for %s\n", com);
                        code = access(com, F_OK);
                        if(code == 0)
                        {
                                printf("Found at %s!\n", result);
                                break;
                        }
                        result = strtok(NULL, ":");
                }
        }
        return 0;
}

output:
wizo@alphak ~/Work/2nd Year/OS/lab2 $ ./pathtest
ls
>> Current path is: /usr/local/bin:/usr/bin:/bin:/opt/bin:/usr/i386-pc-linux-gnu/gcc-bin/3.4.4

Searching for /usr/local/bin/ls
Searching for ls/ls
Searching for /ls/ls
Searching for /ls/ls
Searching for /ls/ls
<repeats till seg faults>
-------------------------------------------------------------------------------------------

int main ()
{
        char * buffer;
        char * result = NULL;
        char * com = NULL;
        int code = 0;
        buffer = getenv ("PATH");
        char response[512];
        fgets(response, 100, stdin);
        response[strlen(response)-1] = NULL;

        printf (">> Current path is: %s\n\n",buffer);
        result = strtok(buffer,":");
        if (buffer!=NULL)
        {
                while(result!=NULL)
                {
                        printf("Searching in %s\n", result);
                        /*com = strcat(result, "/");
                        com = strcat(com, response);
                        printf("Searching for %s\n", com);
                        code = access(com, F_OK);
                        if(code == 0)
                        {
                                printf("Found at %s!\n", result);
                                break;
                        }*/
                        result = strtok(NULL, ":");
                }
        }
        return 0;
}

output:

wizo@alphak ~/Work/2nd Year/OS/lab2 $ !./
./pathtest
ls
>> Current path is: /usr/local/bin:/usr/bin:/bin:/opt/bin:/usr/i386-pc-linux-gnu/gcc-bin/3.4.4

Searching in /usr/local/bin
Searching in /usr/bin
Searching in /bin
Searching in /opt/bin
Searching in /usr/i386-pc-linux-gnu/gcc-bin/3.4.4