Hi all,
I have an assignment from school to write a shell program in linux. the idea is to exercise fork() and execv() functions.. the shell program is supposed to be the master and every command that the user prints will run in a new process. we also need to try running the command in every path from the enviroment variable PATH.
for some reason, the execv function isn't working.. any idea what i'm doing wrong?
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
int main()
{
pid_t pid;
char *sh="Shell>";
int i,pathindex=0, ret;
char line[80]; // getting the user prompt
char *paths[20]={"NULL"}; // 20 values path array
char *currentpath, *path; // current path to execute in
char *arg[]={NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL, NULL} ;
path=getenv("PATH");
currentpath=strtok(path,":");
while (currentpath!=NULL)
{
paths[pathindex]=currentpath; // filling the paths array
currentpath=strtok(NULL,":"); // from enviroment variable
pathindex++; // PATH.
}
system("/usr/bin/clear");
printf("\n\nShell Program (OS Course)\n");
printf("-------------------------\n\n");
while (1)
{
printf("%s",sh);
gets(line);
arg[0]=strtok(line," "); // getting command
if (strcmp(line,"leave")==0) exit(0);
for (i=1;i<10;i++) arg=strtok(NULL," "); //getting command arguments
pathindex=0;
while (paths[pathindex]!=NULL)
{
if ((pid=fork())<0)
{
printf("Error: Couldn't fork\n");
exit(1);
}
if (pid==0)
{
printf("trying to run %s in %s\n",arg[0],paths[pathindex]);
ret=execv(paths[pathindex],arg);
if (ret==-1) exit(1);
}
else { wait(); pathindex++; }
}
}
return 0;
}