Bad 'ls' Command Behavior In Custom Simple Shell - c

Question

I am having an issue that is just seeming to slip past my knowledge. I am writing a simple shell to learn some systems programming for an internship coming up with Unisys. In my shell, it seems that all of the commands I am trying are working besides the ls and even now discovering the wc command. ls and wc works when I type it by itself, but if I give it arguments, it will fail to work and give me an error saying No such file or directory.
here is my code:
#include <sys/types.h>
#include <sys/wait.h>
#include <errno.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sysexits.h>
#include <unistd.h>
#define BUF_SIZE 1024
#define DELIMS " -\r\t\n"
/****************************************************************
* Capture input from the user. Returns the input from the
* standard input file descriptor.
***************************************************************/
char * getInput (char **buffer, size_t buflen)
{
size_t bufsize = BUF_SIZE;
*buffer = malloc(sizeof(char) * bufsize + 1); // allocate space for the buffer
if (!*buffer)
{
fprintf(stderr, "Shell: buffer allocation error\n");
exit(EXIT_FAILURE);
}
printf("$$ ");
fflush(NULL);
int bytesRead = getline(&(*buffer), &bufsize, stdin);
if (bytesRead < 0)
{
printf("Getline error\n");
exit(EXIT_FAILURE);
}
return *buffer; // Not capturing return value right now
}
/****************************************************************
* Tokenize the buffer input from stdin
***************************************************************/
char ** splitLine(char *line)
{
int bufsize = BUF_SIZE;
int pos = 0;
char **tokens = malloc (sizeof(char) * BUF_SIZE + 1);
char *token;
if (!tokens)
{
fprintf(stderr, "Shell: buffer allocation error\n");
exit(EXIT_FAILURE);
}
/* Tokenize the line */
token = strtok(line, DELIMS);
while (token != NULL)
{
tokens[pos] = token;
pos++;
if (pos > bufsize)
{
bufsize += BUF_SIZE;
tokens = realloc(tokens, bufsize * sizeof(char) + 1);
if (!tokens)
{
fprintf(stderr, "Shell: buffer allocation error\n");
exit(EXIT_FAILURE);
}
}
token = strtok(NULL, DELIMS); // continue grabbing tokens
}
tokens[pos] = NULL;
return tokens;
}
/****************************************************************
* Main function
***************************************************************/
int main (int argc, char **argv)
{
char *buf; // buffer to hold user input from standard input stream.
pid_t pid; // Parent id of the current process
int status;
/* Loop while the user is getting input */
while (getInput(&buf, sizeof(buf)))
{
char **args = splitLine(buf);
int i = 0;
/* Print tokens just to check if we are processing them correctly */
while (1)
{
char *token = args[i++];
if (token != NULL)
printf("Token #%d: %s\n", i, token);
else
break;
}
fflush(NULL);
/* Fork and execute command in the shell */
pid = fork();
switch(pid)
{
case -1:
{
/* Failed to fork */
fprintf(stderr, "Shell cannot fork: %s\n", strerror(errno));
continue;
}
case 0:
{
/* Child so run the command */
execvp(args[0], args); // Should not ever return otherwise there was an error
fprintf(stderr, "Shell: couldn't execute %s: %s\n ", buf, strerror(errno));
exit(EX_DATAERR);
}
}
/* Suspend execution of calling process until receiving a status message from the child process
or a signal is received. On return of waitpid, status contains the termination
information about the process that exited. The pid parameter specifies the set of child
process for which to wait for */
if ((pid = waitpid(pid, &status, 0) < 0))
{
fprintf(stderr, "Shell: waitpid error: %s\n", strerror(errno));
}
free(args);
}
free(buf);
exit(EX_OK);
}
For example, I have tried the following commands with output:
ls -la (THE ISSUE)
$$ ls -la
Token #1: ls
Token #2: la
ls: la: No such file or directory
$$
wc -l (THE ISSUE)
$$ wc -l
Token #1: wc
Token #2: l
wc: l: open: No such file or directory
ls
$$ ls
Token #1: ls
Makefile driver driver.dSYM main.c main.o
$$
ps -la
$$ ps -la
Token #1: ps
Token #2: la
UID PID PPID CPU PRI NI VSZ RSS WCHAN STAT TT TIME COMMAND
0 2843 2405 0 31 0 2471528 8 - Us s000 0:00.08 login
501 2845 2843 0 31 0 2463080 1268 - S s000 0:01.08 -bash
501 4549 2845 0 31 0 2454268 716 - S+ s000 0:00.01 ./driv
0 4570 4549 0 31 0 2435020 932 - R+ s000 0:00.00 ps la
$$
which which
$$ which which
Token #1: which
Token #2: which
/usr/bin/which
which -a which
$$ which -a which
Token #1: which
Token #2: a
Token #3: which
/usr/bin/which
and even finally man getline
GETLINE(3) BSD Library Functions Manual GETLINE(3)
NAME
getdelim, getline -- get a line from a stream
LIBRARY
Standard C Library (libc, -lc)
.
.
.
Can anybody help me point out why I am having this issue?

Answer 1

Youve added "-" as a word seperator in the DELIMS macro.
Removing it should fix your problem.
As an aside, its probably best to avoid macros where you can do so easily. Here, I would have used a const char* delims to store the separators. I usually find it easier to declare a variable close to where its used - I think that makes it easier to spot bugs and read the code.