Issue with using execvp()

Question

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/wait.h>

extern int errno;

void parseArgs(char *path, char *argv[]) {
    while (*path != '\0') {
        while (*path == ' ' || *path == '\t' || *path == '\n') {
            *path++ = '\0';
        }
        *argv++ = path;
        while (*path != '\0' && *path != ' ' && *path != '\t' && *path != '\n') {
            path++;
        }
    }
    *argv = '\0';
}

int execArgs(char *argv[], int amp) {
    pid_t process;
    int check;

    if ((process = fork()) < 0) {
        fprintf(stderr, "Forking child failed\n%s\n", strerror(errno));
        errno = 0;
        return EXIT_FAILURE;
    } else if (process == 0) {
        if (execvp(*argv, argv) < 0) {
            fprintf(stderr, "Execution failed\n%s\n", strerror(errno));
            errno = 0;
            return EXIT_FAILURE;
        }
    } else {
        while (wait(&check) != process) {
            //do nothing
        }
    }
    return EXIT_SUCCESS;
}

int main (void) {
    char path[1024];
    char *argv[64];
    //int amp = 0;

    while (1) {
        printf("[root@localhost]$ ");
        fgets(path, 1024, stdin);
        puts("");
        parseArgs(path, argv);
        if (strcmp(argv[0], "exit") == 0) {
            return EXIT_SUCCESS;
        }
        execArgs(argv, 0);
    }
}

I'm having an issue here. The problem seems to be a parse error, because whenever I try to ls a directory, I get ls: cannot access : No such file or directory. The odd thing is, if I go ls .. I get:

ls: cannot access : No such file or directory
..:
cat  cat.c  cat.c~  m4

NOTE: The above are the contents of the dir one level up!

Furthermore - and I suspect the issues are linked - I cannot cd into directories, however I'm not 100% sure of this as it does not throw anything like directory does not exist; I just get a blank space (but my cwd does not update).

Any help would be appreciated!

For Reference, some test inputs

[thanasi@localhost m4]$ ./cli
[root@localhost /home/thanasi/Systems Programming/m4]$ ls

ls: cannot access : No such file or directory
[root@localhost /home/thanasi/Systems Programming/m4]$ ls ..

ls: cannot access : No such file or directory
..:
cat  cat.c  cat.c~  m4
[root@localhost /home/thanasi/Systems Programming/m4]$ cd test

[root@localhost /home/thanasi/Systems Programming/m4]$ cd /test           

/usr/bin/cd: line 2: cd: /test: No such file or directory
[root@localhost /home/thanasi/Systems Programming/m4]$ ^C

And confirmation dir 'test' does exist:

[thanasi@localhost m4]$ ls -al
total 36
drwxrwxr-x. 3 thanasi thanasi  4096 Mar 17 22:00 .
drwxrwxr-x. 3 thanasi thanasi  4096 Mar 17 20:36 ..
-rwxrwxr-x. 1 thanasi thanasi 13175 Mar 17 22:00 cli
-rw-rw-r--. 1 thanasi thanasi  1222 Mar 17 22:00 cli.c
-rw-rw-r--. 1 thanasi thanasi  1221 Mar 17 22:00 cli.c~
drwxr-xr-x. 2 root    root     4096 Mar 17 21:32 test

Answer 1

Typically, the input you got from fgets ends with a newline. Say you got {'l', 's', '\n', '\0'} as the first four bytes in path. Then, when parseArgs has set argv[0] to point to the first character in path, the next iteration overwrites the newline with '\0', and sets argv[1] = &path[2];:

void parseArgs(char *path, char *argv[]) {
    while (*path != '\0') {
        while (*path == ' ' || *path == '\t' || *path == '\n') {
            *path++ = '\0';
        }
        *argv++ = path;
        while (*path != '\0' && *path != ' ' && *path != '\t' && *path != '\n') {
            path++;
        }
    }
    *argv = '\0';
}

so your argv array contains a pointer to an empty string between the last real argument and the NULL terminating the array. Thus ls tries to list the contents of "" - which doesn't exist.

Since you can't be certain that the input you got from fgets ends with a newline, guard the assignment

if (*path) *argv++ = path;

to avoid that.