Question

This is the output of the following code, but I expect it to be correct paths.
What is wrong in the output of odd indexes such as pathsarray[1] = ls/ls ?

---/usr/lib/lightdm/lightdm/ls
---ls/ls
---/usr/local/bin/ls
---ls/ls
---/usr/bin/ls
---ls/ls
---/bin/ls
---ls/ls

char *pathsarray[MAXARGS];//path
char *path=getenv("PATH");
tokenizeEnvPaths(path);

int i;

for(i=0;i<MAXARGS;i++)
{
    if(pathsarray[i] != NULL)
    {
        strcat(pathsarray[i],"/");
        strcat(pathsarray[i],"ls");
        fprintf(stderr,"---%s\n",pathsarray[i]);
    }


}

Answer 1

Here’s an SSCCE (Short, Self-Contained, Correct Example).

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

enum { MAXARGS = 32 };
enum { MAXPATHLEN = 1024 };

char *pathsarray[MAXARGS];

static void add_path(char **dir, const char *begin, const char *end)
{
    if (end == begin)
    {
        begin = ".";
        end = begin + 1;
    }
    size_t len = end - begin;
    *dir = malloc(len + 1);
    memmove(*dir, begin, len);
    (*dir)[len] = '\0';
    printf("Found: %s\n", *dir); // Debug
}

/* Split path into components - ignore empty elements */
static size_t tokenizeEnvPaths(const char *path, char **dirs, size_t max_dirs)
{
    const char *begin = path;
    const char *end;
    size_t num_dirs = 0;

    while (num_dirs < max_dirs && (end = strchr(begin, ':')) != 0)
    {
        add_path(&dirs[num_dirs++], begin, end);
        begin = end + 1;
    }
    if (num_dirs < max_dirs && *begin != '\0')
        add_path(&dirs[num_dirs++], begin, begin + strlen(begin));
    return num_dirs;
}

int main(void)
{
    const char *path = getenv("PATH");
    size_t ndirs = tokenizeEnvPaths(path, pathsarray, MAXARGS);

    for (size_t i = 0; i < ndirs; i++)
    {
        if (pathsarray[i] != NULL)
        {
            char buffer[MAXPATHLEN];
            snprintf(buffer, sizeof(buffer), "%s/%s", pathsarray[i], "ls");
            fprintf(stderr, "---%s\n", pathsarray[i]);
        }
    }
    return(0);
}

Example output:

$ PATH=:$PATH ./sp
Found: .
Found: /Users/jleffler/bin
Found: /usr/informix/11.70.FC6/bin
Found: /usr/gcc/v4.7.1/bin
Found: /usr/informix/11.70.FC6
Found: /Users/jleffler/perl/v5.16.0/bin
Found: /usr/local/bin
Found: /usr/bin
Found: /bin
Found: /usr/gnu/bin
Found: /usr/sbin
Found: /sbin
---./ls
---/Users/jleffler/bin/ls
---/usr/informix/11.70.FC6/bin/ls
---/usr/gcc/v4.7.1/bin/ls
---/usr/informix/11.70.FC6/ls
---/Users/jleffler/perl/v5.16.0/bin/ls
---/usr/local/bin/ls
---/usr/bin/ls
---/bin/ls
---/usr/gnu/bin/ls
---/usr/sbin/ls
---/sbin/ls
$