mkpath.c

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

static void make_path(const char *path);
static void die(const char *s);

int
main(int argc, char *argv[])
{
    int i;

    if (argc < 2) {
        fprintf(stderr, "%s: no arguments\n", argv[0]);
        exit(1);
    }
    for (i = 1; i < argc; i++) {
        make_path(argv[i]);
    }
    exit(0);
}

/*
    "Check & Create" strategy may fail in multi-process environment,
    we try to create a directory and check an error instead.
*/
static void
make_path(const char *path)
{
    if (mkdir(path, 0777) == 0) {
        // Successfully created.  OK
        return;
    }
    if (errno == EEXIST) {
        struct stat st;
        if (stat(path, &st) < 0) die("stat");
        if (!S_ISDIR(st.st_mode)) {
            fprintf(stderr, "file exists but is not a directory: %s\n", path);
            exit(1);
        }
        // Given path is already a directory.
        return;
    }
    else if (errno == ENOENT) {
        // Parent path is not a directory.  Make it
        char *parent_path = strdup(path);
        if (!parent_path) die("strdup");

        // Removes duplicated trailing slashes ('/')
        char *last = parent_path + strlen(parent_path) - 1;
        while (*last == '/' && last != parent_path) {
            *last-- = '\0';
        }

        if (strcmp(parent_path, "/") == 0) {
            fprintf(stderr, "error: root directory is not a directory???\n");
            exit(1);
        }

        char *sep = strrchr(parent_path, '/');
        if (!sep) {
            // No slash ('/') found.  e.g. "component"
            fprintf(stderr, "error: current directory is not a directory???\n");
            exit(1);
        }
        else if (sep == parent_path) {
            // e.g. "/component"
            fprintf(stderr, "error: root directory is not a directory???\n");
            exit(1);
        }
        // e.g. "/a/b/c" -> "/a/b\0c"
        *sep = '\0';

        make_path(parent_path);
        if (mkdir(path, 0777) < 0) die(path);
        return;
    }
    else {
        perror(path);
        exit(1);
    }
}

static void
die(const char *s)
{
    perror(s);
    exit(1);
}