text: /*-*- mode:c;indent-tabs-mode:nil;c-basic-offset:2;tab-width:8;coding:utf-8 -*-│
  │vi: set net ft=c ts=2 sts=2 sw=2 fenc=utf-8                                :vi│
  ╞══════════════════════════════════════════════════════════════════════════════╡
  │ Copyright 2020 Justine Alexandra Roberts Tunney                              │
  │                                                                              │
  │ Permission to use, copy, modify, and/or distribute this software for         │
  │ any purpose with or without fee is hereby granted, provided that the         │
  │ above copyright notice and this permission notice appear in all copies.      │
  │                                                                              │
  │ THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL                │
  │ WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED                │
  │ WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE             │
  │ AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL         │
  │ DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR        │
  │ PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER               │
  │ TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR             │
  │ PERFORMANCE OF THIS SOFTWARE.                                                │
  ╚─────────────────────────────────────────────────────────────────────────────*/
  #include "libc/bits/safemacros.internal.h"
  #include "libc/calls/calls.h"
  #include "libc/mem/mem.h"
  #include "libc/runtime/runtime.h"
  #include "libc/str/str.h"
  
  /**
   * Replaces tilde in path w/ user home folder.
   *
   * @param path is NULL propagating
   * @return must be free()'d
   */
  char *replaceuser(const char *path) {
    char *res, *p;
    const char *home;
    size_t pathlen, homelen;
    res = NULL;
    if (path && *path++ == '~' && !isempty((home = getenv("HOME")))) {
      while (*path == '/') path++;
      pathlen = strlen(path);
      homelen = strlen(home);
      while (homelen && home[homelen - 1] == '/') homelen--;
      if ((p = res = malloc(pathlen + 1 + homelen + 1))) {
        p = mempcpy(p, home, homelen);
        *p++ = '/';
        memcpy(p, path, pathlen + 1);
      }
    }
    return res;
  }
  